I plan on getting some new wheels soon and need to know the stock offset for a oo t/a convert.
the wheel i want are the new c6 black 5 stars there are 18-8.5 and i think the offset is 56mm. i just wondering if they will fit?

 

The stock wheels are 16x8" with 55mm offset. For an 8.5" wide wheel, and a 56mm offset, you will be adding about 0.3" to the backspace and about 0.20" to the frontspace. Wheel and tire will fit fine, no problems.

You might want to consider a wider wheel.... say at least the 18x9.5". You can fit wider tires, and it just looks a lot more aggressive. You could use an offset anywhere from 45mm (edge of tire near outer edge of fender) to 56mm (edge of tire about 3/4" in from the edge of fender).