Seat post slip

[BJMcC]

Hi, My seat post is slipping quite a bit. How do I tell if I have the right sized seat post for the frame? I bought the bike second hand, so I'm not sure if it's the original seat post. It seems to be reasonably tight when I remove the quick release clamp and move it up and down. I have the clamp very tight and it still drops after a ride.

[find_bruce]

Now is a good time to check for cracks around the seat post clamp.

An easy fix is a drink can shim around the post

[Bentnose]

What bike is it, someone might know what size it is meant to be? Is it a carbon post? I had an issue on my MTB that was alu post and steel bike, a drink cam shim fixed that but it ended up cold welding itself to the frame because I left it too long between greasings. My road bike used to drop its carbon post in the carbon frame 10-15cm a ride, I ended up buying a new alu post and a clamp that was .2mm smaller than the one that came with it (it was an odd size), that was the only thing that could fix it.

[mikgit]

yeah what frame, what seatpost. I had a Manitou frame where the seatpost (Manitou/Ringle) would slip no matter what.
My current FS bike, carbon frame aluminium post was fine with the stock seatclamp, but when I switched to a QR clamp would slip a lot, carbon past helped a lot but it would still slip like 1-2 cm over a ride.

[trailgumby]

1-2cm during a ride would blow up my knees. I use carbon paste. No problems with slippage.

I only use a QR collar on the alloy-framed bike I share with my son. It's a Surly collar - quite a long lever and excellent locking geometry. Bolt-up collar on all the other frames, tightened to recommended torque.

[BJMcC]

Thanks for the responses. Its a Scott racing comp AL Evo 2, however there are no markings on the aluminium seat post. I just put in a drink can shim and I'll see how that goes. I'll be mindful not to let it coldweld itself to the frame. Failing that, I think the carbon paste is the next option.

[mikgit]

1-2cm during a ride would blow up my knees. I use carbon paste. No problems with slippage.

I only use a QR collar on the alloy-framed bike I share with my son. It's a Surly collar - quite a long lever and excellent locking geometry. Bolt-up collar on all the other frames, tightened to recommended torque.

Ha yeah doesn't blow me up on say a 1 hour ride, but I notice it. Usually the last 10 or so km of a ride is mostly DH so not such an issue. Went back to a bolt up clamp when I put on a dropper.