Originally Posted by wingracer

There are a few different theories on why motor position matters and I'll touch on them but the simple answer is to always use the biggest spur/pinion combo that will fit in the car (and gives the right rollout of course) to get the motor as far forward as possible. It just feels so much better. As to why...

1. Unlike nearly all other vehicles, the motor is rigidly mounted to the rear axle so it is unsprung weight. However, it is not mounted centered directly over the axle, it's between the axle and the suspension pivot so there is a motion ratio involved. This means that some percentage of motor weight is unsprung and some is sprung. The closer the motor is to that pivot and farther from the rear axle, the less unsprung weight/more sprung weight. This is a good thing.

2. Torque from the motor (accelerating) or applied to the motor (braking) acts directly on the suspension. Pan cars are actually opposite from most cars in that the motor tries to climb the spur under acceleration, lifting the rear while the spur pushes down on the motor under braking, causing it to squat. My theory is that the closer the motor is to the pivot point, the less severe these forces will be. I could be totally wrong about that but on track feel seems to back it up.