Gangrel

I was riding today and thought my knee wasn't extending all the way, but didn't think too much of it. Anyway, I get home and I'm eating dinner, look back to where my bike is resting and I realized the seat was level with the handlebars.
The dang thing has fallen a couple inches, and I forgot to mark it as I had intended when I first got it fit.

This happen to anyone else

~shadowfax~

Nope, but I do have a creak that the LBS cannot find.

biker7

I have a tip for you that will help. I too had a problem with slipping alloy seatposts on my Bianchi...the most recent being a Thomson post with a good reputation...lightly serrated to prevent slipping. The thing you don't want to do independent of any frame material...CF being the most tenuous...is overtighten the clamp. The best and least invasive solution I have found? Hairspray. Works great for all frame and seat post material combinations. Sounds funny doesn't it? But it works. A slipping seatpost is frustrating... kind of ruins a nice long ride. Remove your seat post and wipe out your seat tube and your seatpost with alcohol. Then take the seatpost and spray it with hairspray...a nice healthy coat...cheap stuff works best because it is the most tacky. Let the post dry for only a few seconds and then insert it straight down...no rotation down to the mark. Helps to premark your post with a bit of tape...also helps because you don't want to spray above the insertion line. Then torque your seat post bolt to spec and not an in-lb more. Think you will find it will hold nicely. No need to sand or ruin the finish on your nice seatpost. Also no need to spray inside the seat tube...I wouldn't. And will be able to remove the seatpost without diffiiculty.
HTH,
George

Gangrel

Interesting, I may try that. I'm going to take it to the shop tomorrow and freakin' mark it this time.

biker7

Its a common problem on all kind of bikes and materials. Most common mistake is overtorquing the seat tube clamp which can have big consequences. Many times removing all grease...you know not to grease a CF post anyway...will not solve the problem. I don't like the solution of inserting a shim in between the post and tube because it creates a stress riser...the intent but also can scar a post or cause failure. You want to increase the friction between surfaces without degrading the surfaces if possible. The least invasive method I know of that really solves the problem is common hairspray.
George

garysol1 

I keep a piece of electrical tape taped onto the post right where the seatpost enters the frame. While I am riding I can quickly glance at the tape and see if the tape has pushed up at all. If the frame has pushed the tape up I know that the post has slid. I did have issues with the CF post sliding on my R2.5 before I roughed it up with 500grit

Surferbruce

your seattube has a brass shim in there right?
it should have one which fits in the rear corner of the tube to prevent slipping.

Gangrel

I dont see where there is room to "fit" anything into the tube, so.. huh?

biker7

There are all kind of homebrew solutions to slipping seat posts. Different posts have different tolerances and clearances to different seat tubes. Sometimes too much clearance is the culprit....sometimes not.
George

Gangrel

well consider the soloist seatpost is teardrop shaped, so not all methods will work, I'm sure.

Cervelo

As some one said earlier there is a brass shim that comes with the the Soloist
to make the seat post fit properly. I have never seen one without it
unless they changed it this year. If you do not have one then your seat
post will slip and you could easily damage your frame and or seat post,
espescially if you have the carbon one. My Soloist seat post has never
slipped in at least 10,000 miles. With no hairspray or sanding
and just tightened to proper torque.

Note: I am only talking from experience about the aluminum Soloist, if you
have a carbon one I have no experience with those.

Surferbruce

hopefully this link works...it should have this in the seattube,
https://customercare.cervelo.com/est...px?id=7&page=1

Gangrel

Yes, that is in there.. however, I don't see how it prevents the post from slipping? Unless the bike was built improperly.

ed: Unless, I guess it is just there to fill in free space.. in which case I guess the post just slipped because the clamp was loose.

Surferbruce

grease your post and you seatpost binder bolt and crank it down.