wheels wont roll, wierd bone targeting

I have a rig involving four wheels and arms. The left arm seems to be targeting something non-exitistant or just an arbitrary location in space. I notice it when moving the root bone around which is the parent of the rig obviously.

I have started rigging the wheels to roll automatically upon moving the root bone around, but the suppose to be rotating bone is not doing anything. Could you please take a look to identify what the cause is?

Thanks a lotbot_share.blend (549 KB)

If you clear rotation, location and scale of the bones it will fix the problem. (ALT-R, ALT-G, ALT-S)

This is what your Transform panel should look like to get that wheel working:

http://s19.postimage.org/cesiqpng3/Capture.png

It can be easier in many cases just to use a driver but its up to you.