Hi folks,

Life has kept me away from bike projects awhile, but I'm thinking about converting a cosmetically ratty, structurally OK Raleigh International ('74) frame to 650B with moderately wide tires. I've measured it carefully: plenty of clearance between the fork blades under crown (45 mm +), but not so great between the round, non-indented chainstays behind the BB. To calculate what might be required, I measured some Pasela 35 mm tires mounted to 23 mm 700C rims, and find that the max. width of tire is at about 338 mm from axle. The frame has only 34 mm clear between stays at that distance from the middle of the rear dropouts (long Campagnolo type). I figured that, roughly, a 650B wheel, having BSD 38 mm less than a 700C, has maximum tire width at about 319 mm, where the frame has about 41 mm clearance between the stays.

Does that sound about right? If anyone with a set of, say, 42 mm wide tires mounted on reasonably wide (23 mm or more) rims would kindly measure theirs to confirm, I would appreciate the favor.

Ideally, I'd like to be able to mount and fender 42 mm wide tires. I've read about people "re-forming" chainstays somewhat, and am not opposed to paying a professional framemaker to do that, if it will solve the problem. I plan on several "fixes" and other changes too, like braze-on pivot bosses for centerpulls (no going back to 700C).



The black marks on the right chainstay are where I figure the max tire widths for 700C and 650B might be.

And for more general information, here's the original 2009 BF threadlet on this frame, with some more photos:
http://www.bikeforums.net/classic-vi...d-raleigh.html

Sorry, I find that I've never taken a decent set of photos myself. And I apologize for the "attachment" below -- having forgotten how to post photos from Flickr, I did this, and can't find a way to undo it.