Originally Posted by shabarivas

Here is how tire math works:

Sports pkg tires wheels:

Front: 19 x 9 @ 245/40/19 which means the sidewall height is going to be 40% of 245

so if you wanted to run a wider tire on the same rim... just make sure this formula applies: 0.40 * 245 = 0.35 (or even lower if you can find tires) * X where X is your new width...

similarly in the rear you would run the following:
0.35 * 275 = 0.30 * X (new width)...

You do this to ensure your rotational radius is kept as close to stock as possible (you will otherwise throw off electronics that use revolutions per min / sec off your tire...) - not to mention your speed readout lol..