Originally Posted by microed

Tires are not the problem. It is more of an issue of getting the gear ratio down into the 3.5 to 4.0 FDR for a brushless setup without using non-Tamiya parts which is not allowed according to TCS rules. Of course you can run a silver can 540J in the gt3 class and gearing won't be an issue, but you will need to run against others chassis with 21.5 brushless motors. There is no way a 540J motor is anywhere near the speed of a 21.5, a 25.5 maybe, but not a 21.5.