Seat Post Slipping - Seat Post Clamp Question



I just got a new bike (Fuji Professional Carbon), and the seatpost I
put in it will not stay put no matter how hard I tighten it (yes, it is
the correct size seatpost).

The seatpost clamp that came with the bike is a piece of ****. I stole
the Salsa seatpost clamp off my TT bike and put it on the Fuji. The
Salsa clamp has nearly twice the clamping area and uses a larger bolt.
I still had to tighten more than I would like to get it to hold, but it
works much better. My concern is that the TT bike uses a larger size
seat post, so I have no idea if the seatpost clamp is truly compatible
between bikes. The Fuji uses a 27.2 seatpost and the TT bike (Guru)
uses a 28.6 seatpost.

Am I good to ride with this for the time being or should I get a
different clamp for the Fuji?

I guess I have to get another clamp anyway because the crappy clamp did
not work any better on the Guru than on the Fuji (although it seemed to
fit okay), but I'd like to ride the next couple days without hassling
with it if possible.

Thanks,

Eric
 
W

Werehatrack

Guest
On 19 Apr 2005 19:40:40 -0700, [email protected] wrote:

>I just got a new bike (Fuji Professional Carbon), and the seatpost I
>put in it will not stay put no matter how hard I tighten it (yes, it is
>the correct size seatpost).
>
>The seatpost clamp that came with the bike is a piece of ****. I stole
>the Salsa seatpost clamp off my TT bike and put it on the Fuji. The
>Salsa clamp has nearly twice the clamping area and uses a larger bolt.
>I still had to tighten more than I would like to get it to hold, but it
>works much better. My concern is that the TT bike uses a larger size
>seat post, so I have no idea if the seatpost clamp is truly compatible
>between bikes. The Fuji uses a 27.2 seatpost and the TT bike (Guru)
>uses a 28.6 seatpost.
>
>Am I good to ride with this for the time being or should I get a
>different clamp for the Fuji?
>
>I guess I have to get another clamp anyway because the crappy clamp did
>not work any better on the Guru than on the Fuji (although it seemed to
>fit okay), but I'd like to ride the next couple days without hassling
>with it if possible.


If the clamp's QR is of a design that makes this an option, remove the
QR assembly from the clamp and replace it with a bolt and nut. The QR
is probably not developing enough clamping pressure.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
 
L

Leo Lichtman

Guest
<[email protected]> wrote: (clip) but I'd like to ride the next couple
days without hassling with it if possible.
^^^^^^^^^^^^^^^
As a temporary fix, while you sort things out, how about putting a hose
clamp on the seat post, positioned and tightened to rest on top os the seat
tube?
 
C

catzz66

Guest
Werehatrack wrote:
>>

> If the clamp's QR is of a design that makes this an option, remove the
> QR assembly from the clamp and replace it with a bolt and nut. The QR
> is probably not developing enough clamping pressure.


Thanks for this advice. I have the same problem on my mtn bike and it
looks like getting rid of the quick release is the fix.
 
Z

Zog The Undeniable

Guest
[email protected] wrote:

> I just got a new bike (Fuji Professional Carbon), and the seatpost I
> put in it will not stay put no matter how hard I tighten it (yes, it is
> the correct size seatpost).
>
> The seatpost clamp that came with the bike is a piece of ****. I stole
> the Salsa seatpost clamp off my TT bike and put it on the Fuji. The
> Salsa clamp has nearly twice the clamping area and uses a larger bolt.
> I still had to tighten more than I would like to get it to hold, but it
> works much better. My concern is that the TT bike uses a larger size
> seat post, so I have no idea if the seatpost clamp is truly compatible
> between bikes. The Fuji uses a 27.2 seatpost and the TT bike (Guru)
> uses a 28.6 seatpost.
>
> Am I good to ride with this for the time being or should I get a
> different clamp for the Fuji?


Seat clamps are a generic spare part. Measure the outside of the seat
tube with a set of calipers and buy a new one of the correct size from a
good bike shop.

Are you sure the seatpost is the right diameter for the frame?
 
D

Donald Gillies

Guest
I had a similar problem two weeks ago and it turned out that i had a
27.0 seatpost in a 27.2 frame tube. the ears of the tube were
incredibly close together (~ 1 mm) and so i changed out the post for a
27.2. that bike is fine now.

this might still be your problem because it's possible that at the
fuji factory they "over-reamed" this particular seat tube.

another possibility is that - like my trek 2300 - your seatpost ears
might be starting to fail. i'd do a careful inspection for any cracks
beginning in and around the seatpost lug. this would prevent you from
getting full force on the seatpost.

my - aluminum - seatpost lugs failed with a shimano ultegra seatpost.
the aluminum seat tube was so perfectly smooth inside that installing
the seatpost did not marr the seatpost at all. because the post was
not marred, its probable that more pressure / friction was required,
which lead to the failure of the seat lug.

i'd check your post to make sure its getting marred upon installation.
you might also sand the inside of the frame lightly with very coarse
paper (150 grit or less) to make sure you have a good friction
interface on the post. this is how you fix a similar problem - when a
micro adjusting saddle clamp is not holding a saddle in place.

- Don Gillies
San Diego, CA
 
J

Jim Adney

Guest
On 19 Apr 2005 19:40:40 -0700 [email protected] wrote:

>I just got a new bike (Fuji Professional Carbon), and the seatpost I
>put in it will not stay put no matter how hard I tighten it (yes, it is
>the correct size seatpost).


How do you know that it's the "right" size?

-
-----------------------------------------------
Jim Adney [email protected]
Madison, WI 53711 USA
-----------------------------------------------
 
The best solution I've found for stopping slipping seat posts is to
clean the post and inside the seat tube with acetone. Has worked every
time for me, on four different carbon frames with five different carbon
and two aluminum seat posts. No other change made as much difference in
preventing slipping.

Cleaning it doesn't cost much, and it's worth a try, especially because
you have a carbon frame. Just wet a white paper towel with acetone,
scrub in the frame and on the post, then repeat until the towel comes
out clean.
 
D

dvt

Guest
[email protected] wrote:
> The best solution I've found for stopping slipping seat posts is to
> clean the post and inside the seat tube with acetone. Has worked every
> time for me, on four different carbon frames with five different carbon
> and two aluminum seat posts. No other change made as much difference in
> preventing slipping.
>
> Cleaning it doesn't cost much, and it's worth a try, especially because
> you have a carbon frame. Just wet a white paper towel with acetone,
> scrub in the frame and on the post, then repeat until the towel comes
> out clean.


Don't let that acetone stay on the carbon for very long! Some epoxies (I
don't know about those used in a typical bike frame) use acetone as a
solvent, and acetone can turn those epoxies to mush.

--
Dave
dvt at psu dot edu
 
T

Ted

Guest
[email protected] wrote:
>I just got a new bike (Fuji Professional Carbon), and the seatpost I
>put in it will not stay put no matter how hard I tighten it (yes, it is
>the correct size seatpost).


Jim Adney wrote:

How do you know that it's the "right" size?


> Why would you ask this question? I know because the bike uses a 27.2
> seatpost and that's what I put in the frame.
>
> Updated info, in case anyone cares:
>
> I've learned that no 27.2 seatpost, including the one that came on the
> bike, actually holds with the original seatpost clamp, and none of my
> teammates that got the same bike are having this same problem. I've
> discovered that when I insert the seatpost that there is actually some
> play in the tube (it is not a tight fit). Is this in anyway normal?
> The bike shop that I got the bike through (which is several hours from
> my home, so I can't just take the bike in) thinks there is a good
> chance the frame is a defect. I'm dismayed by this prospect because it
> took 4 months to get the bike in the first place (and it is a very cool
> bike).


Eric, either the post is too small or the seat tube is too large. I
suspect Jim was suggesting that your 27.2 post may not be that size;
many are not very accurately made.

If you have some good measuring tools (micrometer, calipers) you can
solve the problem. If you don't, try another 27.2 post or two. There's
a good chance you have a friend with that size post, as it's common.

Ted

--
Ted Bennett
Portland, OR
 
M

Mike Jacoubowsky

Guest
> The best solution I've found for stopping slipping seat posts is to
> clean the post and inside the seat tube with acetone. Has worked every
> time for me, on four different carbon frames with five different carbon
> and two aluminum seat posts. No other change made as much difference in
> preventing slipping.


This is correct; there should be no grease between seatpost and a carbon
frame, as it will invariably require far too much clamping force to hold in
place. Acetone might be a bit harsh though; something a bit milder might be
in order (such as alcohol, although I honestly don't know how well alcohol
dissolves grease).

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
 
M

Marvin

Guest
[email protected] wrote:
> Why would you ask this question? I know because the bike uses a 27.2
> seatpost and that's what I put in the frame.
>
> Updated info, in case anyone cares:
>
> I've learned that no 27.2 seatpost, including the one that came on

the
> bike, actually holds with the original seatpost clamp, and none of my
> teammates that got the same bike are having this same problem. I've
> discovered that when I insert the seatpost that there is actually

some
> play in the tube (it is not a tight fit). Is this in anyway normal?
> The bike shop that I got the bike through (which is several hours

from
> my home, so I can't just take the bike in) thinks there is a good
> chance the frame is a defect. I'm dismayed by this prospect because

it
> took 4 months to get the bike in the first place (and it is a very

cool
> bike).


That sounds very much like the seat tube isn't truly 27.2. My usual
solution to this is to properly ream the seat tube to the next largest
size, but you obviously don't want to do that with carbon. It's
possible that you could fit a 27.4 if you can get hold of one (and take
a fraction of a mil off the seatpost if necessary), but you might
prefer to just send the frame back rather than futz around like that.

As has been noted by others, you really don't want grease anywhere near
carbon frames, it's not necessary and tends to cause (or exacerbate)
what you're seeing here.

You also don't want an overtightened clamp anywhere near a carbon
frame, they really don't like excess clamping force.
 
J

Jim Adney

Guest
On 20 Apr 2005 22:03:59 -0700 [email protected] wrote:

>Why would you ask this question? I know because the bike uses a 27.2
>seatpost and that's what I put in the frame.


I asked the question because it's often the case that people assume
that they know the right size without having any real basis for that
belief. Since you say that this post is loose in there, I suspect that
you really need a larger post. I have no way of knowing, from here,
whether the problem is that you need a post larger than 27.2 or that
the post you have is actually smaller than it is labeled.

All I know is that a seat post which is too small will never be secure
in the frame. It's up to you to figure out what you need to do to get
the right post in there.

OTOH, I don't know anything about the clamp that you have, so I have
to admit that it might be truly awful and that COULD be the cause, but
you need to keep in mind that it doesn't take much clamping force if
the seat post is the right size.

-
-----------------------------------------------
Jim Adney [email protected]
Madison, WI 53711 USA
-----------------------------------------------