First off, and you may already know this, for textures like the hockenheim background, you only want to clamp the texture in the V (vertical) direction, not the U (horizontal) direction, because the texture is supposed to repeat in the U direction. That means you want to set the clamping flag to 3:
http://svn.vdrift.net/viewvc.cgi/trunk/l...or&view=co
However, even setting it to 3, the hockenheim background is still goofed up. My guess is whomever modeled the track used weird texture coordinates for it (relying on the texture repeat) instead of using coordinates in the 0..1 range.