Rules?
if you are a
Serious Collector/Stickler - lots of rules
Casual Collector/ rider - some rules
Average Joe cyclist - no rules
'I saw a movie bike' rider = crazy rules
Hardcore cyclist/adventurer - probably not strictly C&V, but not always
.
So, the correct answer is = It Depends. On you!
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Vintage, modern, e-road. It is a big cycling universe.