My slide caliper sucks and doesn't measure fractions of a MM. I knew I needed a 26.something for my Peugeot build and went to Sheldon's seat post database to hopefully make an educated guesstimate on the size I need.
Anyways, I bought a 26.4. When I slide it in it is kinda difficult to get it in initially then it slides right in after the first 2 inches or so. The ears on the seat lug aren't crimped in at all but when the post is fully inserted I can move it back and forth ever so slightly. Is that an issue?
I think it will tighten just fine (I need a binder bolt) but again it will move the slightest lil bit way down in the tube. What say you? I've seen shims that only extended 2 inches into the frame so am I just being paranoid? Or should I pick up a 26.6? I don't like shims......Oh and it's supposedly 531 which makes me think it's just thinner further down the tube and therefore natural that a post could move a bit down in there.

Thanks,
Kelly D

I'm almost certain that 26.4 is the correct size.

The top of the seat tube is not butted, so it shouldn't be thinner further down.

Cool.....Thanks!

A properly fitting seat post will slide smoothly down, almost on its own, in a new bike/new seatpost situation. A tiny bit of wiggle should not be a problem if you have plenty of "ears" on the binder to clamp er down.

It is far more likely to be 26.4. Do you have corrosion in the seat tube?

Well I hobbled together a ghetto seat binder bolt and installed the post. It fits just fine and seems solid enough. Doesn't move a bit and I hardly tightened the bolt.......Now to find a better bolt and a new Brooks!