Help! Fitting a rear mech

[Duncan Smith]

I tried to change the (suspected bent) LX rear mech to one of the
newer less protruding XT ones on the MTB. Everything goes good when
the chain is on the biggest ring - get full range of the cassette from
the indexed pod selector - no problem.

But, on the middle chain-ring, when the smallest outermost sprockets
are selected the pulley cage doesn't take up the enough slack. When
the granny-gear ring is selected the chain is almost dragging on the
floor. Chain length is sufficient to enable the large ring and large
sprocket (with having to pull on the mech about one links worth).

The pulley cage is sprung so that it does pull the chain back - so I
don't think it's mounted incorrectly or anything. Any ideas what I
might have done wrong?

Thanks,

Duncan

[Lou Holtman]

Duncan Smith wrote:
> I tried to change the (suspected bent) LX rear mech to one of the
> newer less protruding XT ones on the MTB. Everything goes good when
> the chain is on the biggest ring - get full range of the cassette from
> the indexed pod selector - no problem.
>
> But, on the middle chain-ring, when the smallest outermost sprockets
> are selected the pulley cage doesn't take up the enough slack. When
> the granny-gear ring is selected the chain is almost dragging on the
> floor. Chain length is sufficient to enable the large ring and large
> sprocket (with having to pull on the mech about one links worth).
>
> The pulley cage is sprung so that it does pull the chain back - so I
> don't think it's mounted incorrectly or anything. Any ideas what I
> might have done wrong?

Is your chainlength really correct, compared to the 'old sitiuation'?

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)

[landotter]

On Oct 21, 8:52 am, Duncan Smith <DSmith1...@googlemail.com> wrote:
> I tried to change the (suspected bent) LX rear mech to one of the
> newer less protruding XT ones on the MTB. Everything goes good when
> the chain is on the biggest ring - get full range of the cassette from
> the indexed pod selector - no problem.
>
> But, on the middle chain-ring, when the smallest outermost sprockets
> are selected the pulley cage doesn't take up the enough slack. When
> the granny-gear ring is selected the chain is almost dragging on the
> floor. Chain length is sufficient to enable the large ring and large
> sprocket (with having to pull on the mech about one links worth).
>
> The pulley cage is sprung so that it does pull the chain back - so I
> don't think it's mounted incorrectly or anything. Any ideas what I
> might have done wrong?


Increase b-screw tension which tightens the dérailleur pivot spring.

[Hank Wirtz]

On Oct 21, 6:52 am, Duncan Smith <DSmith1...@googlemail.com> wrote:
> I tried to change the (suspected bent) LX rear mech to one of the
> newer less protruding XT ones on the MTB. Everything goes good when
> the chain is on the biggest ring - get full range of the cassette from
> the indexed pod selector - no problem.
>
> But, on the middle chain-ring, when the smallest outermost sprockets
> are selected the pulley cage doesn't take up the enough slack. When
> the granny-gear ring is selected the chain is almost dragging on the
> floor. Chain length is sufficient to enable the large ring and large
> sprocket (with having to pull on the mech about one links worth).
>
> The pulley cage is sprung so that it does pull the chain back - so I
> don't think it's mounted incorrectly or anything. Any ideas what I
> might have done wrong?
>
> Thanks,
>
> Duncan

Check the part number of the new one. Does it say GS or SGS? If it's
GS, you got the medium cage model, which probably doesn't have enough
wrap capacity.

[A Muzi]

Duncan Smith wrote:
> I tried to change the (suspected bent) LX rear mech to one of the
> newer less protruding XT ones on the MTB. Everything goes good when
> the chain is on the biggest ring - get full range of the cassette from
> the indexed pod selector - no problem.
>
> But, on the middle chain-ring, when the smallest outermost sprockets
> are selected the pulley cage doesn't take up the enough slack. When
> the granny-gear ring is selected the chain is almost dragging on the
> floor. Chain length is sufficient to enable the large ring and large
> sprocket (with having to pull on the mech about one links worth).
>
> The pulley cage is sprung so that it does pull the chain back - so I
> don't think it's mounted incorrectly or anything. Any ideas what I
> might have done wrong?

Did you get the short "GS" or the long "SGS" model?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[Duncan Smith]

On Oct 21, 3:31 pm, Lou Holtman <lholremovet...@planet.nl> wrote:
> Duncan Smith wrote:
> > I tried to change the (suspected bent) LX rear mech to one of the
> > newer less protruding XT ones on the MTB. Everything goes good when
> > the chain is on the biggest ring - get full range of the cassette from
> > the indexed pod selector - no problem.
>
> > But, on the middle chain-ring, when the smallest outermost sprockets
> > are selected the pulley cage doesn't take up the enough slack. When
> > the granny-gear ring is selected the chain is almost dragging on the
> > floor. Chain length is sufficient to enable the large ring and large
> > sprocket (with having to pull on the mech about one links worth).
>
> > The pulley cage is sprung so that it does pull the chain back - so I
> > don't think it's mounted incorrectly or anything. Any ideas what I
> > might have done wrong?
>
> Is your chainlength really correct, compared to the 'old sitiuation'?
>

Same length as the old one exactly, then I took a link out and found
it was a bit of a stretch when on the largest ring and sprocket - so
put it back again...

[Duncan Smith]

On Oct 21, 3:42 pm, landotter <landot...@gmail.com> wrote:
> On Oct 21, 8:52 am, Duncan Smith <DSmith1...@googlemail.com> wrote:
>
> > I tried to change the (suspected bent) LX rear mech to one of the
> > newer less protruding XT ones on the MTB. Everything goes good when
> > the chain is on the biggest ring - get full range of the cassette from
> > the indexed pod selector - no problem.
>
> > But, on the middle chain-ring, when the smallest outermost sprockets
> > are selected the pulley cage doesn't take up the enough slack. When
> > the granny-gear ring is selected the chain is almost dragging on the
> > floor. Chain length is sufficient to enable the large ring and large
> > sprocket (with having to pull on the mech about one links worth).
>
> > The pulley cage is sprung so that it does pull the chain back - so I
> > don't think it's mounted incorrectly or anything. Any ideas what I
> > might have done wrong?
>
> Increase b-screw tension which tightens the dérailleur pivot spring.

It was a tight as it would go...

[Duncan Smith]

On Oct 21, 3:49 pm, Hank Wirtz <h...@wirtznet.net> wrote:
> On Oct 21, 6:52 am, Duncan Smith <DSmith1...@googlemail.com> wrote:
>
>
>
> > I tried to change the (suspected bent) LX rear mech to one of the
> > newer less protruding XT ones on the MTB. Everything goes good when
> > the chain is on the biggest ring - get full range of the cassette from
> > the indexed pod selector - no problem.
>
> > But, on the middle chain-ring, when the smallest outermost sprockets
> > are selected the pulley cage doesn't take up the enough slack. When
> > the granny-gear ring is selected the chain is almost dragging on the
> > floor. Chain length is sufficient to enable the large ring and large
> > sprocket (with having to pull on the mech about one links worth).
>
> > The pulley cage is sprung so that it does pull the chain back - so I
> > don't think it's mounted incorrectly or anything. Any ideas what I
> > might have done wrong?
>
> > Thanks,
>
> > Duncan
>
> Check the part number of the new one. Does it say GS or SGS? If it's
> GS, you got the medium cage model, which probably doesn't have enough
> wrap capacity.

Thrown the box away now, but I'm pretty sure it was a GS. The bike's
a 2007 Rock-hopper. Where would incompatibility arise from - the
frame, chain-rings?

Thanks,

Duncan

[Steve Gravrock]

On 2007-10-21, Duncan Smith <DSmith1974@googlemail.com> wrote:
> On Oct 21, 3:49 pm, Hank Wirtz <h...@wirtznet.net> wrote:

>> Check the part number of the new one. Does it say GS or SGS? If it's
>> GS, you got the medium cage model, which probably doesn't have enough
>> wrap capacity.
>
> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
> a 2007 Rock-hopper. Where would incompatibility arise from - the
> frame, chain-rings?

It comes from the overall range of gearing. The cage length determines
how much chain slack it can take up. For a normal mountain bike
drivetrain you need the long cage SGS model.

[landotter]

On Oct 21, 2:05 pm, Duncan Smith <DSmith1...@googlemail.com> wrote:
> On Oct 21, 3:49 pm, Hank Wirtz <h...@wirtznet.net> wrote:
>
>
>
> > On Oct 21, 6:52 am, Duncan Smith <DSmith1...@googlemail.com> wrote:
>
> > > I tried to change the (suspected bent) LX rear mech to one of the
> > > newer less protruding XT ones on the MTB. Everything goes good when
> > > the chain is on the biggest ring - get full range of the cassette from
> > > the indexed pod selector - no problem.
>
> > > But, on the middle chain-ring, when the smallest outermost sprockets
> > > are selected the pulley cage doesn't take up the enough slack. When
> > > the granny-gear ring is selected the chain is almost dragging on the
> > > floor. Chain length is sufficient to enable the large ring and large
> > > sprocket (with having to pull on the mech about one links worth).
>
> > > The pulley cage is sprung so that it does pull the chain back - so I
> > > don't think it's mounted incorrectly or anything. Any ideas what I
> > > might have done wrong?
>
> > > Thanks,
>
> > > Duncan
>
> > Check the part number of the new one. Does it say GS or SGS? If it's
> > GS, you got the medium cage model, which probably doesn't have enough
> > wrap capacity.
>
> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
> a 2007 Rock-hopper. Where would incompatibility arise from - the
> frame, chain-rings?
>
> Thanks,
>
> Duncan

The gearing in general. Your medium cage GS doesn't have the capacity
for your particular gearing.

See the difference:

http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-SGS.jpg
http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-GS.jpg

[A Muzi]

>> Duncan Smith <DSmith1...@googlemail.com> wrote:
>>> I tried to change the (suspected bent) LX rear mech to one of the
>>> newer less protruding XT ones on the MTB. Everything goes good when
>>> the chain is on the biggest ring - get full range of the cassette from
>>> the indexed pod selector - no problem.
>>> But, on the middle chain-ring, when the smallest outermost sprockets
>>> are selected the pulley cage doesn't take up the enough slack. When
>>> the granny-gear ring is selected the chain is almost dragging on the
>>> floor. Chain length is sufficient to enable the large ring and large
>>> sprocket (with having to pull on the mech about one links worth).
>>> The pulley cage is sprung so that it does pull the chain back - so I
>>> don't think it's mounted incorrectly or anything. Any ideas what I
>>> might have done wrong?

> Hank Wirtz <h...@wirtznet.net> wrote:
>> Check the part number of the new one. Does it say GS or SGS? If it's
>> GS, you got the medium cage model, which probably doesn't have enough
>> wrap capacity.

Duncan Smith wrote:
> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
> a 2007 Rock-hopper. Where would incompatibility arise from - the
> frame, chain-rings?

Measure the distance between pulleys on old and new. You may have
replaced an "SGS" with a "GS"
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[Steve Gravrock]

On 2007-10-21, landotter <landotter@gmail.com> wrote:
> On Oct 21, 2:05 pm, Duncan Smith <DSmith1...@googlemail.com> wrote:

>> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
>> a 2007 Rock-hopper. Where would incompatibility arise from - the
>> frame, chain-rings?
>>
>> Thanks,
>>
>> Duncan
>
> The gearing in general. Your medium cage GS doesn't have the capacity
> for your particular gearing.
>
> See the difference:
>
> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-SGS.jpg
> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-GS.jpg

Why does Shimano even bother to make medium cage mountain bike
derailers? Aside from the 1x9 crowd, which isn't big enough for Shimano
to bother with, I don't see anything newer than my old 7 speed that
could use one of those. I suppose you could put one on a road bike, but
that market's already taken care of.

[datakoll]

loosen the cable screw, with system in small outboard cog, pull cable
with vise grips { clamp jaws on cable end just snugly then use screw
to tighten} tight, pull deray cage to cycles rearward, then with
third hand tighten (still pulling cable tight ) cabe screw, fastening
taught cable.
That's avariable adjustment in conjunction with the deray screw found
at the frame/deray area mounted on the deray/frame bolt bushing. Screw
that screw in but don't force it. Find a way to not force it and screw
in.

[A Muzi]

>> Duncan Smith <DSmith1...@googlemail.com> wrote:
>>> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
>>> a 2007 Rock-hopper. Where would incompatibility arise from - the
>>> frame, chain-rings?

> landotter <landotter@gmail.com> wrote:
>> The gearing in general. Your medium cage GS doesn't have the capacity
>> for your particular gearing.
>> See the difference:
>> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-SGS.jpg
>> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-GS.jpg

Steve Gravrock wrote:
> Why does Shimano even bother to make medium cage mountain bike
> derailers? Aside from the 1x9 crowd, which isn't big enough for Shimano
> to bother with, I don't see anything newer than my old 7 speed that
> could use one of those. I suppose you could put one on a road bike, but
> that market's already taken care of.

As Peter quotes often, "It's for selling".
In any LBS, a popular question is 'which is lighter?' among other
queries of similar depth.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[M-gineering]

A Muzi wrote:
>>> Duncan Smith <DSmith1...@googlemail.com> wrote:
>>>> Thrown the box away now, but I'm pretty sure it was a GS. The bike's
>>>> a 2007 Rock-hopper. Where would incompatibility arise from - the
>>>> frame, chain-rings?
>
>> landotter <landotter@gmail.com> wrote:
>>> The gearing in general. Your medium cage GS doesn't have the capacity
>>> for your particular gearing.
>>> See the difference:
>>> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-SGS.jpg
>>> http://www.starbike.com/images/Shimano/Deore_LX/hires/RD-M580-GS.jpg
>
> Steve Gravrock wrote:
>> Why does Shimano even bother to make medium cage mountain bike
>> derailers? Aside from the 1x9 crowd, which isn't big enough for Shimano
>> to bother with, I don't see anything newer than my old 7 speed that
>> could use one of those. I suppose you could put one on a road bike, but
>> that market's already taken care of.
>
> As Peter quotes often, "It's for selling".
> In any LBS, a popular question is 'which is lighter?' among other
> queries of similar depth.

If you're stuck in flatland, 28 is a BIG cog and a medium cage is fine
(with a road cassette ;))

--
/Marten

info(apestaartje)m-gineering(punt)nl

[datakoll]

- delete irrelevant text -

anyway, I was under the impression a chain going around large CR and
large cog could be one inch - two link sections - too long: maybe two.
do you have a sram powerlink on hand? so the chain can be chopped and
fitted? and a 5 foot chain board to lay the chain on for link counting?

[Duncan Smith]

On Oct 21, 11:57 pm, datakoll <datak...@yahoo.com> wrote:
> - delete irrelevant text -
>
> anyway, I was under the impression a chain going around large CR and
> large cog could be one inch - two link sections - too long: maybe two.
> do you have a sram powerlink on hand? so the chain can be chopped and
> fitted? and a 5 foot chain board to lay the chain on for link counting?

Boy do I feel silly! I took the mech off to try and find GS or SGS
serial code and then replaced it to take it to the shop. Only when I
replaced it I noticed the deray housing was now touching the drop out
and the chain cage was angled back much further - fitted the chain did
the H/L/Index settings - works a treat. At least I found it out
before returning it to the shop.

Thanks for all the suggestions..

Duncan

[A Muzi]

> datakoll <datak...@yahoo.com> wrote:
>> - delete irrelevant text -
>> anyway, I was under the impression a chain going around large CR and
>> large cog could be one inch - two link sections - too long: maybe two.
>> do you have a sram powerlink on hand? so the chain can be chopped and
>> fitted? and a 5 foot chain board to lay the chain on for link counting?

Duncan Smith wrote:
> Boy do I feel silly! I took the mech off to try and find GS or SGS
> serial code and then replaced it to take it to the shop. Only when I
> replaced it I noticed the deray housing was now touching the drop out
> and the chain cage was angled back much further - fitted the chain did
> the H/L/Index settings - works a treat. At least I found it out
> before returning it to the shop.

r.b.t. protocol violation:
Only Gene is allowed to call a gear changer a 'deray'.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

[velodancer]

> Boy do I feel silly! I took the mech off to try and find GS or SGS
> serial code and then replaced it to take it to the shop. Only when I
> replaced it I noticed the deray housing was now touching the drop out
> and the chain cage was angled back much further - fitted the chain did
> the H/L/Index settings - works a treat. At least I found it out
> before returning it to the shop.

Glad you solved your problem. There are some significant differences
in the new Shadow derailleurs though. Besides the low profile, there
are three other major changes: a more direct cable pull (reduced loop
in the cable housing), removal of the B tension spring, and centering
of the guide pulley on the cage pivot. The direct cable routing is
clearly better. The next two changes are only an advantage for Horst
link bikes as they prevent the derailleur from hitting the chainstay.
This issue is clearly demonstrated by the infamous videos of SRAM
versus Shimano rear derailleurs:
http://www.youtube.com/watch?v=tYL_Vc4hU1U
http://www.youtube.com/watch?v=NYKvCLC23ww

I talked to a senior Shimano guy at the show and he said that shifting
is not improved by these changes. Most customers with OE drivetrains
will not be able to notice any difference other than reduced ability
to misadjust cable tension (for example good shifting will occur only
within one turn of the barrel adjuster rather then two turns). I can
only assume that Specialized is a large enough customer to make this
reduction in shifting quality worthwhile enough to raise eyebrows at
apparent adoption of SRAM derailleur design.

As the B pivot is now essentially fixed, this required two other
changes in this derailleur design. Because the derailleur can no
longer "float", it cannot follow the change in cog size as accurately.
This is exacerbated by the lack of an offset guide pulley. Thus the
cage angle has been significantly increased compared to help it track
the cogs better. This makes it less flexible for a variety of cog sets
and indeed Shimano specs this derailleur as being for 11-32/34t
clusters only.

For a similar reason, it does not have the inherent chain wrap
capacity of derailleurs with B tension springs. Thus you will notice
that the cage is significantly longer than the old design to
compensate. In fact, the long cage version is probably the longest
cage I have ever seen.

Because of the lack of the B spring, tension of the pulley spring had
to be increased. The Shimano rep told me that this translates into a
15 percent higher force required on the cable (probably unnoticeable
but still significant).

I purchased the XT Shadow long cage before I went to Interbike based
on what I thought were real design improvements at the time. After
Interbike I wished I hadn't, particularly after my trial last week of
two very different derailleurs. As background, I have a non OE very
wide range (9-34t) cogset with custom cog selection (Shimano). As
such, my setup is ideal for testing derailleur's abilities on marginal
systems.

I'd been using a SRAM X-O derailleur for some months. Switching to an
older XT derailleur (and appropriate shifter) brought about
significant gains. While subjective, I would say shifting improved
about 20 percent.

In addition, one thing often noted about SRAM derailleurs is that
upshifting (to a smaller cog) is done with a noticeable clunk, both
audible and tactile. Because of the way my XT B spring derailleur
follows the cogs closer, upshifts are much smoother. If performance
was otherwise the same, this one factor would be enough for me to
switch.

As a result of this, I don't even see the point of trialing my new
Shadow XT for my purposes (I'll probably sell it on eBay). For others,
you would have to consider carefully your choices. Horst link owner?
That is a no brainer. Often hit your derailleur on protrusions? Maybe.
I looked at my older derailleurs and noticed a number of dings. Don't
have a wide cluster? Then no. I wish Shimano would put the more direct
cable routing on all their derailleurs but unless you are unwilling to
go the Avid Rollamajig route, that shouldn't be a major factor. SRAM
versus the Shadow? The increased cable pull of the SRAM is a minor
technical advantage.

One other thing to consider when switching from standard Shimano to
SRAM or the new Shadow if you have a full suspension bike is proper
chain length. You will likely need to add a chain link or two. SRAM
derailleurs have a reputation for self destruction on the trail. I'm
convinced this happens because of chain growth at full bump.
Derailleurs with a B tension spring have much better wrap and ability
to shrug off poor chain length selection.

On other thing noteworthy I've discovered with my less than optimal
setup is that Shimano chains shift better on Shimano clusters than
SRAM chains. It was very minor but noticeable. I was very surprised by
this and almost didn't bother trialing the Shimano chain because I
could not see a visual difference in inner plate profile - they looked
absolutely identical.

[Tom Sherman]

Andrew Muzi mused:
- delete unimportant text - [1]
> Duncan Smith wrote:
>> Boy do I feel silly! I took the mech off to try and find GS or SGS
>> serial code and then replaced it to take it to the shop. Only when I
>> replaced it I noticed the deray housing was now touching the drop out
>> and the chain cage was angled back much further - fitted the chain did
>> the H/L/Index settings - works a treat. At least I found it out
>> before returning it to the shop.
>
> r.b.t. protocol violation:
> Only Gene is allowed to call a gear changer a 'deray'.

butbutbut [2], it is OK as long as it is footnoted as a gdanielsism.

[1] Gratuitous gdanielsism.
[2] ibid.

--
Tom Sherman - Holstein-Friesland Bovinia
Beer - It's not just for breakfast anymore!

[Duncan Smith]

>
> > r.b.t. protocol violation:
> > Only Gene is allowed to call a gear changer a 'deray'.
>
> butbutbut [2], it is OK as long as it is footnoted as a gdanielsism.
>
> [1] Gratuitous gdanielsism.
> [2] ibid.
>

I have no idea what either of you are talking about! Sorry...

Regards,

Duncan

[Tom Sherman]

Duncan Smith wrote:
>>> r.b.t. protocol violation:
>>> Only Gene is allowed to call a gear changer a 'deray'.
>> butbutbut [2], it is OK as long as it is footnoted as a gdanielsism.
>>
>> [1] Gratuitous gdanielsism.
>> [2] ibid.
>>
>
> I have no idea what either of you are talking about! Sorry...

Google Groups search "datakoll".

--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?