30.9 in 31.4?

[Nooch]

I might have asked this before, I can't remember for the life of me. My Corsa is without a seatmast, and the ID is roughly 31.4. A 31.6 thomson won't fit, and i'm currently running a 27.2 with a 31.4 shim, which is fine. But, I hate the shim.. such is life. My thinking was that a 30.9 would do the trick, but I want to make sure I'm not off in my thought process..

[kramnnim]

30.9 in a 31.4 would need a shim...?

[Nooch]

Originally Posted by kramnnim

30.9 in a 31.4 would need a shim...?

I guess that's the question -- is .5mm too much that it would slip, before i buy a post and try it for myself..

[kramnnim]

I don't think it would be good long term.

[icepick_trotsky]

Sounds like a job for a beer can shim.

How old is your Corsa? Mine takes a 30.9.

[Nooch]

Originally Posted by icepick_trotsky

Sounds like a job for a beer can shim.

How old is your Corsa? Mine takes a 30.9.

It's a Kelly Bedford built frame, so the newest/last of the corsa's, I believe. But I'd imagine all the tubesets were the same...?

[AngryScientist]

I'm not home to look, but my aluminum peg I think took a weirdo 31.0 post I think. If you need setback I have one sitting in the garage you can try if you want. Forget the brand but it's a carbon something or another

[hampco]

A good shop or a builder should be able to ream it to 31.6, if that's the size it should be. Maybe make sure that your Thomson is actually a 31.6 as seatposts have been known to be not the size advertised.

[Mark McM]

Originally Posted by Nooch

I guess that's the question -- is .5mm too much that it would slip, before i buy a post and try it for myself..

To answer your question directly - yes, 0.5 mm is too much to expect the seat tube/seatpost clamp to be able to squeeze down to. Take the advice of others, an investigate shimming or reaming (or finding an appropriately sized seat post).

[Nooch]

EH, I suppose I'll just leave the 27.2 shimmed then. It's just that one little thing that annoys me about an otherwise awesome bike..

[Nooch]

so, someone happened to have a 30.9 seatpost and I figured I'd give it a shot.

seatpost slid in, didn't have any sort of side to side movement before clamping, but this is how we were looking once clamped -- too much/indicative of being too small? I didn't want to risk it so went back to the shim/27.2 for the moment (of course cracking my 27.2 shim in the process... sigh...)

[oliver1850]

I have a new black 31.4 FSA zero setback post here. Probably have something 31 as well.

[merlincustom1]

Albert Bold can make you a custom post. He did a 29.4 for my Pegoretti.

[oldpotatoe]

Originally Posted by Nooch

so, someone happened to have a 30.9 seatpost and I figured I'd give it a shot.

seatpost slid in, didn't have any sort of side to side movement before clamping, but this is how we were looking once clamped -- too much/indicative of being too small? I didn't want to risk it so went back to the shim/27.2 for the moment (of course cracking my 27.2 shim in the process... sigh...)

Bad idea..get the correct seatpost or shim it to 27.2

[ltwtsculler91]

I'd say time to order a post, or maybe see if we can ream it out again to 31.6?

You can also just leave it as is, it did get you through 100mi on Sunday