why does my seatpost slide down?

[LeonvT]

Change it to bolt on clamp. QR clamps are notoriously crappy... 

Thanks. I will look into that

[BMXER]

Tightern the seat clamp bolt till you hear a crack, then back off 1/8 of an inch.

 

Works wonders in procuring a new carbon post, ultimate motivation to upgrade.

[Jehosefat]

Had the same issue with my Big.Nine 500. Solved it by tightening up the quick release. You have to make it pretty damn tight but it sorts out the problem.

[Hairy]

Similar issue with my commuter bike. The carbon post I am currently using keeps slipping. ....even if you crank up the seat post clamp. It does not do this with my other alum posts though!

 

My final solution, seeing as it is my commuter after all, was to slide the rear lights bracket all the way down on the post and tightened this well. Have had no slipping issues yet.

 

Beware if you over torque the seapost clamp. ....they tend to strip route the bolt or clamp.....wrecked a couple before using the clamp as an aide.

[venom1]

Change the clamp (perhaps avoid the quick release clamps)

Clean the seatpost and seat tube

Carbon Paste

Use the correct torque

[karlito]

If there was grease on your seatpost and you cleaned it off there might still be grease inside your seat tube. 

 

So just shove a rag in there and clean it up as well.

[Martin PJ]

Quick release clamps are not very tight, even if you think it is. Posts slip because they are too small. If you put a small shim, it won't slip, maybe cut a sliver with coke can.

 

I agree with one of the other posters, if you keep shimming and it slips, check it if is not 30.9 post in a 31.6 hole. This happens to me once. The shim for this conversion is quite thick. At least two coke can thickness the whole way around the post.

[ABrooks]

Had the same problem a while back. Took the quick release clamp off to have a closer look at it and found it to be cracked. I bought a new seatpost clamp (quick release type) and put a few drops of chain lube on the moving parts of the quick release. The seatpost has stopped slipping since replacing the clamp and the lube helps to easily adjust the clamp if necessary.

[gummibear]

Is it a dropper post?

     

[Sidersky]

Thanks. I will look into that

Had the same issue way back when, made the same change, problem solved. And it takes a few seconds longer to get out an allen key as opposed to the quick release clamp so well worth it, trust me.

[LeonvT]

Quick release clamps are not very tight, even if you think it is. Posts slip because they are too small. If you put a small shim, it won't slip, maybe cut a sliver with coke can.

 

I agree with one of the other posters, if you keep shimming and it slips, check it if is not 30.9 post in a 31.6 hole. This happens to me once. The shim for this conversion is quite thick. At least two coke can thickness the whole way around the post.

 

Don't think that I will be able to get a sliver of coke can in there. 

It is the original post that came with the bike when I bought it new and it worked well for a couple of years.

[LeonvT]

If there was grease on your seatpost and you cleaned it off there might still be grease inside your seat tube. 

 

So just shove a rag in there and clean it up as well.

 

I tried that. not difference 

[LeonvT]

Had the same issue with my Big.Nine 500. Solved it by tightening up the quick release. You have to make it pretty damn tight but it sorts out the problem.

interesting...I am a bit worried of over tightening it and don't think I can do much more than what I already have.

[BaGearA]

interesting...I am a bit worried of over tightening it and don't think I can do much more than what I already have.

Don't tighten too much then the dropper may start to have problems extending.

 

Put A liberal amount of fibre grip/paste on the seat post and reinstall. That stuff works wonders.

[SwissVan]

I wish people would pay attention when reading threads, or maybe they don't read....

 

To the OP, how tight is the quick release when you close it?

If you can still close it with thumb pressure quite easily try tighten it a little more.

It also helps to clean and lubricate the quick release lever moving bits so they can slide over each other easily.

[Kalahari Vegmot]

Use Installation compound/anti slip paste. Sold in a 5ml sachet at your lbs. Had the same problem as you with a qr clamp. Works perfect now even with the qr clamp. I've got an alu seatpost and frame btw