Patrice,
Just for your reference, here's the original lunar rover model rendered in its native environment with 3DS Max' physically based raytracer. The high-quality production render took nearly 45 minutes to complete by the 4 worker threads on a genuine 3GHz quadcore i5 CPU with 8GB of RAM.
As you can see, the wheel guard shields should be substantially more maroonish, rather than yellowish like in your ObjReader renders (see also the genuine lunar vehicle wheel pictures you uploaded earlier).
Just let me know if you'd like to have more finely detailed renders as well.