I agree apex96 lots of testing. The reason I asked this is because its been an on going argument on here. I just want to know what formula they use to get on their ratio. You can go to a track one person may run good on 18 driver other may run good on a 17. I think its more about the kart set up, tire prep, and drivers ability more than a ratio is ratio. Its more about testing and what works for you.