well..and how about not doing the tyres really black .. in the real, they are not black at all

so I would recommend to make it more bright, and then maybe add a little bit fall-off in the diffusion map slot
a lot of work can be as well achieved with bump maps and specular maps
but I think your problem is that you have it too much black.
here is the wheel I did for my Cadillac CTS-V
I also think, that if you`re not doing a big render of the wheel alone.. you don`t have to pay that much attention on the wheel