Originally Posted by
Brian McGreevy
For even relatively small on-road tracks, you'll want to be between 3.5-3.7 FDR, depending on the timing your motor needs to run its best. I'd recommend a spur of between 86 and 92 teeth. Pinion sizes between 46 and 52 teeth.
+1
I've been running USGT (21.5T) for a while and a 3.5 FDR is great for fast corner speed, if I ran 3.7 to 4.0 then my car would accelerate too fast and tend to be more twitchy on corner exit.
I'm currently running a 3.3 FDR (48P @ 66/40) which is the sweet spot so I can drop the hammer throughout most corners without breaking loose and maximize top speed on the straights, I'd say I'm about 0.5 - 1.0 sec faster per lap than with a 3.5 FDR where our track average is around 15-17 second laps for most drivers in this class in blinky mode at my local club to give you an idea of what our track size is on an outdoor asphalt track with medium grip.
I'm running a Turnigy TrackStar 21.5T + 3Racing cooling fan and my motor temps come off around 130° after 12min mains.