seat post slipping

I’ve put on my thomson seatpost (thanks dave) tightend the seat binders as much as possible but it still slips slightly. Is there any way i can secure it more?

ps it is the correct size.

Sounds like the top of the seat tube is flared a bit then. Make sure the seat collar isn’t cracking.

You could put a washer on the bolt to tighten it down more, but personally I’d look into why its happening to start with.

Have you measured the seattube inner diameter with verniers?

You could upsize the post by 0.2mm or source a shim (or cut up an aluminium can).

If the binder is bottoming out a washer will help, but if the seatlug ears are contacting or the seattube gap has closed, then it won’t change.

As snowflake said, figure out why it won’t clamp properly first, then decide on a solution to save future problems.

I’ve measured it, it’s 26.6mm.

The seattube gap is closed and the seatpost still moves slightly.
I might try cutting up a coke can.

thanks i will let u guys know if it works.


Though if it was tightened as much as possible, flaring or not, you need a larger seatpost I would say. I’ve never done any damage shimming things temporarily though (or permanently…).



if all else fails, talk to your local shop or frame builder about reaming the seat tube to take the next size.
if it can be done without taking too much material away, that could be your next move.

Sounds likely

After putting some cut up can around the seatpost it seems alot more secure, i wont know forsure untill ride it tomorrow but it seems alright.

Thanks for the advice everyone.