Originally Posted by Just Riding

A few months ago I picked up a Trek 970 frame. It had a crank and derailleurs, and also a stuck seat post. It was pretty beat up, but I thought it would be a good winter project to build it into an errand bike.

I ended up cutting the seat post out after other methods failed. The seat post that came out was marked 27.2mm. When I tried to put another 27.2 seat post in, I could only insert it about 3 inches. I tried a 27.0, and that would go in about 4 inches. I tried a 26.6 and that would go all the way down, but it was fairly loose.

I got a flex-hone and honed the seat tube. The seat tube is nice and clean now, but the inside dimensions were essentially unchanged. I called the flex-hone manufacturer, and their tech support basically said that a flex hone will give you a nice surface finish, but won't remove much material.

I don't understand what is going on with the seat tube. I can't see any dents in it. I measured the outside with calipers and it doesn't seem to be ovalized. I have no idea though, of what might have been done to this seat tube in its past lives.

The frame is lugged 4130 chro-moly, and based on colors is apparently a 1990 model. The seat tube lug clamps nicely around a 27.2mm seat post.

I figure one option is to use a 26.8mm seat post that I shim out to 27.2mm at the top. The other option is to have the seat tube reamed to 27.2mm, but before I look for someone to do that I thought it might make sense to find out what the original seat post size was.

The local Trek dealers weren't able to help with information on the correct seat post size, and when I emailed Trek I got a polite brush-off.

Does anyone know what size seat post this frame came with? Also, are there any reasons why this frame shouldn't be reamed to 27.2mm?