[skatepozer23]

different tire sizes will not effect the speedometer reading because the vehicle speed is picked up via a wheel speed sensor.

Actually different tire sizes will mess up your speedometer.

The amount that the speedo will be off depends on how big of a tire you get.

For example if stock tires are 23 inches tall and you upgrade to a 24 inch tall tire then the speedo will be off by by 9 percent