|My car drives, but not straight.
The motors are on different power levels.
The wheels are not lined up properly (height).
The wheels may be bent.
Each pair of wheels has the same two wheels.
The gears are not lined up properly.
Mismatched motors, all Lego motors do not have exactly the same power level.
Bad: The bottom right gear in the photo is not lined up well, so the car always veers in that direction.