Interesting Dave. I have also found a bit of stuff about how those numbers can be manipulated, but it also looks like there are a lot of amateur series in the US that state a minimum UTGQ requirement for the tyres:
2014/2015 Street Tires (...actually it's 200 treadwear!) - evolutionm.net
We could make it the "180 Class" - which could also mean we tend to spend a lot of time pointing backwards...
