With stock tires you get a true reading on your speedo and true MPG calculations. So, if you get larger than stock tires your speedo reading will actually be less and your mileage less? right? So if you are running 31's for example and a 50mph reading is actually 55mph, your mileage calculation will be lower than it actually is; about 10%, right? I was just curious, it doesn't really matter, it's all good fun anyway!