My ol’ Big Top has a Thomson layback post. And it never stays put – doesn’t twist at all, but gradually lowers over a ride. Replaced the Yeti clamp with a Salsa clamp (QR), made no difference. Now tried the bolt up Kenesis clamp that came with my Tripster, done up tight as I dare.. put some electrical tape round to mark where the post was, by the end of a short ride round QECP the tape was mangled down inside the seat tube, so about a 20mm drop there. Had some carbon paste in there too. I’ve got a Thomson clamp looking pretty on the Tripster.. worth trying?
or is there a layback post worth splashing out on that’ll be a better fit than the Thomson?

or is there a layback post worth splashing out on that’ll be a better fit than the Thomson

I just won a little bet with myself that this thread would have some Thomson content.

Pretty much any other post will be better

that gritty carbon paste/grease might hold it

I had a Thomson Layback on my London road for years and it didn’t move once. Even with the over reamed seat tube.

Have brand x carbon one now, shimmed and it was moving for a while, even with carbon paste. I’ve since scuffed up the inside of the shim with a file and added more carbon paste and it seems ok now.

How much slop is there between the frame and seatpost when the clamp is undone?
It is possible to make quite a neat shim from aluminium drinks can.

Pretty much any other post will be better

Interesting! Probably just see what 30.9s I have in the garage and give one a go. Have tried carbon paste.

How much slop is there between the frame and seatpost when the clamp is undone?

None really, it feels like a good fit. Maybe I’ve just put on too much weight 😢