Ok a 12.3mm rotor is the maximum legal for a stock 17.5t right? 13mm rotors are available and I am sure some people do use them. What kind of advantage would they have? Why doesn't roar just make 13mm rotors legal for all classes to avoid people exploiting something that doesnt ever get checked except for at a nationals?

I think bigger rotor will give more torq and bit less rpm.

Our 13mm tuning rotor (photo) features an "identifiable groove on the shaft bevel to differentiate it from other Novak rotors." Of course, that requires someone to check for it.

Yes i noticed that the other day. It would be nice for motor manufacturers or roar to develop a standard so that oversize rotors can be easily identified. In your opinion novaktwo, would the 13mm in a stock motor make much of a difference?

I've done some testing with my tekin motors and thought the "oversized" rotors took away too much rpm for most tracks. 17.5's, with their lack of rpm, seem to operate best with the 12.3 to 12.5 rotors on all but the smallest tracks. I don't think most places bother to check because there really isn't much of a benefit. Roar just has to make a rule so that there can be no argument about "perceived" advantages.