[RoddyMcWolfenstein]

Building up a new frame and it appears the O.D. of the seat tube is between 32.2mm-32.6mm. That said, I am coming up empty on a seatpost clamp for it.

Most of what I see for sale is either 31.8mm or 34.9mm. Being that 31.8mm is pretty close to what i have, would it be feasible to use one of those on my bike?

 

[subsist]

What do you mean it is between 32.2mm and 32.6mm?

It is either one or the other, you should try and get an exact measurement.

You probably have a 31.8mm, are you measuring it with the seat clamp closed completely, if it is not closed it will not be pinching the tube to the correct size when measuring it.

 

[RoddyMcWolfenstein]

Its a brand new frame, its never had a clamp on it. It takes a 27.2mm post. I think its just a bulkier aluminum. I say 32.2-32.6 based on what my friend said he measured. Trying to get a more exact meaurement.

That being said, is it feasible to make a 31.8mm to fit my situation, or do I need to find some custom size?

 

[veteran_youth]

Assuming you haven't tried already, it's highly unlikely that you can make a 31.8 fit, and impossible to make it fit and function properly.

I think it is a Specialized specific size so you may want to try a Spec dealer.

 

[alvmech]

Hope my experience helps...
Had a carbon seatpost sized 27.2mm. Presuming most clamps sized 31.8mm would do the job, I went & bought a carbon clamp sized 31.8mm. Only realizing later, after looking under the existing clamp, which states 32.6mm. There was an outer shim at the clamp area which made the diameter larger (Probably this is needed for some carbon frames & not aluminum ones). Knowing the clamp was a few mm short, went ahead anyway to try the 31.8mm carbon clamp on the bike frame. After applying some carbon paste, I tighten the clamp with a torque of 3Nm & not 6.5Nm max as indicated on the new clamp (Didn't want to stress the clamp further). It held the seatpost tight, rigorously tested it further to see if there was any slippage, none whatsoever, it did the job! I suppose with a carbon clamp there is a certain amount of flex which allowed it. May not work for an aluminum clamp as that is stiffer. Btw my frame was a carbon too.