lowpoly models look good too if you use nice textures. if you want to create models like doom 3, you need a bit more polys (A BIT) and use shaders like normalmapping and all this stuff.
You first create a high poly model (like your wheel). then you create a normalmap (its a texture with some weird colors, just google for it) and apply it with a shader to a low poly wheel (like 200 polys). then it almost looks like the high poly one. im no friend of normalmapping though :x