Attention in the Paddock! Calling all C-Street Prepared!
#16
Drifting
I too was eyeing the new STR class, but to me the S2000 is going to be the car to have in that class. You could feasibly make the car STR & CSP legal (and reasonably competitive in both), just by switching wheels/tires between classes.
#19
Drifting
The biggest difference I know is the tires (obviously) - CSP allows "anything", which essentially equates to 275/35ZR15 Hoosier A6's. STR limits you to 255 "street tires", effectively being 255/45R15 Bridgestone RE11's (or one of the 2 or 3 competitors).
Other than that, without reading the fine print, it seems as though the suspension rules are pretty equatable. Neither allows much for engine mods, and you're probably best running a stock motor in either - but note, that due to the wording differences, STR would allow you to do an S2 motor swap.
#21
Drifting
You can get up to a 18" wide 15" wheel if you're so inclined . You see a lot of CSP guys running the Diamond wheels as they're cheap, reasonably light and strong.
#23
Drifting
P275/35ZR15 vs P275/45ZR16 for the max width of each. The big difference is the 15" wheel/tire is 23.0" in diameter, while the 16" is 25.6" in diameter. That means the 16" wheel/tire has 114% the gear ratio of the 15" wheel/tire. Thus, you would have more RPM at a given speed with the 15" wheel/tire - and theoretically more HP at that given speed. Not to mention, the 15" wheel and tire is typically lighter.
I've seen some guys pack both the 15's and the 16's (or 13's and 15's if their brakes are small enough), and then make their decision at the track to get the gearing right for the course.