I am staying with stock 17's and need tires looking at Hankook Ventus R-S3 in 255/40/17 for rear and 245/40/17 or 235/45/17 front, what front size will be the better match for rear tires? I am on stock suspension, 05 M6 car. How do can I find tire diameter for each tire size? Anyone running a staggered fit on stock 17's, what sizes work? Thanks for your thoughts.