[Top Down]

I have seven Pioneer Legends. Looking from behind as they disappear down the straight:

Two are totally neutral under braking, stopping in a straight line.
One steps slightly to the right.
Three step slightly to the left.
One steps forty-five degrees to the left. 

As they disappear down the straight the sidewinder gear is on the left.

The only difference I can determine is the gearing on the last car is a bit tighter than the other six - but there is no way to adjust the motor and axle shaft positions to ease the gearing.

Any ideas anyone? 

All have totally stock running gear, with all tyres trued as near as possible to the same diameter. I know they're mass produced and there will be variations but I'd really like to dial out that massive step-out on the seventh car if at all possible.