Bounding Box info.

Can anyone point me in the direction of background info on the principles controlling generation of the bounding box of an object, please?

I've built a car, made up of various sculptie/prim components, which appears to hover 100mm or so above the surface I rez it on and, even if I move it down using edit so that the wheels touch the surface, when I make it physical it bobs back up.

I turned on Bounding Boxes in Info Display - the only way I know of to see the outline of the actual containment, but none of the individual component bounding boxes appear to project down low enough to cause the complete car to rest in mid air and I'm at a loss as to why it is happening. The bounding boxes for the components show green (root prim as yellow) whereas the overall box which appears to dictate the object height above the ground shows as orange.

Any help/info would be much appreciated.

The physics engine does leave a gap of - you guessed it - 100mm. It's one of those SL oddities you just have to live with.

Make the wheels flexible, but very stiff, and they will become phantom without being noticeably wobbly. Or make the wheels out of sculpted prims so the visible part of the prim extends past the physical bounding box.

I release these ideas to the public domain.

Thx guys.
Guess I'll live with it for now - maybe make a selling point of the car suspension makes you feel like you're riding on air...........