Well, you don't necessarily need to have motion blur done to have the wheels blurred. Sure the wheels wouldn't be (very) blurry if you would use fast shutter speed setting when taking a photo in real life, but since the water spray is so misty and the picture is that dark I think slow shutter speed would have been used and therefore the wheels should be blurry.
If a car is in motion you won't be able to get that sharp picture of the wheels, they should be atleast a littlebit blurry.
That looks fantastic dude! The reflection looks real, really un-detailed! That fuzzy blur around the lights looks tops!
The only constructive criticism i could give you is the rain itself could improve on realism. Inbetween the two front cars, in pretty much the middle of the picture, the rain should possibly be 'thicker' and be making an impact on the ground, that way you can get a perspective on the rain. So just a bit more detail on the closer rain and it would be perfecto! The rain above the cars which is in the background looks great!
just.. deny it, dont post any of "your friend's work," on account of having affiliation with someone that is banned, in RSC (yes.. rsc but still should be considered) don got into a fair amount of trouble i remember a long time back for posting some work done by kidcodea (who was banned for reasons i dont know of.. and wouldn't say anyway), just.. next time, just dont post "your friend's work"
car isnt too white, ur too dark :P
You need more contrast on the car, means a bit brighter light, and darker shadow. More contrast should do the job already, but you should only select the car body, no lights etc.