I am new to bike riding and am rebuilding a late 70s/early 80s Dawes from CL for an exercise bike. It came with Mavic GP 4 rims & very punky sew-ups. The only markings on them that I could find say "Hutchinson S". I was able to get a Conti Sport Contact 700C (28 x 1 3/8 x 1 5/8) between the stays and in the right place for the brakes (yeah for steel!) but the front derailleur assembly hits.
I already have a set of Mavic CXP22s & I'd like to use them, with a fairly fat tire. They take up 32mm tires, I believe. Since I don't know what size the current tires are, how do I figure out how big I can go . . . short of going to the LBS and trying on wheels & tires? Sorry if this is a dumb question.