Decent motion blur in mental ray??

[Braiz]

Hi guys... (wasn't sure if the 3ds max forum was the right place to post, so I dropped it here as well)

I am trying to implement motion blur on the wheels of my bugatti, on a pre-blurred backplate. As of now I've only tried true
3d-motionblur, but it's destroying my rendertimes.

Is there perhaps a "secret" way of applying decent, smooth, grain free motion blur in Mental ray that does not imply that time stops, and the world stops spinning?

Thanks in advance