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Seat Post Slipping - Seat Post Clamp Question



 
 
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  #1  
Old April 20th 05, 03:40 AM
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Default 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 crap. 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

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  #3  
Old April 20th 05, 05:30 AM
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Thanks for the note, but this is not a quick-release clamp.

Regards,

Eric

  #4  
Old April 20th 05, 06:16 AM
Leo Lichtman
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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?


  #5  
Old April 20th 05, 11:56 AM
catzz66
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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.
  #7  
Old April 20th 05, 06:32 PM
Donald Gillies
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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
  #9  
Old April 21st 05, 06:03 AM
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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).

  #10  
Old April 21st 05, 02:42 PM
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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.

 




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