Problems with collision checking

[joevenzon]

OK. As of R2396, collision boxes are now automatically generated based on the bounding box of the body model combined with the bounding boxes of the wheels, with the lowest position equal to the lowest body model position minus 20% of the body model height (to avoid scraping the bottom of the car on the road too easily).

I tested it with the open-wheeled cars and they seem to all work perfectly as I'd expect, except the T73... can't figure out why.