Originally Posted by
sciencemonster
Measuring the chainwheel c-c is about 88-89mm. According to Shelton, that's a 151 BCD. It's a '69 Comp, so I suppose that makes sense, but it means replacing the chainwheels is about impossible. I'd prefer to keep the original hubs rather than replace w/something modern and then have to coldset the frame. It seems a lot easier just to replace the cranks. But in doing research, it seems then that the BB axle would be too short.
Maybe I should just throw on a new derailler to get what I have to work smoother. I just don't like how it changes gears now. If I could get it to change smooth in the back, then I could stick with what I have.
My big concern with that, is buying old deraillers is expensive, and they don't seem to work much better than what I have, and I have no idea if whatever I buy will work with a 32T in back. RIght now I have a Svelte on a hanger as an extention, plugged into the hanger that is built in on the drop out. Pretty sketchy and it doesn't change any better than any other derailer I've tried.
I'd like to just try a good quality modern derailler and see if that fixes everything, but I have no idea what will work.
All very fustrating.
I believe the 69 Competition came with Simplex deraillers, worth round canning those. The Zeus crank will be virtually impossible to find chainrings for: I'm not sure there were even spares back in the day.
I assume you want to stick with friction shifting? I'd look for some friction Japanese deraillers on ebay, plenty of choices that would work well, long or short cage, depending on what size freewheel you want to run.
I recently picked up a brand new, generic Asian made triple for my wife's bike for around $40. on ebay, and a new, sealed Shimano triple bb from the LBS for $28. Everything should work fine with her 105 indexed bike I think.
With any drive train, getting the chain length right is the key to proper functioning. Should be just short enough to run in the large/large combo, though you wouldn't ride in that gear, right?