I have a Trek 7500 FX. When I got it used, the seat post was obviously something that was swapped in after. Here is my question:

Does anybody know the size (diameter) of the seat post on a Trek 7500FX? I know you're thinking "Why don't you just go check it for yourself?"
Because I have it rigged perfectly with a seat post shim and 1 wrap of sandpaper. Plus my Allen head on the seat post is stripped out. I have to grip it with a pair of channel locks and tighten the hell out of it to get it to stay put. It took me forever to get it set just right and I'm afraid to take it out for fear of not getting it back just the way I had it. Kind of like when somebody else drives your car and they mess with the seat.....you can never find that perfect seat configuration ever again. I want to order a new post from Nashbar, but I don't know the size.

Can anybody help me out here?