Ol Dan, for starters I recommend spreading the "ears" on the seat lug first. The way to tell is the slot between them is the same width from to to bottom. That will frequently round out the the seat tube and lug quite a bit.

Tubes are not always round, same with lugs. When heated they may conform to each other. As I showed in my picture above, the tubes frequently have bulged areas inside the lug from overheating when the seat stays are brazed on.

That's why trying to measure the inside diameter of the seat tube with a pair of calipers isn't accurate - the bulges can be 1/2" to 1" down from the top and generally in localized areas.

I start off with the largest socket that will fit into the top of the seat tube without any force. Sometimes I only need 1 socket to round out the seat tube and lug... Sometimes 2 or 3.

A few years ago I bought an early 70's all Campy Gitane Super Corsa. I adjusted the seat for the first ride and it slid down so I readjusted it. When I got home, something didn't look right. The seatpost was 25.8mm and should have been 26.4mm! It apparently came that way from the factory.

It took some work to get the tube round....

To answer your question about "spring back", I sneak up on the bore moving it out a slight bit at a time so the tube doesn't move that much with each size socket. That way the spring back isn't significant.

I use the word GENTLY because you could crack the lug and seat tube if you get carried away!



I use sockets because there easy to work with and the all thread can be used as a slide hammer to get them out. You could use a mandrel too.

Hope this helps...


verktyg

Chas.