Seatpost slip

Quoted post said:

Originally posted by Burns
This question is a little ridiculous. It's been nagging at me for a while. I ride a Trek 8500 with
the typical Bontrager seat post and quick release collar. Over time (30min of riding on or off road)
I find seatpost slipping back into the seat tube. I've tried tightening the quick release, but i'm
at the point where i'm afraid to damage something. How hard can you tighten it down? In
non-scientific terms: enough to bench press 150lbs, 100lbs, 50lbs, 25lbs?

I've even removed the grease in the seat tube (previously there to keep out water) to see if that
helps. The Bontrager seat post has tiny horizontal grooves that I figured would "catch" better
ungreased. This does not help.

I bought the bike from a guy who never rode it. It did have some aftermarket parts. Perhaps this
seatpost size just isn't correct? How could I determine that?

Thank you in advance.

Burns

Calipers that measure the inside and outside diameter should be accurate enough.
The frame should have a specification from Trek.
However, you should measure it to see if it meets specifications.
Look at the top of the seat tube in the frame to see if the vertical slot is all the way closed. If it is, the seat post is too small.
Believe it or not, this may just a matter of tightening the QR even more. If the inside of the seat tube was cleanly reamed and properly greased, it may be quite slick.
http://www.parktool.com/repair_help/torque.shtml
Says "Seat post binder Campagnolo 36-60 inch-pounds"
Make sure there is clean grease on the threads of the fastener.

Unless your 8500 is rather old, it's most likely a 27.2mm seatpost (if it was very recent, it might
be 31.6). The size will be stamped on the outside of the seatpost; if it says 26.8 or 27.0, then the
chances of it being the incorrect size are rather high.

Most likely the seatpost is the original one though, as Bontrager would be the normal spec. Could be
that it's marginally undersized; best bet would be to bring it to a shop and have them check to see
if another post of the same size might be a bit tighter fit.

--Mike-- Chain Reaction Bicycles chainreactionbicycles.comchainreactionbicycles.comOpen ↗

"Burns" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

This question is a little ridiculous. It's been nagging at me for a

while.

Quoted message said:

I ride a Trek 8500 with the typical Bontrager seat post and quick release collar. Over time (30min
of riding on or off road) I find seatpost

slipping

Quoted message said:

back into the seat tube. I've tried tightening the quick release, but i'm at the point where i'm
afraid to damage something. How hard can you

tighten

Quoted message said:

it down? In non-scientific terms: enough to bench press 150lbs, 100lbs, 50lbs, 25lbs?

I've even removed the grease in the seat tube (previously there to keep

out

Quoted message said:

water) to see if that helps. The Bontrager seat post has tiny horizontal grooves that I figured
would "catch" better ungreased. This does not

help.

Quoted message said:

I bought the bike from a guy who never rode it. It did have some aftermarket parts. Perhaps this
seatpost size just isn't correct? How could I determine that?

Thank you in advance.

Burns

Burns said:

This question is a little ridiculous. It's been nagging at me for a while. I ride a Trek 8500 with
the typical Bontrager seat post and quick release collar. Over time (30min of riding on or off
road) I find seatpost slipping back into the seat tube. I've tried tightening the quick release,
but i'm at the point where i'm afraid to damage something. How hard can you tighten it down? In
non-scientific terms: enough to bench press 150lbs, 100lbs, 50lbs, 25lbs?

I've even removed the grease in the seat tube (previously there to keep out water) to see if that
helps. The Bontrager seat post has tiny horizontal grooves that I figured would "catch" better
ungreased. This does not help.

I bought the bike from a guy who never rode it. It did have some aftermarket parts. Perhaps this
seatpost size just isn't correct? How could I determine that?

Lubricate the cam of the quick release.

If it still slips, pull out the seatpost and write us with the size stamped just below the limit
line. Someone here will know the right size for your bike.

--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Burns-<< This question is a little ridiculous. It's been nagging at me for a while.

Quoted message said:

I ride a Trek 8500 with the typical Bontrager seat post and quick release collar >><BR><BR>

If it is the correct size, go to a bike shop that has a knurling tool, that can make some little
grooves in the seatpost effectively making it a wee bit larger-

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

"Burns" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

This question is a little ridiculous. It's been nagging at me for a

while.

Quoted message said:

I ride a Trek 8500 with the typical Bontrager seat post and quick release collar. Over time (30min
of riding on or off road) I find seatpost

slipping

Quoted message said:

back into the seat tube. I've tried tightening the quick release, but i'm at the point where i'm
afraid to damage something. How hard can you

tighten

Quoted message said:

it down? In non-scientific terms: enough to bench press 150lbs, 100lbs, 50lbs, 25lbs? Thank you in
advance.

Burns

I had a similar problem on my Gary Fisher. The seatpost QR clamp had an exposed cam design and there
was a piece of nylon (plastic) between the cam and the collar body, presumably to lubricate the
interface. My post would slip down maybe 1/2" in a 30km off-road ride..very frustrating. I had some
paint in the seat tubeso I removed all of that with some emery cloth and I removed the plastic piece
and greased the interface instead and this improved things considerably, but didn't really cure it.
I was closing the lever so hard I swore it was going to break off in my hand! I eventually switched
to a better quality bolt-type collar and my problem disappeared.

HTH,

Scott..

Quoted message said:

I was closing the lever so hard I swore it was going to break off in my hand! I eventually
switched to a better quality bolt-type collar and my problem disappeared.

HTH,

Scott..

thank you (to all)

i think that might be the way to go. seatpost is the right size. i think i'll switch collars.

no kidding about breaking off. after adjusting for the third time on hour long rides i'd be so
frustrated i push like i was a Strongman competitor on those ESPN2 shows.

Burns