[ksafin]

6 wheel drive.
you're doing it wrong.

but on a more serious note:
It's very weird how you did your 6 wheel drive; it looks like you leveled the wheels all out evenly?

Middle wheel should be ever so slightly lower so it can grip the floor and provide the actual movement by a motor, back and front wheels should be dead. Wither front or back will touch the floor depending on movement, so no more than 4 wheels will be on the floor at all times (middle and either front or back).