It's z-fighting, and the reason it's more prominent with some tracks than others has to do with the precision of the depth buffer. On large tracks, the depth buffer will often be less precise because it has to be larger than on smaller tracks. For objects that are really close, a small change in the depth buffer precision like this can trigger z-fighting on some tracks, while others are just fine. Not really a track problem, and not really a car problem - just a synergy of bad luck. (Someone smarter than me explained it to me some time back.)
There are settings in CM that can aid in this, but I can't come up with any specific advise right now.
For reference, I have no similar problems with the same car on the same track, and I'm just running default settings for everything that should matter. And the Dallas/Cadillac is a really nice car.