my friend sold me some 18" racing hart c2 and the bolt pattern is the same as the v6 mazda6 but the off set of the RH's are 42mm. i looked up the offset on the mazda 6 and it said 55-60mm. what are some potential problems will i see in the future or will there be any? is this ok to run on my 6? sorry im new!!!!

 

Depending on the width, the 42mm offset may work (but it would be tight on clearance to the wheel lip in the rear.) Best bet is to fit it up to your car and see where it fits....

 

The wheels will stick out farther than the stock ones, and may well cause the tires to rub the fenders. With stock height and stock tire size or close, 45mm is about the minimum you can expect to get away with.
Having the rear fenders rolled should help unless you're running really large tires.

 

My first set of rims were 42mm and I rubbed with my fenders rolled. So I got rid of those and got a new set of rims.