Im gettingthe G-Force KDW T/A's for my stang.

I have the Roush 18" wheels.

They said with these they use the 275/40 18 size on them...

Does this sound good or no?

Would it be good for street driving and not weigh me down or slow me down if I race someone?

 

very nice! Fits perrfectly!

 

What is the width of the rim? 285/40/18 would be closer to stock in diameter.

 

if you are lowered 275/35 would look a lil better IMO. In race tires it's a much more common size than 275/40. I'm going to go out on a limb and assume the street tire market is similar.