Seatpost slippage

[cyberknight]

The seatpost on my giant retro mod keeps slipping :sad:
It has a factory fitted shim and no matter how tight i do the clamp up it slips , i did grease the post when i installed the new one that i made sure was the correct size as the original was single bolt that i can never get level .The seat can be nudged sideways too easily enough.
Take the grease off? carbon paste ? replace the seatpost clamp ? ( the last would be a shame as its the original once branded one )

 

[d8mok]

Measure the new Seatpost compared to the old one. Seatposts aren’t always true to size.

 

[ishaw]

Greasing a seat post, not sure that's doing you any favours. Yes, it may not get stuck but there's a reason for that

As above, seat post tolerances can be pretty vast. I've had a 27.2 post slot nicely into a 27.0 frame, and also posts that won't fit into the frame very much at all despite being the right size of the previous one. .

If you have the tools to measure both posts, see how far out the new one is diameter wise. If it's not, then clean the grease out.

Is it a cadex frame? I had one which I thought was a 30.0 post size but turned out it needed a 30.2, you could see/feel it had dropped a little during the ride.

 

[Imlach]

What's the frame? Carbon paste isn't a lasting solution, it may add enough bite to hold it but as it breaks down it will eventually start slipping again. I've had to replace seat clamps, to bolt type ones on 4 frames, but I'm also very fat. But it does sound like your new post is slightly under diameter. It's common and I've myself that problem with posts. The only fix for me was a stronger clamp or getting a different post.

I've also tried the various other ways, gritty stuff in grease and chalk and what not. No cigar, just to make sure you manage expectations with various pastes etc.

 

[jimo746]

Got a photo of the seat clamp/post/shim in position?

Interim fix could be using a strip of Coke/Beer can as a shim, but then that'd be a shim upon a shim (I assume you're still using the factory shim you mentioned?) which is not ideal longer term.

 

[cyberknight]

It's a giant compact road,this is the original post

 

[cyberknight]

Since this original post I have changed the seat post and clamp, the original frame clamp is for a 30.6 post with the frame shimmed for a 27.2 post
Original seat post clamp I'm guessing as it's once branded ,the threads do look worn

 

[Sir Neil d'Menture]

Got a photo of the seat clamp/post/shim in position?

Interim fix could be using a strip of Coke/Beer can as a shim, but then that'd be a shim upon a shim (I assume you're still using the factory shim you mentioned?) which is not ideal longer term.

That was mentioned, and rubbished, on a thread OP started on CycleChat.

 

[d8mok]

Remove the shim and fit the correct sized post.

Shims are a resolution for a problem that doesn’t exist. If the manufacturer fitted one to help with compliance I’d simply assume they don’t know how to build a comfy bike.

 

[Aech]

I take it the shim has a slit in it so it can compress with the clamp to grip the seat post ?

Just a thought is the gap in the shim big enough ? the shim could be closing up before it clamps down onto the seat post fully...