Chipmunk Physics

Hello slembke,
SimpleMotor seems not working correct on the left wheel.

I have tried to port this Box2D sample:
http://www.youtube.com/watch?v=ZALCNpHApro

to Chipmunk => I using the Chipmunk4PB wrapper:
http://youtu.be/STuQEyx_8Ts
Please watch to both wheels, the left one seems to hve not so perfect working as the right wheel.
Can I improve it? Or is there a better way to simulate it (I use cpSimpleMotor).

The motor looks like it's working fine, it just the spacing on the wheel or something.

What I would do is attach the wheels to the static body using 0 length springs instead of a pivot joint. Then move them a little closer to the curve. That way when a ball squishes between the floor and the wheel, the spring will push the wheel down onto the ball and keep it in contact better.