Originally Posted by
Andrew F 
I had a simular problem on a 40 year old frame. I ended up cutting a shim out of a thin alum. beer can. Can't see it and it works perfectly.
I may have to try this! How big of a piece did you cut? Did you lube the aluminum? I can imagine that pressing aluminum so tightly between two pieces of steel would eventually cause it to weld itself into place if you didn't.
I cut a band about 2.5" wide by 3", it wrapped about 3/4 of the way around the post. Lightly greased all surfaces, inserted and tightened the clamp. Worked perfectly. I did this on a Raleigh Sport with a steel post.