brake failure

[Marian]

So here I am riding on impossible dirt roads in the rain in Guangxi
province and my brakes have just stopped working. At least at the
beginning I was able to deal with this on some of the gentler
downhills by doing a Fred Flintstone with my left foot while I was
riding and later on I figured out that if I got up off the saddle and
sat on the top tube pulling on the brake cable I could slow myself
still farther but the brakes are just refusing to stop the bike.

I've done a cursory inspection, cleaned them, tightened them, loosened
them, tightened them, moved things, moved things back, spun the wheel
up, pulled on the brake lever and all I get is a scthscthscth noise
which gradually results in the wheel slowing down but not really
stopping. And this when nothing is on the bike.

They worked fine yesterday.

Heck, they worked fine this morning.

It was just when the rain and the mud started getting bad (along about
the same time that the really bad downhills stopped but around the
same time that the road condition deteriorated further) that this
happened. The levers still squeeze but the wheels don't stop
anymore. The person who was riding with me on a mountain bike (who
has since gone home) had the same kind of V-brakes as my front brake
(plain jane no name Shimano) and I've got Deore for my rear brake with
original brake pads that are nowhere near the wear line (only about
700km old).

What happened?

What can I do about it?

-M

[Martin Borsje]

Tom Kunich expressed precisely :
>
> For what it's worth, I've found the Dutch and Belgians seem able to speak
> more languages with less accent than even the Swiss.

The Swiss have one common language: "money".

[A Muzi]

>>> "M-gineering" <ikmotgeenspam@m-gineering.nl> wrote
>>>> Are the brakes setup so that the noodle bottoms out against the
>>>> clampbolt on the V-s? Check that there is sufficient space, if not
>>>> change the washers on the brakeblock holder around
>>
>> Tom Kunich wrote:
>>> I'm certainly glad that I'm not practicing engineering in the
>>> Netherlands where they apparently speak some sort of foreign
>>> language...... :-)

> "A Muzi" <am@yellowjersey.org> wrote
>> huh.
>> That seemed quite clear (and sorta good advice BTW) to me. It's both a
>> real and a common problem.
>>
>> I already suggested cantilevers rather than linear brakes to her weeks
>> ago but those weren't readily available to her. Linear ("V") brakes
>> are more prone to crud embedding and have rapid pad and rim wear. That
>> goes double in dirt and rain.

Tom Kunich wrote:
> Come on Andy, you'd think I didn't put a smiley on that. As a matter of
> fact I'm and engineer and some of the best engineers I've worked with
> were Dutch.
>
> But what is a "noodle" which "bottoms out on the clampbolt of the V's"?
> It appears to me as if he did a straight translation from Dutch to
> English and of course the names of things don't quite match up. That's
> what I found humorous and not the fact that he didn't know what he was
> talking about.

> For what it's worth, I've found the Dutch and Belgians seem able to
> speak more languages with less accent than even the Swiss.

Oh, I wasn't going anywhere with the humor, but* linear brakes do have
noodles and and, when the pad spacing is screwed up, the noodle really
does hit the cable clamping bolt before braking. On your Campagnolo
calipers this is not a problem!

*for other readers who may be curious
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[Nate Nagel]

Tom Kunich wrote:
> "A Muzi" <am@yellowjersey.org> wrote in message
> news:f1fe1$4830773c$21269@news.teranews.com...
>
>>> "M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
>>> news:g0p7uf$afe$1@localhost.localdomain...
>>>
>>>> Are the brakes setup so that the noodle bottoms out against the
>>>> clampbolt on the V-s? Check that there is sufficient space, if not
>>>> change the washers on the brakeblock holder around
>>
>>
>> Tom Kunich wrote:
>>
>>> I'm certainly glad that I'm not practicing engineering in the
>>> Netherlands where they apparently speak some sort of foreign
>>> language...... :-)
>>
>>
>> huh.
>> That seemed quite clear (and sorta good advice BTW) to me. It's both a
>> real and a common problem.
>>
>> I already suggested cantilevers rather than liner brakes to her weeks
>> ago but those weren't readily available to her. Linear ("V") brakes
>> are more prone to crud embedding and have rapid pad and rim wear. That
>> goes double in dirt and rain.
>
>
> Come on Andy, you'd think I didn't put a smiley on that. As a matter of
> fact I'm and engineer and some of the best engineers I've worked with
> were Dutch.
>
> But what is a "noodle" which "bottoms out on the clampbolt of the V's"?
> It appears to me as if he did a straight translation from Dutch to
> English and of course the names of things don't quite match up. That's
> what I found humorous and not the fact that he didn't know what he was
> talking about.
>
> For what it's worth, I've found the Dutch and Belgians seem able to
> speak more languages with less accent than even the Swiss.
>

The "noodle" is the little curved tube of metal that goes on the end of
the brake cable housing. That's the only one-word name I've heard for
it. Otherwise, it's "that little curved metal tube."

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[Andrew Price]

On Sun, 18 May 2008 13:01:55 -0700, "Tom Kunich" <cyclintom@yahoo.
com> wrote:

[---]

>For what it's worth, I've found the Dutch and Belgians seem able to speak
>more languages with less accent than even the Swiss.

"Even the Swiss"? You've never heard the Swiss speaking German or
French? They have an accent you can spot a mile away.

[Martin Borsje]

Tom Kunich expressed precisely :
>
> For what it's worth, I've found the Dutch and Belgians seem able to speak
> more languages with less accent than even the Swiss.

The Swiss have one common language: "money".

[A Muzi]

>>> "M-gineering" <ikmotgeenspam@m-gineering.nl> wrote
>>>> Are the brakes setup so that the noodle bottoms out against the
>>>> clampbolt on the V-s? Check that there is sufficient space, if not
>>>> change the washers on the brakeblock holder around
>>
>> Tom Kunich wrote:
>>> I'm certainly glad that I'm not practicing engineering in the
>>> Netherlands where they apparently speak some sort of foreign
>>> language...... :-)

> "A Muzi" <am@yellowjersey.org> wrote
>> huh.
>> That seemed quite clear (and sorta good advice BTW) to me. It's both a
>> real and a common problem.
>>
>> I already suggested cantilevers rather than linear brakes to her weeks
>> ago but those weren't readily available to her. Linear ("V") brakes
>> are more prone to crud embedding and have rapid pad and rim wear. That
>> goes double in dirt and rain.

Tom Kunich wrote:
> Come on Andy, you'd think I didn't put a smiley on that. As a matter of
> fact I'm and engineer and some of the best engineers I've worked with
> were Dutch.
>
> But what is a "noodle" which "bottoms out on the clampbolt of the V's"?
> It appears to me as if he did a straight translation from Dutch to
> English and of course the names of things don't quite match up. That's
> what I found humorous and not the fact that he didn't know what he was
> talking about.

> For what it's worth, I've found the Dutch and Belgians seem able to
> speak more languages with less accent than even the Swiss.

Oh, I wasn't going anywhere with the humor, but* linear brakes do have
noodles and and, when the pad spacing is screwed up, the noodle really
does hit the cable clamping bolt before braking. On your Campagnolo
calipers this is not a problem!

*for other readers who may be curious
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[jobst.brandt@stanfordalumni.org]

Andrew Muzi wrote:

>>> I already suggested cantilevers rather than liner brakes to her
>>> weeks ago but those weren't readily available to her. Linear
>>> ("V") brakes are more prone to crud embedding and have rapid pad
>>> and rim wear. That goes double in dirt and rain.

>> Are you blaming the pads or the mechanics of the linear brake?

>> My current touring/commuting bike has cantilever brakes that use
>> "V" type pad (lots of surface area but thin.) For what it's worth,
>> I do find the pads wear quickly. Given that I ride in rain, snow,
>> salt, etc, that's to be expected, and at $4 a pair, I'm not too
>> broken up about it. What I really love is that I can change them
>> out without having to reset the brakes, something I never liked
>> about traditional cantilever brakes with smooth stud shoes.

> Although Kool Stop pads are better than OEM (also not readily
> available to Marian), linear systems promote rapid rim wear and seem
> to be more prone to crud in the pads - whether it jams in faster or
> just scrapes rim chunks into the pad faster I can't say.

Having had many years to research brakes, starting with Universal,
pre-Campagnolo brakes, Weinmann, and various centerpull calipers, I
searched for several effects: 1) Embedded grit in pads, 2) Hand lever
braking force required and 3) brake pad wear rate. In that pursuit I
also measured mechanical advantage of various brakes and discovered
that contrary to he bicycling press, all calipers had a 1:1 ratio and
hand levers had 4:1. That is, the mechanical advantage was the same
for all brakes (Including Campagnolo when they took over the high
quality end of the business and having an excellent QR.

What I found was that Kool-Stop Salmon pads were the best, Campagnolo
a distant second, and Mafac, horrible in that they always chewed up
rims. Universal didn't come off well either. The most striking
feature of Kool-Stop pads was that even when riding through wet dirt
and picking up road mud and grit, the pads would clear themselves once
back on pavement by merely pumping the brake hard.

Not being one to worry about fashion and having a line of
practicality, I chose the Continental model because, unlike inserts
(typically in Campagnolo and Universal brakes) these pads could not be
accidentally knocked out of the pad holder when inserting a wheel,
something I observed happening a few times to the surprise of a rider
after a wheel change.

High pitch squeal is mainly caused by contamination on the braking
surface, mainly humidity, but also from soft drink splash or even
urine from roadside relief while standing astride the bicycle. Squeal
can be cleared up by heavy braking on a steep descent that gets rims
hot. It is not a matter of pad toe-in as is often claimed.

Just the same, toe-in occurs naturally because when braking hard
caliper arms bend forward in a way that makes the rear of the pad wear
faster than the forward end. I suppose someone noticed that well worn
pads seldom squealed AND that they had toe-in, which led to brutal
deformation of brake calipers. If this were a manually added feature,
then it should be added by running a rasp lengthwise across the brake
pad, not by bending brake calipers.

http://www.koolstop.com/brakes/index.php
--
Jobst Brandt

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> Carl Fogel wrote:
>
>>>>>> That's all generally helpful but the specific bike here has
>>>>>> linear ("V") brakes, which not only have a ratio with greater
>>>>>> cable travel and greater pressure at the rim for a given effort
>>>>>> at the lever, but are notorious for chewing rims and pads.
>
>>>>> Maybe you can tell me what is "linear" about these brakes and
>>>>> what the MA (mechanical advantage) is. Appearances can
>>>>> deceive. It was once believed that centerpull brakes had twice
>>>>> the MA of sidepull calipers based on the length of caliper input
>>>>> levers on which the straddle cable acts. This ignored that there
>>>>> are two of these, which divides that apparent MA in two. Other
>>>>> than these considerations, more pad force does not affect whether
>>>>> they develop grit or not.
>
>>>> "Linear" a.k.a. "Direct Pull" a.k.a. "V" type brakes really are
>>>> different from all other cable actuated bicycle brakes. Here are
>>>> the lurid details, provided by Sheldon from beyond the grave:
>
> http://www.sheldonbrown.com/canti-direct.html
>
>>> Sheldon isn't able to explain that maze of words today, in the
>>> absence of picture or reasonable proof that the mechanical
>>> advantage is significantly higher or lower between one brake and
>>> another, nor how these differences were measured or verified.
>
>> This may be what you're looking for:
>
> http://sheldonbrown.com/cantilever-geometry.html
>
> It is NOT. The combination of cable yoke angles and brake lever
> angles is highly confusing to most people.

"some people" = you.


> For that reason, measuring
> hand lever stroke and combined pad(s) stroke is the only unambiguous
> measure of MA. The article by Sheldon is as vague as claims by brake
> manufacturers.

rubbish jobst. the math is clear and unambiguous.

[A Muzi]

> "travis.harry@gmail.com" <travis.harry@gmail.com> wrote:
>> One can find online--trust me--a more recent review of perhaps 8
>> different replacement brake pads done by a British bicycling mag. I
>> cannot recall the testing methodology. But the design included
>> testing wet and dry separately and reporting braking distance as well
>> as remarks on aluminum extracted from the rims by the different
>> pads.. I found troubling the substantial negative rank order
>> correlation between wet and dry performance. Not perfectly negative,
>> but high enough that you would not pick out one pad as a reasonable
>> compromise, sacrificing just a little performance in one condition to
>> achieve high performance in the other.

Tim McNamara wrote:
> Years ago, VeloNews compared a variety of brake pads using the old
> Schwinn brake testing rig (basically a flywheel with a rim attached,
> mounted in a fork). Wet and dry performance was tested. The Kool Stop
> salmon material came out the best in both categories, as I recall.
> VeloNews used to have this report posted on their Web site. Maybe
> someone can ferret it out again.

There may be a difference in aluminum flaking on real rims as opposed to
a steel disc but it likely has value anyway.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> Larry Dickman wrote:
>
>>> To make up for that, their long thin pads wear out faster and have
>>> no benefit other than being different from other brakes.
>
>> V brake pads are much easier to install and align than any canti
>> brake I had before.
>
> Why? I don't see what their length and thinness

jobst, precisely /where/ do you see "length and thinness" in the words:
"V brake pads are much easier to install and align than any canti brake
I had before."???

what makes them easier to install and align is the design of mounting
post. nothing to do with "length and thinness".

> has to do with
> installation. My Kool-Stop Continental pads are as simple as can be
> and they last a long time.

your experience buffer overran 30 years ago. you comprehension buffer
is "status unknown".

[dabac]

Tom Kunich Wrote:
>
> A lot of people simply install the linear brake onto a normal touring
> bike
> and retain the original levers. I've done that myself, on 2-3 occasions. Worked rather well for the
front brake. Brake got a bit more powerful, but that frequently warned
for lock-up and endo repeatedly failed to happen.
Set-up for the rear was considerably more questionable, with extreme
care needed to keep the slack down enough to get both a drag free
resting position and a satisfying wheel lock w/o the lever bottoming out
against the bar.

You're quite right in that mismatched systems works, but at the cost of
becoming more finicky.
I've toyed with the idea of trying the set-up again using Nokon cables,
see if that would offer any improvement.
I also considered using the shifter cable from an old Positron RD to
see if that would reduce the slack enough to get decent performance out
of the rear brake, as according to the yachting world a solid wire is
less springy than a multi strand wire(for a given diameter).
Now when I've got matching sets it doesn't seem worth the effort merely
for satisfying my own curiosity though.

As a curiosity I can mention that my brother had a bike equipped with a
set of brake levers that had a set intermediate stroke length. Long
enough to let them work with rear linear brakes w/o bottoming out too
badly, but short enough not to be impossibly stiff when used with
cantis. Only seen that one pair though.


--
dabac

[jim beam]

carlfogel@comcast.net wrote:
> On May 19, 5:44�pm, jobst.bra...@stanfordalumni.org wrote:
>> Andrew Muzi wrote:
>>>>> That's all generally helpful but the specific bike here has linear
>>>>> ("V") brakes, which not only have a ratio with greater cable
>>>>> travel and greater pressure at the rim for a given effort at the
>>>>> lever, but are notorious for chewing rims and pads.
>>>> Maybe you can tell me what is "linear" about these brakes and what
>>>> the MA (mechanical advantage) is. �Appearances can deceive. �It was
>>>> once believed that centerpull brakes had twice the MA of sidepull
>>>> calipers based on the length of caliper input levers on which the
>>>> straddle cable acts. �This ignored that there are two of these,
>>>> which divides that apparent MA in two.
>>>> Other than these considerations, more pad force does not affect
>>>> whether they develop grit or not.
>>> "Linear" a.k.a. "Direct Pull" a.k.a. "V" type brakes really are
>>> different from all other cable actuated bicycle brakes. �Here are
>>> the lurid details, provided by Sheldon from beyond the grave:
>> �http://www.sheldonbrown.com/canti-direct.html
>>
>> Sheldon isn't able to explain that maze of words today, in the absence
>> of picture or reasonable proof that the mechanical advantage is
>> significantly higher or lower between one brake and another, nor how
>> these differences were measured or verified. �
>
> [snip]
>
>> Jobst Brandt
>
> Dear Jobst,
>
> This may be what you're looking for:
>
> http://sheldonbrown.com/cantilever-geometry.html
>
> Cheers,
>
> Carl Fogel

thank you carl. the section titled: "Mechanical Advantage of
Cantilevers" is particularly relevant.

[jobst.brandt@stanfordalumni.org]

clare who? wrote:

>>> I asked what the effective MA of the brake is from hand lever to
>>> brake pad and what brake pad and what made it "linear".

OK, how much more linear and how about a graph of had lever motion vs
pad motion comparing the most common brakes.

> What makes it linear?

> The mechanical advantage does not change with either the position of
> the brake handle, or the position of the pad. Moving the handle the
> first 1/16" moves the pads the same distance as the last 1/16"
> (within a VERY small variance - so small as to be inconsequential)
> This is NOT true of a center-pull or a cantilever because the angle
> of the pull changes in an "arc" both at the handle end and at the
> "caliper" end. Worse yet, the non-linearity ADDS instead of
> canceling. The dual pivot "linear pull" handles pull straight - as
> does the "V" brake "caliper".

Show how much this is on a graph.

> Really quite a simple concept.

Not simple at all. Just recall how long it took the concept of the
Dual Pivot brake to be even partly understood and why two pivots.

We aren't getting any closer to the answer of MA or linearity.

Jobst Brandt

[jim beam]

jobst.brandt@stanfordalumni.org, although we have to wonder how he ever
graduated, wrote:
> someone wrote:
>
>>> How much stretch did you measure in the cables?
>
>> Well, it did stretch enough for the rear brake lever to routinely
>> bottom out against the bar if the brake was set up for decent mud
>> clearance when I was running cantis. W/o a similar setup
>> immediately at hand to compare with I'd have to guess - 3 mm
>> perhaps. Lock-up was well within reach of the barrel adjuster - as
>> long as you were willing to accept a significant drag.
>
>> I'll have a look in the parts bin tomorrow - it might just be that I
>> didn't have the heart to throw away an uncut and barely used length
>> of cable despite the poor results it was giving.
>
> I don't see how cable stretch can be determined from hand lever
> motion.

eh?


> As was mentioned, caliper arms act in bending against
> elastomeric brake pads, causing elasticity in brake response.

actually jobst, you know how the rear brake system is more elastic than
the front? well, that's 100% because of cable/cable run elasticity.
the pads cancel out of that equation.

> Next
> time try bringing brake pads into firm contact with the rim and
> determine how much cable movement occurs where it leaves the housing
> anchor, compared to cable motion at the hand lever. That test occurs
> at the higher cable tension portion of brake application.
>


typical ill-considered presumptive jobstian nonsense. the pads, because
of low force per area, won't deflect much. a nice long cable run otoh
most definitely will. as will calipers, levers, and even frames where
the brakes are cantilever.

again, check lever displacement per unit force comparison between front
and rear. with caliper brakes, that easily determined differential is
simply cable elasticity.

[jim beam]

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:FcKdnV-aepmWkqPVnZ2dnUVZ_qXinZ2d@speakeasy.net...
>>
>> here's /your/ bottom line - you're focused on form, not content.
>> jobst is incorrect when he attributes braking elasticity solely to
>> "elastomeric brake pads".
>
> Hmm, and all this time I thought that he attributed it to elastic outer
> cable covers AND elastomeric pads. By the way, me too.

then you didn't read what i said!!! identical calipers, pads, levers,
different cables, front and rear. the rear lever /always/ get more
displacement, and that is /entirely/ due to the greater elasticity of
the longer cable. jobst says observed elasticity is only "elastomeric
brake pads". it's not, and the above proves it! sheesh.


>
> Jobst has many negatives in his corner for sure, but he has an
> overwhelming positive - he actually knows what he's talking about.

jobst's talent is writing for the peanut gallery in terms that they
believe, regardless of actual accuracy. you've just proved to be a case
in point.

[Tom Kunich]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:rsednQT974QbdaHVnZ2dnUVZ_jKdnZ2d@speakeasy.ne t...
> Tom Kunich wrote:
>>
>> When did you developed the ability to tell the difference between 15
>> ft/lbs and 17 ft/lbs of force manually?
>
> the day i got a fisherman's spring balance. you know, the type you weigh
> your bike with.
>
> btw, your unflagged snippage renders the context somewhat misconstructed.

Here's the bottom line - you don't like Jobst and you will simply attack him
under any circumstances and you will make up anything in order to attack
him. There doesn't seem to be any point in trying to discuss anything with
you because you simply want an adversarial relationship on this group.

[Tim McNamara]

In article
<942c3a7a-bd1b-42ea-b972-b9646faaf1e1@27g2000hsf.googlegroups.com>,
JG <jchg@cox.net> wrote:

> > This is, however, a tech newsgroup and therefore there are some
> > expectations of accuracy and precision.
>
> To be precise and accurate, "some" means more than zero.

Indeed. Unfortunately in the context of my statement the degree of
accuracy and precision to be expected is not quantifiable. Nor was that
necessary for my intent, which simply to contradict Tom Kunich's
suggestion that accuracy and precision are alien to the Internet or to
Usenet. In this case your comment was directed more to precision than
accuracy.

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> someone wrote:
>
>>> I don't see how cable stretch can be determined from hand lever
>>> motion.
>
>> If "nothing" else changes in either set-up or riding conditions
>> other than a switch from cable A to cable B, then what other reasons
>> are there for not getting wheel lock prior to bottoming out with one
>> cable when it turns out to be consistently possible with another?
>
> Without some background and measurements, this is the same old story
> that lets riders bel;ieve in cable stretch.

jobst, this is not faith, it's fact: it's _impossible_ to load anything
without some degree of deformation. the question then is, to what
extent does it happen?


> I have not seen it in
> many years of bicycling,

then you're not looking!


> only keep hearing claims.

interesting how you're happy to expound theories about eliminating metal
fatigue in a material with no endurance limit, contrary to established
fact, yet here, where mechanical principles are much more basic, you
seem to have comprehension problems.


>
>> An amazing amount of cable housing seating occurring during the
>> first half mile of the 2nd ride that for some reason just didn't
>> happen during the 3 miles of the 1st ride?
>
> Amazing story!

it's perfectly reasonable jobst - the only thing that's amazing is your
lack of desire [or ability] to think!

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> Tom Kunich wrote:
>
>>> I also considered using the shifter cable from an old Positron RD
>>> to see if that would reduce the slack enough to get decent
>>> performance out of the rear brake, as according to the yachting
>>> world a solid wire is less springy than a multi strand wire(for a
>>> given diameter).
>
>> The problem isn't the inner wire but the outer casing I believe.
>
> As the following web site shows, this has been a bugaboo for a long
> time, so much so that people designed cable housings to prevent this
> kind of "cable stretch" in spite of it not occurring. The sponge in
> brakes is elastic and most elastic elements are bending elements and
> brake pads. Thecaliper is a bending element and the pads are
> elastomers and have toe-in.
>
> http://www.gravity-slaves.co.uk/main/?p=show_article&article_ID=127
>

oh, how the worm turns. only a few days ago, all brake elasticity was
attributable only to "elastomeric brake pads"!

10 points for audacity.
0 for consistency.

now, let's clear up this ridiculous inconsistency on "stretch". you use
that word interchangeably between the regimes of elasticity and
plasticity, flip-flopping depending on whichever suits your particular
argument as the thread unfurls.

coming from an "engineer" so fond of lecturing on the use of linguistic
precision, such sloppiness would normally be one of two things:

1. poor grasp of the concepts.
2. deliberate obfuscation to allow the great jobst brandt to bully
anyone who dare encroach on "his territory".

given the nature of proceedings so far however, we might actually be
observing both!

[Michael Press]

In article <FICdnSkWHuRvYK_VnZ2dnUVZ_gudnZ2d@earthlink.com>,
"Tom Kunich" <cyclintom@yahoo. com> wrote:

> <jobst.brandt@stanfordalumni.org> wrote in message
> news:4832d837$0$34541$742ec2ed@news.sonic.net...
> > Tom Kunich wrote:
> >> No Jobst, I actually MEASURED the distances from the fulcrum and it
> >> was about 2.5:1. I say about because of the adjustments for the shoe
> >> placement.
> >
> > I didn't notice that anyone mentions dimensions in this thread or that
> > measurements were made and how. I just fine the language used for
> > brakes is misleading and asked what is linear and what the MA is in
> > the brake mentioned. Just because the cable moves farther doesn't
> > prove that this difference is canceled by the caliper leverage.
>
> After all these years you should be more than prepared for the inaccurate
> language used by most people when talking about mechanical things.
>
> I used a metric tape measure to measure the distance to the brake shoe
> center and to the cable attachment point. The leverage of the (Shimano XT)
> unit was approximately 2.5:1. We don't need precision here.

We do need accuracy of language, and accuracy is what you
are talking about here where you misuse the word `precision.'
They are not synonyms. Precision measures the repeatability
of a measuring technique.

Accuracy in a clock is how closely it reads to the `real' time.
Precision of a clock is the variability of the intervals between ticks.

--
Michael Press

[jim beam]

jobst.brandt@stanfordalumni.org wrote:
> clare who? wrote:
>
>>>> I asked what the effective MA of the brake is from hand lever to
>>>> brake pad and what brake pad and what made it "linear".
>
> OK, how much more linear and how about a graph of had lever motion vs
> pad motion comparing the most common brakes.

ok, how about NOT having 1/sin theta affecting the mechanical advantage
of the straddle cable?????



>
>> What makes it linear?
>
>> The mechanical advantage does not change with either the position of
>> the brake handle, or the position of the pad. Moving the handle the
>> first 1/16" moves the pads the same distance as the last 1/16"
>> (within a VERY small variance - so small as to be inconsequential)
>> This is NOT true of a center-pull or a cantilever because the angle
>> of the pull changes in an "arc" both at the handle end and at the
>> "caliper" end. Worse yet, the non-linearity ADDS instead of
>> canceling. The dual pivot "linear pull" handles pull straight - as
>> does the "V" brake "caliper".
>
> Show how much this is on a graph.
>
>> Really quite a simple concept.
>
> Not simple at all. Just recall how long it took the concept of the
> Dual Pivot brake to be even partly understood and why two pivots.
>
> We aren't getting any closer to the answer of MA or linearity.
>

and you aren't getting any closer to you ever being able to pay any
freakin' attention to anything you didn't read before age 30. and
precious little of /that/ seems to have sunk in properly.

from: http://sheldonbrown.com/cantilever-geometry.html [thanks carl]

Yoke Angle Mechanical
(Degrees) Advantage
90° 1
80° 1.015
70° 1.063
60° 1.15
50° 1.31
40° 1.55
30° 2
20° 2.92
10° 5.76
5° 11.47
0° Infinity!

[Tom Kunich]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:r-udnWFZwNTkDq7VnZ2dnUVZ_q7inZ2d@speakeasy.net...
> jobst.brandt@stanfordalumni.org wrote:
>> For that reason, measuring
>> hand lever stroke and combined pad(s) stroke is the only unambiguous
>> measure of MA. The article by Sheldon is as vague as claims by brake
>> manufacturers.
>
> rubbish jobst. the math is clear and unambiguous.

Jim, because of your dislike of Jobst's style you're failing to understand
what he's saying. In truth he is correct that in order to get the same BRAKE
PAD TRAVEL you need to have the same overall ratios. There is a small
problem in that idea though - in order to make the brake lever forces
smaller, they set the system up to use SHORTER TRAVEL. The results of this
is that linear brakes have to have very straight wheels and the pads are set
much closer to the rims.

So in truth the linear braking system does use a higher MA but at the cost
of higher maintenance.

[Lou Holtman]

Marian wrote:
> So here I am riding on impossible dirt roads in the rain in Guangxi
> province and my brakes have just stopped working. At least at the
> beginning I was able to deal with this on some of the gentler
> downhills by doing a Fred Flintstone with my left foot while I was
> riding and later on I figured out that if I got up off the saddle and
> sat on the top tube pulling on the brake cable I could slow myself
> still farther but the brakes are just refusing to stop the bike.
>
> I've done a cursory inspection, cleaned them, tightened them, loosened
> them, tightened them, moved things, moved things back, spun the wheel
> up, pulled on the brake lever and all I get is a scthscthscth noise
> which gradually results in the wheel slowing down but not really
> stopping. And this when nothing is on the bike.
>
> They worked fine yesterday.
>
> Heck, they worked fine this morning.
>
> It was just when the rain and the mud started getting bad (along about
> the same time that the really bad downhills stopped but around the
> same time that the road condition deteriorated further) that this
> happened. The levers still squeeze but the wheels don't stop
> anymore. The person who was riding with me on a mountain bike (who
> has since gone home) had the same kind of V-brakes as my front brake
> (plain jane no name Shimano) and I've got Deore for my rear brake with
> original brake pads that are nowhere near the wear line (only about
> 700km old).
>
> What happened?
>
> What can I do about it?
>
> -M


Change the pads, that is all you can try. Cheap brakes come with ****ty
pads. In this conditions disk brakes come in handy by the way.

Lou

[catzz66]

Marian wrote:
>
>
> What can I do about it?
>
> -M

I would suspect the pads, like Lou said. I am more prone to picking up
foreign matter in my pads when it is wet and I am having to ride through
mucky roads. My pads are pretty good. I am still on the factory ones,
but it is not a big deal to change them out. Look at the rims. If you
have been riding with junk in the pads, it is pretty easy to score and
scratch your rims.

Sometimes for me, it is just grit and I can flush it out with the garden
hose. I have also been known to borrow a little pond water if I am far
away from home and wash everything down in the middle of a ride.

[M-gineering]

Marian wrote:
> So here I am riding on impossible dirt roads in the rain in Guangxi
> province and my brakes have just stopped working. At least at the
> beginning I was able to deal with this on some of the gentler
> downhills by doing a Fred Flintstone with my left foot while I was
> riding and later on I figured out that if I got up off the saddle and
> sat on the top tube pulling on the brake cable I could slow myself
> still farther but the brakes are just refusing to stop the bike.
>
> I've done a cursory inspection, cleaned them, tightened them, loosened
> them, tightened them, moved things, moved things back, spun the wheel
> up, pulled on the brake lever and all I get is a scthscthscth noise
> which gradually results in the wheel slowing down but not really
> stopping. And this when nothing is on the bike.
>
> They worked fine yesterday.
>
> Heck, they worked fine this morning.
>
> It was just when the rain and the mud started getting bad (along about
> the same time that the really bad downhills stopped but around the
> same time that the road condition deteriorated further) that this
> happened. The levers still squeeze but the wheels don't stop
> anymore. The person who was riding with me on a mountain bike (who
> has since gone home) had the same kind of V-brakes as my front brake
> (plain jane no name Shimano) and I've got Deore for my rear brake with
> original brake pads that are nowhere near the wear line (only about
> 700km old).
>
> What happened?
>
> What can I do about it?
>
> -M
Are the brakes setup so that the noodle bottoms out against the
clampbolt on the V-s? Check that there is sufficient space, if not
change the washers on the brakeblock holder around

--
/Marten

info(apestaartje)m-gineering(punt)nl

[Lou Holtman]

Marian wrote:
> So here I am riding on impossible dirt roads in the rain in Guangxi
> province and my brakes have just stopped working. At least at the
> beginning I was able to deal with this on some of the gentler
> downhills by doing a Fred Flintstone with my left foot while I was
> riding and later on I figured out that if I got up off the saddle and
> sat on the top tube pulling on the brake cable I could slow myself
> still farther but the brakes are just refusing to stop the bike.
>
> I've done a cursory inspection, cleaned them, tightened them, loosened
> them, tightened them, moved things, moved things back, spun the wheel
> up, pulled on the brake lever and all I get is a scthscthscth noise
> which gradually results in the wheel slowing down but not really
> stopping. And this when nothing is on the bike.
>
> They worked fine yesterday.
>
> Heck, they worked fine this morning.
>
> It was just when the rain and the mud started getting bad (along about
> the same time that the really bad downhills stopped but around the
> same time that the road condition deteriorated further) that this
> happened. The levers still squeeze but the wheels don't stop
> anymore. The person who was riding with me on a mountain bike (who
> has since gone home) had the same kind of V-brakes as my front brake
> (plain jane no name Shimano) and I've got Deore for my rear brake with
> original brake pads that are nowhere near the wear line (only about
> 700km old).
>
> What happened?
>
> What can I do about it?
>
> -M


Change the pads, that is all you can try. Cheap brakes come with ****ty
pads. In this conditions disk brakes come in handy by the way.

Lou

[catzz66]

Marian wrote:
>
>
> What can I do about it?
>
> -M

I would suspect the pads, like Lou said. I am more prone to picking up
foreign matter in my pads when it is wet and I am having to ride through
mucky roads. My pads are pretty good. I am still on the factory ones,
but it is not a big deal to change them out. Look at the rims. If you
have been riding with junk in the pads, it is pretty easy to score and
scratch your rims.

Sometimes for me, it is just grit and I can flush it out with the garden
hose. I have also been known to borrow a little pond water if I am far
away from home and wash everything down in the middle of a ride.

[M-gineering]

Marian wrote:
> So here I am riding on impossible dirt roads in the rain in Guangxi
> province and my brakes have just stopped working. At least at the
> beginning I was able to deal with this on some of the gentler
> downhills by doing a Fred Flintstone with my left foot while I was
> riding and later on I figured out that if I got up off the saddle and
> sat on the top tube pulling on the brake cable I could slow myself
> still farther but the brakes are just refusing to stop the bike.
>
> I've done a cursory inspection, cleaned them, tightened them, loosened
> them, tightened them, moved things, moved things back, spun the wheel
> up, pulled on the brake lever and all I get is a scthscthscth noise
> which gradually results in the wheel slowing down but not really
> stopping. And this when nothing is on the bike.
>
> They worked fine yesterday.
>
> Heck, they worked fine this morning.
>
> It was just when the rain and the mud started getting bad (along about
> the same time that the really bad downhills stopped but around the
> same time that the road condition deteriorated further) that this
> happened. The levers still squeeze but the wheels don't stop
> anymore. The person who was riding with me on a mountain bike (who
> has since gone home) had the same kind of V-brakes as my front brake
> (plain jane no name Shimano) and I've got Deore for my rear brake with
> original brake pads that are nowhere near the wear line (only about
> 700km old).
>
> What happened?
>
> What can I do about it?
>
> -M
Are the brakes setup so that the noodle bottoms out against the
clampbolt on the V-s? Check that there is sufficient space, if not
change the washers on the brakeblock holder around

--
/Marten

info(apestaartje)m-gineering(punt)nl

[Ecnerwal]

In article
<1c1f688d-c57e-448c-b4e4-40c8fd953b3d@f24g2000prh.googlegroups.com>,
Marian <marian.rosenberg@gmail.com> wrote:

> original brake pads that are nowhere near the wear line (only about
> 700km old).
>
> What happened?

Perhaps one of the mud puddles was a puddle of oil, or with an oil film.
This would coat the rims and pads, and screw up braking royally.

> What can I do about it?

Scrub the wheel rims (with soap and water), scrub the pads, if still no
better, replace the pads.

Others have had other good suggestions to check for, which you'll see if
you take stuff apart to scrub it down - pebbles lodged in things, pads
whacked out of adjustment, etc.

--
Cats, coffee, chocolate...vices to live by

[Lou Holtman]

Lou Holtman wrote:
> Marian wrote:
>> So here I am riding on impossible dirt roads in the rain in Guangxi
>> province and my brakes have just stopped working. At least at the
>> beginning I was able to deal with this on some of the gentler
>> downhills by doing a Fred Flintstone with my left foot while I was
>> riding and later on I figured out that if I got up off the saddle and
>> sat on the top tube pulling on the brake cable I could slow myself
>> still farther but the brakes are just refusing to stop the bike.
>>
>> I've done a cursory inspection, cleaned them, tightened them, loosened
>> them, tightened them, moved things, moved things back, spun the wheel
>> up, pulled on the brake lever and all I get is a scthscthscth noise
>> which gradually results in the wheel slowing down but not really
>> stopping. And this when nothing is on the bike.
>>
>> They worked fine yesterday.
>>
>> Heck, they worked fine this morning.
>>
>> It was just when the rain and the mud started getting bad (along about
>> the same time that the really bad downhills stopped but around the
>> same time that the road condition deteriorated further) that this
>> happened. The levers still squeeze but the wheels don't stop
>> anymore. The person who was riding with me on a mountain bike (who
>> has since gone home) had the same kind of V-brakes as my front brake
>> (plain jane no name Shimano) and I've got Deore for my rear brake with
>> original brake pads that are nowhere near the wear line (only about
>> 700km old).
>>
>> What happened?
>>
>> What can I do about it?
>>
>> -M
>
>
> Change the pads, that is all you can try. Cheap brakes come with ****ty
> pads. In this conditions disk brakes come in handy by the way.
>
> Lou


O, and clean the rims. Maybe they are contaminated with some oily/greasy
stuff.

Lou

[Lou Holtman]

Lou Holtman wrote:
> Marian wrote:
>> So here I am riding on impossible dirt roads in the rain in Guangxi
>> province and my brakes have just stopped working. At least at the
>> beginning I was able to deal with this on some of the gentler
>> downhills by doing a Fred Flintstone with my left foot while I was
>> riding and later on I figured out that if I got up off the saddle and
>> sat on the top tube pulling on the brake cable I could slow myself
>> still farther but the brakes are just refusing to stop the bike.
>>
>> I've done a cursory inspection, cleaned them, tightened them, loosened
>> them, tightened them, moved things, moved things back, spun the wheel
>> up, pulled on the brake lever and all I get is a scthscthscth noise
>> which gradually results in the wheel slowing down but not really
>> stopping. And this when nothing is on the bike.
>>
>> They worked fine yesterday.
>>
>> Heck, they worked fine this morning.
>>
>> It was just when the rain and the mud started getting bad (along about
>> the same time that the really bad downhills stopped but around the
>> same time that the road condition deteriorated further) that this
>> happened. The levers still squeeze but the wheels don't stop
>> anymore. The person who was riding with me on a mountain bike (who
>> has since gone home) had the same kind of V-brakes as my front brake
>> (plain jane no name Shimano) and I've got Deore for my rear brake with
>> original brake pads that are nowhere near the wear line (only about
>> 700km old).
>>
>> What happened?
>>
>> What can I do about it?
>>
>> -M
>
>
> Change the pads, that is all you can try. Cheap brakes come with ****ty
> pads. In this conditions disk brakes come in handy by the way.
>
> Lou


O, and clean the rims. Maybe they are contaminated with some oily/greasy
stuff.

Lou

[Marian]

On May 18, 7:09*pm, catzz66 <catz...@threeletterservice.com> wrote:
> Marian wrote:
>
> > What can I do about it?
>
> > -M
>
> I would suspect the pads, like Lou said. *I am more prone to picking up
> foreign matter in my pads when it is wet and I am having to ride through
> mucky roads. *My pads are pretty good. *I am still on the factory ones,
> but it is not a big deal to change them out. *Look at the rims. *If you
> have been riding with junk in the pads, it is pretty easy to score and
> scratch your rims.

Deore XT brakes on the back, something nameless and Shimano on the
front.

Very scratched up rims, and pretty scratched up pads too.

Changed out the brake pads on the back (which was the worst) and it's
better but still not the stopping power I had before. New brake pads
are something nameless and Chinese.

The first day's brake failure was on moderately bad roads. I washed,
readjusted, tweaked, changed spacers, got minimally satisfactory
braking power back, and went wading through mud puddles up to my
bottom bracket until the brakes failed again (at which point I gave up
and took a bus back to the closest town with a bike shop).

> Sometimes for me, it is just grit and I can flush it out with the garden
> hose. *I have also been known to borrow a little pond water if I am far
> away from home and wash everything down in the middle of a ride.

[Tom Kunich]

"M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
news:g0p7uf$afe$1@localhost.localdomain...
> Are the brakes setup so that the noodle bottoms out against the clampbolt
> on the V-s? Check that there is sufficient space, if not change the
> washers on the brakeblock holder around

I'm certainly glad that I'm not practicing engineering in the Netherlands
where they apparently speak some sort of foreign language...... :-)

[Lou Holtman]

Tom Kunich wrote:
> "M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
> news:g0p7uf$afe$1@localhost.localdomain...
>> Are the brakes setup so that the noodle bottoms out against the
>> clampbolt on the V-s? Check that there is sufficient space, if not
>> change the washers on the brakeblock holder around
>
> I'm certainly glad that I'm not practicing engineering in the
> Netherlands where they apparently speak some sort of foreign
> language...... :-)

How is your Dutch Tom? Flapdrol..

Lou

[Andre Jute]

On May 18, 2:40*pm, "Tom Kunich" <cyclintom@yahoo. com> wrote:
> "M-gineering" <ikmotgeens...@m-gineering.nl> wrote in message
>
> news:g0p7uf$afe$1@localhost.localdomain...
>
> > Are the brakes setup so that the noodle bottoms out against the clampbolt
> > on the V-s? Check that there is sufficient space, if not change the
> > washers on the brakeblock holder around
>
> I'm certainly glad that I'm not practicing engineering in the Netherlands
> where they apparently speak some sort of foreign language...... :-)

You must be one of those well-travelled Americans we hear about, Tom,
who have been all the way to Vegas. FYI:

1. In The Netherlands (note which words are capitalized) they speak
Dutch. It is their native language.

2. In The Netherlands English is a foreign language.

3. All the same, the Dutch speak better English too than most
Americans. (Hell, the Dutch and the Germans also speak better English
than most English people with impenetrable regional accents.)

4. The Dutch, who're pretty outspoken, would never dream of making fun
of you, dear Tom, because you can't understand plain English.

***

5. More generally, the difference between anglophones and cultured
people is that cultured people speak more than one language and
anglophones think they speak French when they raise their voices in
English (1).

6. Engineers, being generally much less sensitive to social nuance and
the finer feelings than people, are substantially more likely to be
monophonic than people.

Those are the facts. My opinion doesn't necessarily coincide.

Andre Jute
http://members.lycos.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html

(1) According to one of my literary protege, herself one of those
ultra-rare creatures, a linguistically gifted and sensitive engineer,
the French do not speak English as a homage to a world language but to
stop the British mangling French so. Sounds about right me.

[A Muzi]

> "M-gineering" <ikmotgeenspam@m-gineering.nl> wrote in message
> news:g0p7uf$afe$1@localhost.localdomain...
>> Are the brakes setup so that the noodle bottoms out against the
>> clampbolt on the V-s? Check that there is sufficient space, if not
>> change the washers on the brakeblock holder around

Tom Kunich wrote:
> I'm certainly glad that I'm not practicing engineering in the
> Netherlands where they apparently speak some sort of foreign
> language...... :-)

huh.
That seemed quite clear (and sorta good advice BTW) to me. It's both a
real and a common problem.

I already suggested cantilevers rather than liner brakes to her weeks
ago but those weren't readily available to her. Linear ("V") brakes are
more prone to crud embedding and have rapid pad and rim wear. That goes
double in dirt and rain.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[Nate Nagel]

Andre Jute wrote:
> On May 18, 2:40 pm, "Tom Kunich" <cyclintom@yahoo. com> wrote:
>
>>"M-gineering" <ikmotgeens...@m-gineering.nl> wrote in message
>>
>>news:g0p7uf$afe$1@localhost.localdomain...
>>
>>
>>>Are the brakes setup so that the noodle bottoms out against the clampbolt
>>>on the V-s? Check that there is sufficient space, if not change the
>>>washers on the brakeblock holder around
>>
>>I'm certainly glad that I'm not practicing engineering in the Netherlands
>>where they apparently speak some sort of foreign language...... :-)
>
>
> You must be one of those well-travelled Americans we hear about, Tom,
> who have been all the way to Vegas. FYI:
>
> 1. In The Netherlands (note which words are capitalized) they speak
> Dutch. It is their native language.
>
> 2. In The Netherlands English is a foreign language.
>
> 3. All the same, the Dutch speak better English too than most
> Americans. (Hell, the Dutch and the Germans also speak better English
> than most English people with impenetrable regional accents.)
>
> 4. The Dutch, who're pretty outspoken, would never dream of making fun
> of you, dear Tom, because you can't understand plain English.
>
> ***
>
> 5. More generally, the difference between anglophones and cultured
> people is that cultured people speak more than one language and
> anglophones think they speak French when they raise their voices in
> English (1).
>
> 6. Engineers, being generally much less sensitive to social nuance and
> the finer feelings than people, are substantially more likely to be
> monophonic than people.
>
> Those are the facts. My opinion doesn't necessarily coincide.
>
> Andre Jute
> http://members.lycos.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html
>
> (1) According to one of my literary protege, herself one of those
> ultra-rare creatures, a linguistically gifted and sensitive engineer,
> the French do not speak English as a homage to a world language but to
> stop the British mangling French so. Sounds about right me.

I realize this is probably just meant as a mild needle, but the truth is
that the YooEss is a very large country and therefore many people don't
ever encounter non-English speaking people throughout their entire
lives. That's changing somewhat of late; I've started to think that
learning Spanish might not he a completely bad idea, but it's not one of
those things that you can just go out and do in a weekend.

nate

(and you really, really don't want to hear me speaking French. You just
don't.)

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[Martin Borsje]

Hear, hear!

;-)

[Marian]

On May 19, 2:37*am, A Muzi <a...@yellowjersey.org> wrote:
> > "M-gineering" <ikmotgeens...@m-gineering.nl> wrote in message
> >news:g0p7uf$afe$1@localhost.localdomain...
> >> Are the brakes setup so that the noodle bottoms out against the
> >> clampbolt on the V-s? Check that there is sufficient space, if not
> >> change the washers on the brakeblock holder around
> Tom Kunich wrote:
> > I'm certainly glad that I'm not practicing engineering in the
> > Netherlands where they apparently speak some sort of foreign
> > language...... :-)
>
> huh.
> That seemed quite clear (and sorta good advice BTW) to me. It's both a
> real and a common problem.
>
> I already suggested cantilevers rather than liner brakes to her weeks
> ago but those weren't readily available to her. Linear ("V") brakes are
> more prone to crud embedding and have rapid pad and rim wear. That goes
> double in dirt and rain.

If it's any consolation, my mechanic agrees with you. But he couldn't
get cantilevers in before I was due to leave.

I'm taking a very pragmatic approach to choosing roads on this bike
tour.

1) Ask everyone around me the best route from here to there.
2) Take the road everyone tells me to avoid using.

Even if I was walking most of the time I wasn't going that much slower
than the four wheel drive power bus with the tires only slightly
shorter than me. And the mud rarely came up above my calves. It was
however the sucking kind where I sometimes had to wiggle my toes to
keep my shoes on when I pulled out for the next step.

-M

[jim beam]

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:r-udnWFZwNTkDq7VnZ2dnUVZ_q7inZ2d@speakeasy.net...
>> jobst.brandt@stanfordalumni.org wrote:
>>> For that reason, measuring
>>> hand lever stroke and combined pad(s) stroke is the only unambiguous
>>> measure of MA. The article by Sheldon is as vague as claims by brake
>>> manufacturers.
>>
>> rubbish jobst. the math is clear and unambiguous.
>
> Jim, because of your dislike of Jobst's style you're failing to
> understand what he's saying. In truth he is correct that in order to get
> the same BRAKE PAD TRAVEL you need to have the same overall ratios.
> There is a small problem in that idea though - in order to make the
> brake lever forces smaller, they set the system up to use SHORTER
> TRAVEL. The results of this is that linear brakes have to have very
> straight wheels and the pads are set much closer to the rims.

there's two things - the leverage ratios you refer to for "v" and
caliper brakes, and the leverage ratios for cantilevers. the latter is
variable, as a function of straddle cable angle.


>
> So in truth the linear braking system does use a higher MA but at the
> cost of higher maintenance.
>

higher maintenance???

[A Muzi]

>>> Andrew Muzi wrote:
>>>> I already suggested cantilevers rather than liner brakes to her
>>>> weeks ago but those weren't readily available to her. Linear
>>>> ("V") brakes are more prone to crud embedding and have rapid pad
>>>> and rim wear. That goes double in dirt and rain.

>>> Are you blaming the pads or the mechanics of the linear brake?

>>> My current touring/commuting bike has cantilever brakes that use
>>> "V" type pad (lots of surface area but thin.) For what it's worth,
>>> I do find the pads wear quickly. Given that I ride in rain, snow,
>>> salt, etc, that's to be expected, and at $4 a pair, I'm not too
>>> broken up about it. What I really love is that I can change them
>>> out without having to reset the brakes, something I never liked
>>> about traditional cantilever brakes with smooth stud shoes.

> Andrew Muzi wrote:
>> Although Kool Stop pads are better than OEM (also not readily
>> available to Marian), linear systems promote rapid rim wear and seem
>> to be more prone to crud in the pads - whether it jams in faster or
>> just scrapes rim chunks into the pad faster I can't say.

jobst.brandt@stanfordalumni.org wrote:
> Having had many years to research brakes, starting with Universal,
> pre-Campagnolo brakes, Weinmann, and various centerpull calipers, I
> searched for several effects: 1) Embedded grit in pads, 2) Hand lever
> braking force required and 3) brake pad wear rate. In that pursuit I
> also measured mechanical advantage of various brakes and discovered
> that contrary to he bicycling press, all calipers had a 1:1 ratio and
> hand levers had 4:1. That is, the mechanical advantage was the same
> for all brakes (Including Campagnolo when they took over the high
> quality end of the business and having an excellent QR.
>
> What I found was that Kool-Stop Salmon pads were the best, Campagnolo
> a distant second, and Mafac, horrible in that they always chewed up
> rims. Universal didn't come off well either. The most striking
> feature of Kool-Stop pads was that even when riding through wet dirt
> and picking up road mud and grit, the pads would clear themselves once
> back on pavement by merely pumping the brake hard.
>
> Not being one to worry about fashion and having a line of
> practicality, I chose the Continental model because, unlike inserts
> (typically in Campagnolo and Universal brakes) these pads could not be
> accidentally knocked out of the pad holder when inserting a wheel,
> something I observed happening a few times to the surprise of a rider
> after a wheel change.
>
> High pitch squeal is mainly caused by contamination on the braking
> surface, mainly humidity, but also from soft drink splash or even
> urine from roadside relief while standing astride the bicycle. Squeal
> can be cleared up by heavy braking on a steep descent that gets rims
> hot. It is not a matter of pad toe-in as is often claimed.
>
> Just the same, toe-in occurs naturally because when braking hard
> caliper arms bend forward in a way that makes the rear of the pad wear
> faster than the forward end. I suppose someone noticed that well worn
> pads seldom squealed AND that they had toe-in, which led to brutal
> deformation of brake calipers. If this were a manually added feature,
> then it should be added by running a rasp lengthwise across the brake
> pad, not by bending brake calipers.
> http://www.koolstop.com/brakes/index.php

That's all generally helpful but the specific bike here has linear ("V")
brakes, which not only have a ratio with greater cable travel and
greater pressure at the rim for a given effort at the lever, but are
notorious for chewing rims and pads.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[travis.harry@gmail.com]

On May 18, 9:16 pm, jobst.bra...@stanfordalumni.org wrote:
> Andrew Muzi wrote:
> >>> I already suggested cantilevers rather than liner brakes to her
> >>> weeks ago but those weren't readily available to her. Linear
> >>> ("V") brakes are more prone to crud embedding and have rapid pad
> >>> and rim wear. That goes double in dirt and rain.
> >> Are you blaming the pads or the mechanics of the linear brake?
> >> My current touring/commuting bike has cantilever brakes that use
> >> "V" type pad (lots of surface area but thin.) For what it's worth,
> >> I do find the pads wear quickly. Given that I ride in rain, snow,
> >> salt, etc, that's to be expected, and at $4 a pair, I'm not too
> >> broken up about it. What I really love is that I can change them
> >> out without having to reset the brakes, something I never liked
> >> about traditional cantilever brakes with smooth stud shoes.
> > Although Kool Stop pads are better than OEM (also not readily
> > available to Marian), linear systems promote rapid rim wear and seem
> > to be more prone to crud in the pads - whether it jams in faster or
> > just scrapes rim chunks into the pad faster I can't say.
>
> Having had many years to research brakes, starting with Universal,
> pre-Campagnolo brakes, Weinmann, and various centerpull calipers, I
> searched for several effects: 1) Embedded grit in pads, 2) Hand lever
> braking force required and 3) brake pad wear rate. In that pursuit I
> also measured mechanical advantage of various brakes and discovered
> that contrary to he bicycling press, all calipers had a 1:1 ratio and
> hand levers had 4:1. That is, the mechanical advantage was the same
> for all brakes (Including Campagnolo when they took over the high
> quality end of the business and having an excellent QR.
>
> What I found was that Kool-Stop Salmon pads were the best, Campagnolo
> a distant second, and Mafac, horrible in that they always chewed up
> rims. Universal didn't come off well either. The most striking
> feature of Kool-Stop pads was that even when riding through wet dirt
> and picking up road mud and grit, the pads would clear themselves once
> back on pavement by merely pumping the brake hard.
>
> Not being one to worry about fashion and having a line of
> practicality, I chose the Continental model because, unlike inserts
> (typically in Campagnolo and Universal brakes) these pads could not be
> accidentally knocked out of the pad holder when inserting a wheel,
> something I observed happening a few times to the surprise of a rider
> after a wheel change.
>
> High pitch squeal is mainly caused by contamination on the braking
> surface, mainly humidity, but also from soft drink splash or even
> urine from roadside relief while standing astride the bicycle. Squeal
> can be cleared up by heavy braking on a steep descent that gets rims
> hot. It is not a matter of pad toe-in as is often claimed.
>
> Just the same, toe-in occurs naturally because when braking hard
> caliper arms bend forward in a way that makes the rear of the pad wear
> faster than the forward end. I suppose someone noticed that well worn
> pads seldom squealed AND that they had toe-in, which led to brutal
> deformation of brake calipers. If this were a manually added feature,
> then it should be added by running a rasp lengthwise across the brake
> pad, not by bending brake calipers.
>
> http://www.koolstop.com/brakes/index.php
> --
> Jobst Brandt

One can find online--trust me--a more recent review of perhaps 8
different replacement brake pads done by a British bicycling mag. I
cannot recall the testing methodology. But the design included testing
wet and dry separately and reporting braking distance as well as
remarks on aluminum extracted from the rims by the different pads.. I
found troubling the substantial negative rank order correlation
between wet and dry performance. Not perfectly negative, but high
enough that you would not pick out one pad as a reasonable compromise,
sacrificing just a little performance in one condition to achieve high
performance in the other.

[jobst.brandt@stanfordalumni.org]

Andrew Muzi wrote:

> That's all generally helpful but the specific bike here has linear
> ("V") brakes, which not only have a ratio with greater cable travel
> and greater pressure at the rim for a given effort at the lever, but
> are notorious for chewing rims and pads.

Maybe you can tell me what is "linear" about these brakes and what the
MA (mechanical advantage) is. Appearances can deceive. It was once
believed that centerpull brakes had twice the MA of sidepull calipers
based on the length of caliper input levers on which the straddle
cable acts. This ignored that there are two of these, which divides
that apparent MA in two.

Other than these considerations, more pad force does not affect
whether they develop grit or not.

Jobst Brandt

[A Muzi]

-snip brakes-
Marian wrote:
> Even if I was walking most of the time I wasn't going that much slower
> than the four wheel drive power bus with the tires only slightly
> shorter than me. And the mud rarely came up above my calves. It was
> however the sucking kind where I sometimes had to wiggle my toes to
> keep my shoes on when I pulled out for the next step.

It's not just sticky. As the plumbers say, "It's alive!"
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[Tom Kunich]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:rd6dnYoPP5mIs6vVnZ2dnUVZ_gednZ2d@speakeasy.ne t...
>
> higher maintenance???

You have to keep your rims perfectly straight and the brakes in good
adjustment all the time.

[Tom Kunich]

"dabac" <dabac.39vf3z@no-mx.forums.cyclingforums.com> wrote in message
news:dabac.39vf3z@no-mx.forums.cyclingforums.com...
>
> I also considered using the shifter cable from an old Positron RD to
> see if that would reduce the slack enough to get decent performance out
> of the rear brake, as according to the yachting world a solid wire is
> less springy than a multi strand wire(for a given diameter).

The problem isn't the inner wire but the outer casing I believe.

[A Muzi]

> Andrew Muzi wrote:
>> That's all generally helpful but the specific bike here has linear
>> ("V") brakes, which not only have a ratio with greater cable travel
>> and greater pressure at the rim for a given effort at the lever, but
>> are notorious for chewing rims and pads.

jobst.brandt@stanfordalumni.org wrote:
> Maybe you can tell me what is "linear" about these brakes and what the
> MA (mechanical advantage) is. Appearances can deceive. It was once
> believed that centerpull brakes had twice the MA of sidepull calipers
> based on the length of caliper input levers on which the straddle
> cable acts. This ignored that there are two of these, which divides
> that apparent MA in two.
>
> Other than these considerations, more pad force does not affect
> whether they develop grit or not.

"Linear" a.k.a. "Direct Pull" a.k.a. "V" type brakes really are
different from all other cable actuated bicycle brakes. Here are the
lurid details, provided by Sheldon from beyond the grave:

http://www.sheldonbrown.com/canti-direct.html
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

[Tim McNamara]

In article
<a90e4292-e84e-47b0-a0c3-8aa5c0c944a1@y38g2000hsy.googlegroups.com>,
"travis.harry@gmail.com" <travis.harry@gmail.com> wrote:

> One can find online--trust me--a more recent review of perhaps 8
> different replacement brake pads done by a British bicycling mag. I
> cannot recall the testing methodology. But the design included
> testing wet and dry separately and reporting braking distance as well
> as remarks on aluminum extracted from the rims by the different
> pads.. I found troubling the substantial negative rank order
> correlation between wet and dry performance. Not perfectly negative,
> but high enough that you would not pick out one pad as a reasonable
> compromise, sacrificing just a little performance in one condition to
> achieve high performance in the other.

Years ago, VeloNews compared a variety of brake pads using the old
Schwinn brake testing rig (basically a flywheel with a rim attached,
mounted in a fork). Wet and dry performance was tested. The Kool Stop
salmon material came out the best in both categories, as I recall.
VeloNews used to have this report posted on their Web site. Maybe
someone can ferret it out again.

[Peter Cole]

travis.harry@gmail.com wrote:

> One can find online--trust me--a more recent review of perhaps 8
> different replacement brake pads done by a British bicycling mag. I
> cannot recall the testing methodology. But the design included testing
> wet and dry separately and reporting braking distance as well as
> remarks on aluminum extracted from the rims by the different pads.. I
> found troubling the substantial negative rank order correlation
> between wet and dry performance. Not perfectly negative, but high
> enough that you would not pick out one pad as a reasonable compromise,
> sacrificing just a little performance in one condition to achieve high
> performance in the other.

There's this:

http://www.bicyclesource.com/testing_brake_pads

Not really very much difference, except for some in the wet test. I'm
suspicious that those use a more abrasive compound.

and this:

http://www.mtbr.com/reviews/brake_pad/index_bynumreviews.shtml

I've never found stopping power to be a concern. The only thing that is
an issue is rim wear.

[jobst.brandt@stanfordalumni.org]

Travis Harry wrote:

>>>>> I already suggested cantilevers rather than liner brakes to her
>>>>> weeks ago but those weren't readily available to her. Linear
>>>>> ("V") brakes are more prone to crud embedding and have rapid pad
>>>>> and rim wear. That goes double in dirt and rain.

>>>> Are you blaming the pads or the mechanics of the linear brake?
>>>> My current touring/commuting bike has cantilever brakes that use
>>>> "V" type pad (lots of surface area but thin.) For what it's
>>>> worth, I do find the pads wear quickly. Given that I ride in
>>>> rain, snow, salt, etc, that's to be expected, and at $4 a pair,
>>>> I'm not too broken up about it. What I really love is that I can
>>>> change them out without having to reset the brakes, something I
>>>> never liked about traditional cantilever brakes with smooth stud
>>>> shoes.

>>> Although Kool Stop pads are better than OEM (also not readily
>>> available to Marian), linear systems promote rapid rim wear and
>>> seem to be more prone to crud in the pads - whether it jams in
>>> faster or just scrapes rim chunks into the pad faster I can't say.

>> Having had many years to research brakes, starting with Universal,
>> pre-Campagnolo brakes, Weinmann, and various centerpull calipers, I
>> searched for several effects: 1) Embedded grit in pads, 2) Hand
>> lever braking force required and 3) brake pad wear rate. In that
>> pursuit I also measured mechanical advantage of various brakes and
>> discovered that contrary to he bicycling press, all calipers had a
>> 1:1 ratio and hand levers had 4:1. That is, the mechanical
>> advantage was the same for all brakes (Including Campagnolo when
>> they took over the high quality end of the business and having an
>> excellent QR.

>> What I found was that Kool-Stop Salmon pads were the best,
>> Campagnolo a distant second, and Mafac, horrible in that they
>> always chewed up rims. Universal didn't come off well either. The
>> most striking feature of Kool-Stop pads was that even when riding
>> through wet dirt and picking up road mud and grit, the pads would
>> clear themselves once back on pavement by merely pumping the brake
>> hard.

>> Not being one to worry about fashion and having a line of
>> practicality, I chose the Continental model because, unlike inserts
>> (typically in Campagnolo and Universal brakes) these pads could not
>> be accidentally knocked out of the pad holder when inserting a
>> wheel, something I observed happening a few times to the surprise
>> of a rider after a wheel change.

>> High pitch squeal is mainly caused by contamination on the braking
>> surface, mainly humidity, but also from soft drink splash or even
>> urine from roadside relief while standing astride the bicycle.
>> Squeal can be cleared up by heavy braking on a steep descent that
>> gets rims hot. It is not a matter of pad toe-in as is often
>> claimed.

>> Just the same, toe-in occurs naturally because when braking hard
>> caliper arms bend forward in a way that makes the rear of the pad
>> wear faster than the forward end. I suppose someone noticed that
>> well worn pads seldom squealed AND that they had toe-in, which led
>> to brutal deformation of brake calipers. If this were a manually
>> added feature, then it should be added by running a rasp lengthwise
>> across the brake pad, not by bending brake calipers.

http://www.koolstop.com/brakes/index.php

> One can find online --trust me-- a more recent review of perhaps 8
> different replacement brake pads done by a British bicycling mag. I
> cannot recall the testing methodology.

How about "testing method"? Methodology is the study of methods, just
as zoology is the study of animals.

> But the design included testing wet and dry separately and reporting
> braking distance as well as remarks on aluminum extracted from the
> rims by the different pads... I found troubling the substantial
> negative rank order correlation between wet and dry performance.
> Not perfectly negative, but high enough that you would not pick out
> one pad as a reasonable compromise, sacrificing just a little
> performance in one condition to achieve high performance in the
> other.

The most important criterion is grit accumulation IN the pad material,
something that cannot be washed off or even picked out with a sharp
tool. I explained the wet and dry performance here often in the past.
Pads that work when the rim is wet are also grit generators, because
it is the grit that is chewing up the rim that have traction on wet
rims.

As a test of this, try using rim brakes after riding through snow so
that the inner rim surface has a layer of snow. Practically no
braking will occur until all snow is melted and the rim friction
surface dries. This is a striking experiment about the effect of
water on braking. In contrast, when riding in moderate rain, rim
sidewalls are mostly dry once braking has warmed the rim. That is,
the rim does not have a contiguous coat of water.

Therefore, the testers, as often, don't understand the problem nor
tribology (study of friction and wear). In that vein, railroad
locomotives lose traction on wet rails because the critical last
monolayer of water molecules are not displaced by pressure (as with
brake pads) but require grit (locomotives have a large sand supply for
this). On double track railways in mountains, uphill tracks are white
with crushed sand debris while the downhill track is dark and rusty
from freight train iron brake shoes.

Jobst Brandt

[Marian]

On May 24, 8:43*am, A Muzi <a...@yellowjersey.org> wrote:
> -snip brakes-Marian wrote:
>
> * > Even if I was walking most of the time I wasn't going that much slower
>
> > than the four wheel drive power bus with the tires only slightly
> > shorter than me. *And the mud rarely came up above my calves. *It was
> > however the sucking kind where I sometimes had to wiggle my toes to
> > keep my shoes on when I pulled out for the next step.
>
> It's not just sticky. As the plumbers say, "It's alive!"

The next time someone tells me a road on my map is impassible by
bicycle, I might consider believing them.

Bearing in mind that 55 of yesterday's 68 km were dirt or pebble and I
ended up spending the night in a hotel (if that's not too grand a
word) that cost 10rmb (USD 1.43) per night.

Thus proving that the possibility of believing people when they say a
road is impassible by bicycle does not necessarily equal my not
deciding to take that road. It merely means that I'm not going to be
terribly surprised if I end up spending lots of time walking.

-M

[jobst.brandt@stanfordalumni.org]

Tom Kunich wrote:

>> I also considered using the shifter cable from an old Positron RD
>> to see if that would reduce the slack enough to get decent
>> performance out of the rear brake, as according to the yachting
>> world a solid wire is less springy than a multi strand wire(for a
>> given diameter).

No matter how closely you pack circular cross section strands,
they will have less cross sectional area than an equivalent diameter
solid wire, however, for the forces in brake cables, the stranded
cables do not stretch.

> The problem isn't the inner wire but the outer casing I believe.

Brake cable housing is, in essence, a stack of rings that when formed
into a curve as brake cables require, the central axis of the housing
elongates because the inner length is incompressible and the outer
length is free to open gaps between coils. If the housing has any
kinks, these will straighten and cause a spongy feeling when braking.
That my be where the "cable stretch

Because this well understood characteristic of "Bowden" cables makes
no difference to a force transmitting function, brake cables use it,
however, STI shifting relies on constant derailleur position and for
this reason Shimano made an STI shift cable housing that is not a
stack of rings (or even a close packed coil) and made a cable housing
that has long helix embedded wires. This housing is not designed to
transmit force, especially braking force, because it will burst and
collapse axially if used for brakes.

http://en.wikipedia.org/wiki/Bowden_cable

Jobst Brandt

[dabac]

Tom Kunich Wrote:
> "dabac" <dabac.39vf3z@no-mx.forums.cyclingforums.com> wrote in message
> news:dabac.39vf3z@no-mx.forums.cyclingforums.com...
> >
> > I also considered using the shifter cable from an old Positron RD to
> > see if that would reduce the slack enough to get decent performance
> out
> > of the rear brake, as according to the yachting world a solid wire
> is
> > less springy than a multi strand wire(for a given diameter).
>
> The problem isn't the inner wire but the outer casing I believe.

Well, every little helps if you're trying to get a borderline setup to
perform adequately...


--
dabac

[jobst.brandt@stanfordalumni.org]

Tom Kunich wrote:

>> I also considered using the shifter cable from an old Positron RD
>> to see if that would reduce the slack enough to get decent
>> performance out of the rear brake, as according to the yachting
>> world a solid wire is less springy than a multi strand wire(for a
>> given diameter).

> The problem isn't the inner wire but the outer casing I believe.

As the following web site shows, this has been a bugaboo for a long
time, so much so that people designed cable housings to prevent this
kind of "cable stretch", in spite of it not occurring. The sponge in
brakes is elastic, and the most elastic elements are bending elements
and brake pads. The caliper is a bending element and the pads are
elastomers and have toe-in.

http://www.gravity-slaves.co.uk/main/?p=show_article&article_ID=127

Jobst Brandt

[Tim McNamara]

In article <483a3c25$0$34542$742ec2ed@news.sonic.net>,
jobst.brandt@stanfordalumni.org wrote:

> Tom Kunich wrote:
>
> >> I also considered using the shifter cable from an old Positron RD
> >> to see if that would reduce the slack enough to get decent
> >> performance out of the rear brake, as according to the yachting
> >> world a solid wire is less springy than a multi strand wire(for a
> >> given diameter).
>
> No matter how closely you pack circular cross section strands, they
> will have less cross sectional area than an equivalent diameter solid
> wire, however, for the forces in brake cables, the stranded cables do
> not stretch.
>
> > The problem isn't the inner wire but the outer casing I believe.
>
> Brake cable housing is, in essence, a stack of rings that when formed
> into a curve as brake cables require, the central axis of the housing
> elongates because the inner length is incompressible and the outer
> length is free to open gaps between coils. If the housing has any
> kinks, these will straighten and cause a spongy feeling when braking.
> That my be where the "cable stretch

If the OP mentioned whether the bike has full-length cable housing or
uses split stops, I missed it. If the bike has full-length housing for
the rear brake cable, that might contribute to the problem.

[dabac]

jobst.brandt@stanfordalumni.org Wrote:
> Tom Kunich wrote:
>
> >> I also considered using the shifter cable from an old Positron RD
> >> to see if that would reduce the slack enough to get decent
> >> performance out of the rear brake, as according to the yachting
> >> world a solid wire is less springy than a multi strand wire(for a
> >> given diameter).
>
> No matter how closely you pack circular cross section strands,
> they will have less cross sectional area than an equivalent diameter
> solid wire, however, for the forces in brake cables, the stranded
> cables do not stretch.
>

I fear that this may bog down in another quagmire of semantics, but
cables do become longer. It may well be that each individual strand
doesn't elongate, but a cable as a whole can certainly become longer -
presumably by the voids in the cross section compressing when the cable
is under tension. Smaller voids, smaller diameter. And as the diameter
decreases the virtual center that the strands are wound around gets
smaller, thus allowing the cable to become longer even if the strands
themselves aren't stretching.
I once tried running some nice and thick cables originally intended for
scooters as brake cables on my bike and they gave a hopelessly mushy
feel that just didn't go away until I replaced them with some thinner
but more densely laid bicycle-specific cables.


--
dabac

[jobst.brandt@stanfordalumni.org]

someone wrote:

>>>> I also considered using the shifter cable from an old Positron RD
>>>> to see if that would reduce the slack enough to get decent
>>>> performance out of the rear brake, as according to the yachting
>>>> world a solid wire is less springy than a multi strand wire(for a
>>>> given diameter).

>> No matter how closely you pack circular cross section strands,
>> they will have less cross sectional area than an equivalent diameter
>> solid wire, however, for the forces in brake cables, the stranded
>> cables do not stretch.

> I fear that this may bog down in another quagmire of semantics, but
> cables do become longer. It may well be that each individual strand
> doesn't elongate, but a cable as a whole can certainly become longer
> - presumably by the voids in the cross section compressing when the
> cable is under tension. Smaller voids, smaller diameter. And as
> the diameter decreases the virtual center that the strands are wound
> around gets smaller, thus allowing the cable to become longer even
> if the strands themselves aren't stretching.

Brake cables available at bicycle supply houses have no voids and do
not stretch other than by the modulus of elasticity of steel of that
cross sectional area, and that is not palpable. Cable winding is a
well mastered technique, used by elevators, SF cable cars, ski lifts,
and myriad suspension bridges. They are close packed hexagonal cross
sections with no voids. They are wound in a way that when cutting a
bicycle control cable with diagonal cutters, the cable snaps back to
its round cross section because it is pre-loaded in constriction.

> I once tried running some nice and thick cables originally intended
> for scooters as brake cables on my bike and they gave a hopelessly
> mushy feel that just didn't go away until I replaced them with some
> thinner but more densely laid bicycle-specific cables.

I take it you made no measurements. Besides, as previously mentioned
any kinks in cable or housing could give length change with cable
tension. This is apparent with a full length cable housing laid out
in some curves and applying tension. The assembly attempts to take
the shortest path and in doing so tries to straighten the housing.

Let's not feed the rumor mill!

--
Jobst Brandt

[Michael Press]

In article <dabac.3a0tz0@no-mx.forums.cyclingforums.com>,
dabac <dabac.3a0tz0@no-mx.forums.cyclingforums.com> wrote:

> jobst.brandt@stanfordalumni.org Wrote:
> > Tom Kunich wrote:
> >
> > >> I also considered using the shifter cable from an old Positron RD
> > >> to see if that would reduce the slack enough to get decent
> > >> performance out of the rear brake, as according to the yachting
> > >> world a solid wire is less springy than a multi strand wire(for a
> > >> given diameter).
> >
> > No matter how closely you pack circular cross section strands,
> > they will have less cross sectional area than an equivalent diameter
> > solid wire, however, for the forces in brake cables, the stranded
> > cables do not stretch.
> >
>
> I fear that this may bog down in another quagmire of semantics,

What is semantics? Most often when `cable stretch' is
used carelessly here it refers to a permanent relative
elongation of the cable path with respect to the housing
path. So a permanent shortening of the cable housing path
is equivalent to a permanent elongation of the brake
cable. Brake cables in use do not permanently elongate
except when individual strands fracture. Brake cables do
elastically elongate and recover. How much do they elongate
elastically? How much does a cable housing path shorten
elastically? How much do brake arms bend elastically?
I expect that the elastic elongation of the cable is the
least of these.

> but
> cables do become longer. It may well be that each individual strand
> doesn't elongate, but a cable as a whole can certainly become longer -
> presumably by the voids in the cross section compressing when the cable
> is under tension. Smaller voids, smaller diameter. And as the diameter
> decreases the virtual center that the strands are wound around gets
> smaller, thus allowing the cable to become longer even if the strands
> themselves aren't stretching.
> I once tried running some nice and thick cables originally intended for
> scooters as brake cables on my bike and they gave a hopelessly mushy
> feel that just didn't go away until I replaced them with some thinner
> but more densely laid bicycle-specific cables.

--
Michael Press

[Tim McNamara]

In article <dabac.3a0tz0@no-mx.forums.cyclingforums.com>,
dabac <dabac.3a0tz0@no-mx.forums.cyclingforums.com> wrote:

> jobst.brandt@stanfordalumni.org Wrote:
> > Tom Kunich wrote:
> >
> > >> I also considered using the shifter cable from an old Positron
> > >> RD to see if that would reduce the slack enough to get decent
> > >> performance out of the rear brake, as according to the yachting
> > >> world a solid wire is less springy than a multi strand wire(for
> > >> a given diameter).
> >
> > No matter how closely you pack circular cross section strands, they
> > will have less cross sectional area than an equivalent diameter
> > solid wire, however, for the forces in brake cables, the stranded
> > cables do not stretch.
> >
>
> I fear that this may bog down in another quagmire of semantics, but
> cables do become longer. It may well be that each individual strand
> doesn't elongate, but a cable as a whole can certainly become longer
> - presumably by the voids in the cross section compressing when the
> cable is under tension. Smaller voids, smaller diameter. And as the
> diameter decreases the virtual center that the strands are wound
> around gets smaller, thus allowing the cable to become longer even if
> the strands themselves aren't stretching.

How much stretch did you measure in the cables? This is one of those
"one measurement is worth a thousand opinions." Where's Fogel Labs when
you need 'em?

[Tom Kunich]

"jim beam" <spamvortex@bad.example.net> wrote in message
news:0oSdncOi6pfYLaHVnZ2dnUVZ_o_inZ2d@speakeasy.ne t...
> jobst.brandt@stanfordalumni.org, although we have to wonder how he ever
> graduated, wrote:
>
>> As was mentioned, caliper arms act in bending against
>> elastomeric brake pads, causing elasticity in brake response.
>
> actually jobst, you know how the rear brake system is more elastic than
> the front? well, that's 100% because of cable/cable run elasticity. the
> pads cancel out of that equation.

Jim. if you don't understand what Jobst is talking about why are you making
such stupid statements? Remove a flexible cable that stretches x. Replace it
with a stiffer cable that doesn't flex and now the pads compress. How do you
tell the difference?

> typical ill-considered presumptive jobstian nonsense. the pads, because
> of low force per area, won't deflect much. a nice long cable run otoh
> most definitely will. as will calipers, levers, and even frames where the
> brakes are cantilever.

Have you ever bothered to actually LOOK at the braking system on a bicycle?
The entire mechanism is flexible because it's being made as light as
possible.

> again, check lever displacement per unit force comparison between front
> and rear. with caliper brakes, that easily determined differential is
> simply cable elasticity.

When did you developed the ability to tell the difference between 15 ft/lbs
and 17 ft/lbs of force manually?

[clare at snyder dot ontario dot canada]

On Tue, 27 May 2008 20:54:03 -0700, "Tom Kunich" <cyclintom@yahoo.
com> wrote:

>"jim beam" <spamvortex@bad.example.net> wrote in message
>news:0oSdncOi6pfYLaHVnZ2dnUVZ_o_inZ2d@speakeasy.ne t...
>> jobst.brandt@stanfordalumni.org, although we have to wonder how he ever
>> graduated, wrote:
>>
>>> As was mentioned, caliper arms act in bending against
>>> elastomeric brake pads, causing elasticity in brake response.
>>
>> actually jobst, you know how the rear brake system is more elastic than
>> the front? well, that's 100% because of cable/cable run elasticity. the
>> pads cancel out of that equation.
>
>Jim. if you don't understand what Jobst is talking about why are you making
>such stupid statements? Remove a flexible cable that stretches x. Replace it
>with a stiffer cable that doesn't flex and now the pads compress. How do you
>tell the difference?
>
>> typical ill-considered presumptive jobstian nonsense. the pads, because
>> of low force per area, won't deflect much. a nice long cable run otoh
>> most definitely will. as will calipers, levers, and even frames where the
>> brakes are cantilever.
>
>Have you ever bothered to actually LOOK at the braking system on a bicycle?
>The entire mechanism is flexible because it's being made as light as
>possible.
>
>> again, check lever displacement per unit force comparison between front
>> and rear. with caliper brakes, that easily determined differential is
>> simply cable elasticity.
>
>When did you developed the ability to tell the difference between 15 ft/lbs
>and 17 ft/lbs of force manually?

Not hard to tell if a cable is stretching (or cable sheath
compressing).Particularly on a "V" brake.
Measure the distance between the tops of the brake "caliper" arms with
the brake handle pulled just past firm contact, then squeeze the
handle hard and see if the measurement changes. If the handles get
closer to the bar without that measurement changing it IS the cables -
not the brake "caliper" arms or pads, or anything else.
** Posted from http://www.teranews.com **

[jobst.brandt@stanfordalumni.org]

Michael Press wrote:

>>>>> I also considered using the shifter cable from an old Positron
>>>>> RD to see if that would reduce the slack enough to get decent
>>>>> performance out of the rear brake, as according to the yachting
>>>>> world a solid wire is less springy than a multi strand wire(for
>>>>> a given diameter).

>>> No matter how closely you pack circular cross section strands,
>>> they will have less cross sectional area than an equivalent
>>> diameter solid wire, however, for the forces in brake cables, the
>>> stranded cables do not stretch.

>> I fear that this may bog down in another quagmire of semantics,

> What is semantics? Most often when "cable stretch" is used
> carelessly here it refers to a permanent relative elongation of the
> cable path with respect to the housing path.

That my be in some exchanges, but "stretch" is most often claimed to
be an elastic feeling "sponginess" which is not housing shortening or
cable elongating temporarily or permanently. To relegate that to semantics
is a dodgy by the believers in hocus-pocus.

> So a permanent shortening of the cable housing path is equivalent to
> a permanent elongation of the brake cable. Brake cables in use do
> not permanently elongate except when individual strands fracture.

Cable strands only fracture when they have been worn about half trough
by a sharp bend in the cable housing and this is a result of fatigue
cracking in the worn surface and loss of cross section. Unless there
was sabotage, single cable strands do not fracture. However if one
strand is worn significantly, all strands are equally worn because,
being wound helically, they all pass the inside of the sharp turn and
wear equally. I have analyzed such failures.

> Brake cables do elastically elongate and recover. How much do they
> elongate elastically? How much does a cable housing path shorten
> elastically? How much do brake arms bend elastically? I expect
> that the elastic elongation of the cable is the least of these.

Just by stating that this occurs is a disservice to readers who are
not mechanical engineers or metallurgists. Leave elastic elongation
to the modulus of elasticity of steel, an amount one cannot feel, it
being an insignificant fraction of hand lever and caliper flex. Leave
the cable out of brake response other than friction.

>> but cables do become longer. It may well be that each individual
>> strand doesn't elongate, but a cable as a whole can certainly
>> become longer - presumably by the voids in the cross section
>> compressing when the cable is under tension. Smaller voids,
>> smaller diameter. And as the diameter decreases the virtual center
>> that the strands are wound around gets smaller, thus allowing the
>> cable to become longer even if the strands themselves aren't
>> stretching. I once tried running some nice and thick cables
>> originally intended for scooters as brake cables on my bike and
>> they gave a hopelessly mushy feel that just didn't go away until I
>> replaced them with some thinner but more densely laid
>> bicycle-specific cables.

I think you should investigate your "void" theory, make a dead-weight
load test measuring cable elongation, and microscopically inspect
cable housing coils for yielded compression marks in the coiled wire.
That there is elastic elongation in structural cables is shown by
their behavior in failure by coiling back to the endpoints. Bicycle
brake cables never approach yield stress and don't present the hazard
of a free standing cable. Even solid wire, (railway contact wire) on
electric railways respond with snap-back coiling if fractured.

To conjure a visual image of brake or control cable stretch here is
fiction. Consider that brake calipers are loaded in bending and that
they press on "rubber" brake pads that, in time, develop toe-in from
elasticity of brake arms and that appears as elastic motion.

Jobst Brandt

[dabac]

Tim McNamara Wrote:
> How much stretch did you measure in the cables?

Well, it did stretch enough for the rear brake lever to routinely
bottom out against the bar if the brake was set up for decent mud
clearance when I was running cantis. W/o a similar setup immediately at
hand to compare with I'd have to guess - 3 mm perhaps. Lock-up was well
within reach of the barrel adjuster - as long as you were willing to
accept a significant drag.

I'll have a look in the parts bin tomorrow - it might just be that I
didn't have the heart to throw away an uncut and barely used length of
cable despite the poor results it was giving.


--
dabac

[jobst.brandt@stanfordalumni.org]

someone wrote:

>> How much stretch did you measure in the cables?

> Well, it did stretch enough for the rear brake lever to routinely
> bottom out against the bar if the brake was set up for decent mud
> clearance when I was running cantis. W/o a similar setup
> immediately at hand to compare with I'd have to guess - 3 mm
> perhaps. Lock-up was well within reach of the barrel adjuster - as
> long as you were willing to accept a significant drag.

> I'll have a look in the parts bin tomorrow - it might just be that I
> didn't have the heart to throw away an uncut and barely used length
> of cable despite the poor results it was giving.

I don't see how cable stretch can be determined from hand lever
motion. As was mentioned, caliper arms act in bending against
elastomeric brake pads, causing elasticity in brake response. Next
time try bringing brake pads into firm contact with the rim and
determine how much cable movement occurs where it leaves the housing
anchor, compared to cable motion at the hand lever. That test occurs
at the higher cable tension portion of brake application.

Jobst Brandt

[dabac]

jobst.brandt@stanfordalumni.org Wrote:
>
> I don't see how cable stretch can be determined from hand lever
> motion.

If "nothing" else changes in either set-up or riding conditions other
than a switch from cable A to cable B, then what other reasons are there
for not getting wheel lock prior to bottoming out with one cable when it
turns out to be consistently possible with another?

An amazing amount of cable housing seating occurring during the first
half mile of the 2nd ride that for some reason just didn't happen during
the 3 miles of the 1st ride?


--
dabac

[carlfogel@comcast.net]

On Mon, 26 May 2008 21:41:17 -0700, "Kerry Montgomery"
<kamontgo@teleport.com> wrote:

>
><carlfogel@comcast.net> wrote in message
>news:c0um34dtb988psm980snfmcl2qr7j3ej6t@4ax.com...
>> On Mon, 26 May 2008 20:59:46 -0500, Tim McNamara
>> <timmcn@bitstream.net> wrote:
>>
>>>In article <d3fm34l9aanijigkbs9a6ppkplrfiacral@4ax.com>,
>>> carlfogel@comcast.net wrote:
>>>
>>>> On Mon, 26 May 2008 16:07:21 -0500, Tim McNamara
>>>> <timmcn@bitstream.net> wrote:
>>
>>>> >How much stretch did you measure in the cables? This is one of
>>>> >those "one measurement is worth a thousand opinions." Where's Fogel
>>>> >Labs when you need 'em?
>>>>
>>>> Dear Tim,
>>>>
>>>> Fogel Labs is suffering--achoo!--a cold probably caught in the line
>>>> of duty while visiting a fantastic private highwheeler museum.
>>>
>>>Feel better soon, Carl!
>>
>> Dear Tim,
>>
>> Thanks--on my ride today I was croaking "On your left!" so feebly that
>> I actually forgave some of the holiday idiots for not hearing me.
>>
>> Here's an example of the kind of stuff at the museum that might appeal
>> to machinists like Chalo, a solid restoration hub machined as a copy
>> of a late-model highwheeler hub:
>> http://i29.tinypic.com/2eurklc.jpg
>>
>> The heads of the direct spokes slip sideways into place in the hub
>> slots, which are all angled slightly inward for the dishing.
>>
>> You can imagi