gettin rid of the steerin servo wont work. if you get a bump big enough it can send the whole car in a diff direction. i dunno if this would would work but here it goes:
In the jet powered cars they make the wheels out of aluminum becausethe rubber ones cant handle the rpms. so you might be able to get aluminum wheels and just hook the engine up directly to the driving wheels. the only problem i foresee is getting grip with the aluminum wheels