@B.Y.O.B.: Thanks for the offer to help rendering, I think I will do the new render in 1920*1200. Because with the resolution at 3200*1200 the flm files are 350-400mb which makes sharing them a bit difficult.
I will try adding a texture to the tire for more details but I don't really now where and how I should add imperfections.
@zeealpal: I wanted to make the rim look a bit like a matte bronze but like you said it should be more reflective.
The glass is more a mesh based problem I think. Because it's exported from a computer game the mesh is based on triangles that create weird effects when I add subsurf. I'm pretty sure the glass will look better after changing the triangles to quads.
EDIT: Began to redo the headlights to make them look more realistic. Rendered this picture to 2,26kS/p to test my new Core i5 3450 ^^