>>1026027A road bike won't have clearance for cross tyres, even moreso with old bikes in my experience. Pic related is my early 90's road bike, it doesn't comfortably clear 25c's and I'm currently running some NOS 20c tyres from the 90's on it. Go to the co-op with a tape measure and check out the clearances at the chainstays, you might find an old CX frame.
