Originally Posted by
aussierevo
I'm looking at gearing suggestions for 21.5 blindly. I run thunderpoercwith standard rotor on X-ray t4 with 73 spur and 39 pinion and temps of 65 degrees c in day. Timing at 40. Changing to torque rotor, thinking of starting at 74/38 fdr 3.71 timing 30. Running in heat of day so looking for good starting point so not to let the smoke out of the can. Appreciate any input.
Even though this is Paul's thread you should be good up to 82 degrees C so you could probably drop to a 3.6 fdr but I wouldn't run much more than the race time. Also on the higher turn motors you should keep the timing up pretty high to help get the top end of the motor. Here in the US running 25.5 VTA I'm geared anywhere from 3.50 to 3.70 depending on track and the temp outside. Running maxed out timing on the can. If your extremely worried about temps I'd start at like a 3.65 run it for length of your race and temp it and adjust from there.