I have been looking at the big fat tires on my old one-speed clunker that I use for close to home errands. I am thinking that with narrower tires it might even be a viable backup to my regular commuter bike in an emergency. Now with my good bike, I can go the the Mavic website to see what tire width ranges the rims will take. Is there some rule of thumb for minimum tire width on unknown rims? I am not trying to replace a 2.125" tire with a 23 mm tire, but maybe replacing a 2.125" 40 psi max tire with 1.6" 75 psi max street slicks. Is there a formula like 1.x times the inside width of the rim or width of rim plus x mm?
Thanks,
Raymond