Here's a gearing calculator that'll get you in the ball park. You'll just need to knowyour tires diameter and transmission ratio; then you can play with the spur and pinion numbers to see what would be a good starting point. Then check the temps after running a pack, if you can't keep your finger on the motor for at least 5 seconds, you'll want to drop down a tooth or 2 on the pinion.


Gear wizard calulator