I'm not a fan of the current matte material, it really lacks of depth, hence why I tried something different. Not so long ago I made a test in the Editor, and with the new upcoming shaders I can make the steel body look like this which I think it's really nice, but the new shaders are not in the game yet so we have to wait for this result.
Pitch-modulated collision sounds (scraping, tire skids etc.) depending by the speed of the collision. For example, tire skids at high speeds to have an high pitch compared to skids at slow speeds.