Seat post collar for carbon seat post

[cycledogg]

Hello,
I am installing a Cannondale brand carbon seat post on a Cannondale
Optimo frame. The instructions state to mount the collar with the bolt
facing towards the front on the bike. I see many other bikes
(including the pro's) with the collar facing the rear normal position.
Will it make a safety issue to install it the "normal" way or should I
do like Cannondale recommends?
Cheers,
Rick in Tennessee

[jim beam]

cycledogg wrote:
> Hello,
> I am installing a Cannondale brand carbon seat post on a Cannondale
> Optimo frame. The instructions state to mount the collar with the bolt
> facing towards the front on the bike. I see many other bikes
> (including the pro's) with the collar facing the rear normal position.
> Will it make a safety issue to install it the "normal" way or should I
> do like Cannondale recommends?
> Cheers,
> Rick in Tennessee


unless both the head and the shaft of the collar bolt are mounted inside
pivots, then the clamp, when tightened, goes out of round, and thus can
raise the clamping force at certain points on its circumference. with a
carbon post, this can cause cracking, and thus, loss of strength. the
way to minimize this effect is to mount the collar to the front - the
out of round for the collar is kinda-sorta offset by a similar effect
from the slot in the seat tube.

to summarize: do what the manufacturer says.

[Michael Press]

In article
<d4931ee8-6eea-4380-a91a-2c0d76efdedd@k2g2000hse.googlegroups.com>,
cycledogg <cycledogg@hotmail.com> wrote:

> Hello,
> I am installing a Cannondale brand carbon seat post on a Cannondale
> Optimo frame. The instructions state to mount the collar with the bolt
> facing towards the front on the bike. I see many other bikes
> (including the pro's) with the collar facing the rear normal position.
> Will it make a safety issue to install it the "normal" way or should I
> do like Cannondale recommends?

Seat post clamps and seat tube split tops are not
round. That is to say they are not round at the bolt
and at the seat tube split respectively. When the clamp
is tightened, it forms a flat spot where the broken
ring is drawn together. Hence, if the bolt and the seat
tube split are matched up, they form a flat spot, and
the overall clamping action is not round. The edges of
the seat tube split are forced directly inward where
they chafe on the seat post, gouging the delicate
carbon fibre. When you spin the seat post clamp around
half a revolution the seat tube split is under the
round portion of the seat post clamp. This portion of
the seat post clamp does not flatten, so the edges of
the seat tube split remain round. The round part of
the seat tube is under the potential flat spot of the
seat post clamp. The overall effect is to make the
entire assembly as round as possible.

--
Michael Press

[sergio]

On Mar 4, 4:26 am, jim beam <spamvor...@bad.example.net> wrote:

> to summarize: do what the manufacturer says.

Wouldn't it be wiser to do otherwise and to entirely spare oneself
such delicate solutions?

Sergio
Pisa

[Bill]

"Michael Press" <rubrum@pacbell.net> wrote in message
news:rubrum-D1C68B.21524703032008@news.sf.sbcglobal.net...
> In article
> <d4931ee8-6eea-4380-a91a-2c0d76efdedd@k2g2000hse.googlegroups.com>,
> cycledogg <cycledogg@hotmail.com> wrote:
>
>> Hello,
>> I am installing a Cannondale brand carbon seat post on a Cannondale
>> Optimo frame. The instructions state to mount the collar with the bolt
>> facing towards the front on the bike. I see many other bikes
>> (including the pro's) with the collar facing the rear normal position.
>> Will it make a safety issue to install it the "normal" way or should I
>> do like Cannondale recommends?
>
> Seat post clamps and seat tube split tops are not
> round. That is to say they are not round at the bolt
> and at the seat tube split respectively. When the clamp
> is tightened, it forms a flat spot where the broken
> ring is drawn together. Hence, if the bolt and the seat
> tube split are matched up, they form a flat spot, and
> the overall clamping action is not round. The edges of
> the seat tube split are forced directly inward where
> they chafe on the seat post, gouging the delicate
> carbon fibre. When you spin the seat post clamp around
> half a revolution the seat tube split is under the
> round portion of the seat post clamp. This portion of
> the seat post clamp does not flatten, so the edges of
> the seat tube split remain round. The round part of
> the seat tube is under the potential flat spot of the
> seat post clamp. The overall effect is to make the
> entire assembly as round as possible.
>
> --
> Michael Press

Does the same reasoning apply to split inserts for adapting 1 1/8 to 1"
stems for use with 1" carbon steerer tubes?

[Michael Press]

In article <47cda2a3$0$24081$4c368faf@roadrunner.com>,
"Bill" <bill@example.invalid> wrote:

> "Michael Press" <rubrum@pacbell.net> wrote in message
> news:rubrum-D1C68B.21524703032008@news.sf.sbcglobal.net...
> > In article
> > <d4931ee8-6eea-4380-a91a-2c0d76efdedd@k2g2000hse.googlegroups.com>,
> > cycledogg <cycledogg@hotmail.com> wrote:
> >
> >> Hello,
> >> I am installing a Cannondale brand carbon seat post on a Cannondale
> >> Optimo frame. The instructions state to mount the collar with the bolt
> >> facing towards the front on the bike. I see many other bikes
> >> (including the pro's) with the collar facing the rear normal position.
> >> Will it make a safety issue to install it the "normal" way or should I
> >> do like Cannondale recommends?
> >
> > Seat post clamps and seat tube split tops are not
> > round. That is to say they are not round at the bolt
> > and at the seat tube split respectively. When the clamp
> > is tightened, it forms a flat spot where the broken
> > ring is drawn together. Hence, if the bolt and the seat
> > tube split are matched up, they form a flat spot, and
> > the overall clamping action is not round. The edges of
> > the seat tube split are forced directly inward where
> > they chafe on the seat post, gouging the delicate
> > carbon fibre. When you spin the seat post clamp around
> > half a revolution the seat tube split is under the
> > round portion of the seat post clamp. This portion of
> > the seat post clamp does not flatten, so the edges of
> > the seat tube split remain round. The round part of
> > the seat tube is under the potential flat spot of the
> > seat post clamp. The overall effect is to make the
> > entire assembly as round as possible.
>
> Does the same reasoning apply to split inserts for adapting 1 1/8 to 1"
> stems for use with 1" carbon steerer tubes?

Sorry, I am not familiar with that assembly. If there
is a clamp similar to the seat post clamp, a split tube
to be drawn inward, and no other competing
considerations, then yes. <:^}

An everyday assembly that benefits from this
consideration is the twist tie used to close a bag.
Rather than put it on and twist the ends together as
usual; take an extra turn around the bag, then twist
the ends together. It is called a round turn. The
round turn is more secure. While twisting, there is
more mechanical advantage drawing the ligature tight.
The round turn eliminates the cusp at the twist of the
usual method that can foul the bag.

--
Michael Press