I know you are going smaller, but as an example, if you went larger, you could blow out your clutch in no time because it is going to take more torque to turn the wheel. I've personally seen it happen. Anyway, with a smaller wheel, your acceleration will be faster, but you will also loose top speed. The other thing....your car is going to show a lot more miles than it really has, because your tire will be going around many more times than is should in a mile. As for the computer, it is calibrated for a certain diameter tire. That means it gives just the right amount of power at the right time, and a million other little things. Its really not worth it, and is going to be hard on your car.
