im just starting to get into racing, and i heard this talk of all of this and i was like wow, this stuff is serious, i thought you just change the pinion/spur and thats it. apparently theres alot more to it!
so how do i know my "IDR" then? i have a Corally RDX PHI. also, the higher the FDR im guessing it is the more revolutions of the tire per pinion revolution? or something along those lines.