I changed the chain rings on my bike recently. I put a 47T inner ring on in place of the 42T that was on it. The thing is, it is very close to the chain stay (~1mm) and if the frame flexes (accelerating, cornering, etc) that ring will scrape the chain stay. Yes, the bike has a very tight rear triangle.
Is there any way to shim the spindle-crank interface to move the rings outboard a bit. I did some calculations and a 0.004" shim will move the rings 0.125" outboard. I'm sure that would do the job.
I tried a copper shim but it is too soft. It extrudes out of the way when crank is tightened. Should I use aluminum foil, stainless steel shim stock or what? Does anyone make a pre-formed shim for this? How do you hold the shim in place as the crank is installed?
Is shimming the wrong way to go with this problem?