This is a little trick I use to make my models look as if they have brake rotors. I know you probally just paint the back of the inner wheel silver and go with that, that’s what I used to do but let me show you how easy this technique is anyway. First take the inner wheel and bare metal foil (chrome) and cut a square a little larger than the wheel. Then apply the foil square and burnish to a smooth finish. Now take the rim and drill out the center cap (only the rear rims) and this will represent the hubs. When you use this tip for the wheels you will be surprised how the wheel draws attention, especially when light hits the foil. You can view most of my models and see this effect on them.