I actually don't remember the exact pinions I made the mount to fit but I think the furthest you could move the motor back in the pod was with around a 20/96 - In Mod, we never run a smaller spur because of the ratios we need to run. I would like to run 100's but with that and the tire size we run the spur is full of tire foam after a run, 96 is the max you really can run. Also, we usually try to get the motor further forward in the pod rather than right on the axle...