[jhautz]

Use the BrianG speed caluculator and target 40mph. That should be plenty for the track. Not many nitros actually getting to those speeds.

I typically shoot for right around 38mph and that seems just about perfect to me.

with 4s on that motor in a buggy 20T should get you to about 38mph and 21T should get you to 40mph. Sounds like you are on the right track to me.