Question :Italian Racing Bike 650B conversion?
 

I recently purchased a Rossin SLX frame , as I ponder build possibilities I am thinking about 650B because I know the frame in all likelihood wont permit anything larger than 700x28. Has anyone converted an older Italian bike to 650B if so what are your thoughts on doing so ?

Thanks

If it counts, I converted a non-Italian Bianchi a few years ago. That project is overdue for an update: https://www.bikeforums.net/classic-v...thread-872218/

I think it can be a great way to mix the lively feel of a racing bike with the plush comfort of wider tires. :thumb:

There's nothing peculiar or different about an Italian bike than any other vintage bike when it comes to a 650b conversion. The main thing is you really want to be able to fit at least a 38c tire to make it worth your while. Also if much smaller than that, the bottom bracket height will get smaller and this may be an issue. The overall diameter of 650b x 38c is close to 700 x 23c.

This is a good description of what you should be thinking about before doing a conversion:

https://www.bikeman.com/bikeman-blog...sion-guidlines

Without pictures, I'll assume your SLX Rossin has typical Italian geometry from the 80's, which means short chainstays and forks made for short reach brakes. I highly doubt a 650b x 38 tire will fit with much clearance at all, if any. The only way to know for sure is to do a fit check.

Post pix showing tire clearance in the chainstays and fork from different angles and I could do a more complete assessment.

What was just written and wrong front end geometry will probably be all wrong for the exchange

Agree with the two experts above, but FWIW my wife likes her steel LeMond with 650x32b Confrerie (https://www.xxcycle.com/tyre-hutchin...0-b-ts,,en.php) but she was a never road biker used to mtb tires and soft seats. Much better for her than the 700x23s that were on there when we picked it up. Made the road bike rideable for her. 165 cranks on that though, and smooth easy drifting around corners, BB height could be an issue for some.

I did an 80s Benotto 2000 that took 38s fine, maybe a little low of bb. I've currently set up my oversized Centur-elli with 650b wheels. It would not take the 38s and I've put 35c Michelin Wildrunners on it. The bb is argueably too low, ~255mm.

gugie I do not have a set of wheels to test fit but I took some measurements of the fork and the chain stay widths and I Think the bike should accomodate 650bx38 without too many issues . Yes the chain stays are short but the bike has horizontal drop outs. I measured the stays at 419mm long

See the photos of the measurements of the fork width and stay width

https://i.ibb.co/9GGXsc6/IMG-7348.jpg
https://i.ibb.co/FbxZJ3W/IMG-7349.jpg

I'm putting together a Bridgestone 450 conversion, with similar clearance at the chain stays.

I went with 35mm tires, because my wheelset is a bargain basement deal, so I want some leeway for wonkyness and hopefully some plastic fenders.

Michelin Wild Run'r Tire - 27.5 x 1.4

I appreciate that , I am considering a set of the Pacenti 650 B wheels as they seem to be well regarded still sorting this out though as I've not done a conversion like this before. I just know I really don't want to ride 23 or 25mm tires as I like a plush ride for the sake of comfort