I've never heard of a weight based tire width rule. How does this work? Do riders have to weigh in before the race then get a tire check?
My local series doesn't have a "clydesdale" category, so no one is stepping on a scale. I cannot even imagine how complicated (and unnecessary) this would be to enforce.
At my series, everyone either races in their USAC category fields, or you can race in any Masters category up to your age (i.e. if you're 50 years old you can race in M45+ or M35+, but not in the M55+). We also have a separate field for single speed (zip tied SRAM shifters are allowed).