Join Date: Feb 2009
Location: Sweet Home Alabama
changing to 255/40/18 will fit, but the tires will be smaller in diameter making the speedo show faster than actually traveling. The difference will be about 2.5% meaning when your speedo shows 70, you will actually be going about 68. It is not a big change and the increased width is about 3/8 inch. Half of that will be inside the wheel well. I think 255s look better than 245s on stock rims, but I would go 255/45/18 if I were you. The difference there would be 1% the other way. 70 on the speedo would be almost 71 real speed.
09 GT, Stryker Blue, Sport/Prem
07 Solstice GXP, Mean Yellow, tuned
03 Excursion, 6" Fab lift, V10, 37s
94 Bronco, 5.8L, 35s and rust