I just picked up a bantam complete handle to use the knobs. When my Shimano knobs are tightened down the screw stops and the knobs still spin freely. When I put the Shimano knobs on my zillion and I tighten the screw down the knobs won't spin. I have to back the screw off for them to spin without resistance, but then the screw is not tight. Am I doing something wrong? Is this where the shims come in? Not really seeing how that would help. Where can I purchase these shims if that is what I need to do?