Originally Posted by bikemig

There are a lot of higher end bikes from the 70s with a remarkable amount--at least by modern standards--of clearance for tires. If you want something as fat as a gravel bike, you likely will have to do a 650b conversion (and you may have trouble sourcing brakes that can reach). 700 x 32c-35c (and sometimes a 38c) are not difficult to fit. My 70s Fuji Finest takes a 32c with room for fenders. I have a 70s Mercier 300 that takes 32c tires easily. Your best for a bike with good clearance is likely one that was designed for centerpull brakes and 27 inch tires. The early 70s Raleigh Competitions may be at one end of the bell curve given the elegant (and thin) fork crown and relatively thin chain stays, though. ...