Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I got a Cannondale Quick1 2010, with the seatpost made with aluminium carbon-wrapped.

The problem is that the seatpost tends to slide downwards, even if I squeeze a lot the snap ring; if the ground is uneven the seatpost slips completely.

Is there a way to solve this problem?

Many thanks.

share|improve this question
1  
Quick release seat clamps never work for me as I'm a big guy and unless I use a allen bolt type I can never get them tight enough. As it's integrated into the bike you might have problems fixing it. Go back to the shop and have them check things out for you. –  Chef Flambe Feb 15 '12 at 6:16
add comment

5 Answers

I had this problem and looked into it at the time and the carbon gripping compound as mentioned ny Nick H, is the way to go.

But there was also a "cheap a&%e" solution of using either hairspray or the spray-on adhesive for sticking paper together. You spray some on the seatpost and clamp it tight. The light glue in the spray provides enough grip to keep the post in place. But its not so sticky that it stops the seatpost from being adjusted later on (and it can be washed off)

share|improve this answer
add comment

You can always go to a hardware store and get a stainless steel spiral screw hose clamp. Wrap the post with a couple of wraps of rubber from an old inner tube, then apply the clamp, tight against the existing collar. Tighten the heck out of it.

Always a risk you could crush a hollow post, I suppose, but once you get that thing on the post isn't going to slip down.

share|improve this answer
add comment

If the carbon gripping stuff does not work. Try a collar with two bolts. These are typically used for mountain bikes. Obviously you need to ensure it is the correct size for your frame.

I had the same problem mating my carbon cyclocross frame to my carbon seat-post. Carbon gripping compound helped and seemed like the solution, but when it mattered (that is during the race) the seat-post slipped.

share|improve this answer
    
The collar clamp of the Cannondale Quick 1 is very uncommon (as you can see) and cannot be replaced with a different type of clamp. However I solved the problem with the carbon gripping gel. –  Sam Qasbah Feb 28 '12 at 16:41
add comment

I have never used carbon frames or components, but I've had similar issues with aluminum posts in aluminum mountain bike frames. In all cases the clamp was a hand tightened quick release type. I also helped friends with this issue, some of them had carbon frames or seat posts. Possible causes and correction applied where as follows:

Clamp is not providing enough clamping force. Adjust the clamp. Almost always this kind of clamp has some quick release lever in one side, and a corresponding bolt or nut in the opposite side, tighten it a little bit at a time until problem disappears.

Seatpost or inside the seat tube is dirty or oily. Debris, sand, mud, oil or even water between seat tube and seat post will create this kind of problem, also accelerating wear of both even when no apparent slippage occurs. Clean both and make sure they are reasonably dry before putting them back together. How does all the stuff get in there? mainly the rear wheel trows it, it sticks to the seatpost and then, during cleanup it runs down into the seat tube. Some frames are more prone than others to collect dust. Shall this be the case, there are commercially available neoprene or rubber protections that seal the clamp area, but on the cheap you can use scraps from old inner tubes.

The quick release lever is producing too much friction: due to dirt and/or damage or wear, the quick release may be developing too much friction, giving the false feel of tightening, but the force you excerpt is being wasted. Inspect the clamp and be sure it is not dirty or deformed, specially around the quick release pivot. Friction surfaces of the quick release and their counterparts shall be clean, smooth and dent free. Some clamps have a plastic, teflon or steel "cushion" that help these friction surfaces slide. This must be well shaped and clean. The friction surface of the quick release lever can be lubed with oil or light grease. That also helps reducing the force required to securely tighten the seat post. Dents and small deformations can be sanded down and polished with very fine grit sand paper.

There is dirt caught between the clamp and the neck of the seat tube: Dirt or other materials caught in there can also prevent clamp force to properly tighten the seat tube. Clean it, the the inside of the clamp and remove any stickers or loose paint. (Special attention with repainted frames here) The inner surface of the clamp can also be lubed and it helps, but very little.

Clamp is misaligned: The seat tube has a cut part in the neck, this should be aligned with the clamp's gap (Unless some weird manufacturer says otherwise). Check alignment, special attention if the clamp is an aftermarket one.

Wear: If your problem has been happening for a long time, chances are the seatpost or even the inner seat tube is worn out, thus having too much "play" between them and being too much flex for the seat tube to take up, so tightening it is not effective. To be sure seat post and seat tube must be measured with a precision caliper. Shall wear be the problem, hopefully changing your seat post is enough to solve the problem.

Final considerations: Never use excessive force to tighten the seatpost (or any other component), specially with carbon components, you'll cause too much stress and reduce the time to failure of the component.

share|improve this answer
add comment

Your local bike shop should be able to sell you some carbon gripping compound, for example Finish Line Fiber Grip. Other similar brands are available!

I've no idea what the seatpost clamp is on your bike but I'm always suspicious of ones that are hand tightened. I have 2 bikes with carbon seatposts & Ali frames, I use Salsa clamps that require an allen key & I don't experience any slippage.

share|improve this answer
    
Well, I've tested the carbon gripping compound, and I solved the problem. Many thanks. –  Sam Qasbah Feb 28 '12 at 16:23
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.