1. How do you correct the Speedometer after installing 19.5" wheels?

2. What will the effect be on power and gearing be?

1. How do you correct the Speedometer after installing 19.5" wheels?

If the tire you select has a larger diameter than stock, then the speedometer can be corrected in one of several ways. The first involves installing a new speedometer gear on trucks so equipped (e.g. 97-back Dodges). This is an inexpensive ($15-30) method and takes about 15 minutes. GM trucks, '01 and up Fords (also reprogrammable by the dealer) and 98-up Dodges can use an Electronic frequency controller that corrects the signal generated by the vehicle speed sensor. We have them for trucks equipped with 2 or 4 wheel Anti-Lock Brakes (ABS) and will correct the speedometer, odometer, and ABS functions. They are simple to install and come with complete instructions. Installation generally involves splicing into one wire and supplying 12V switched ignition power and a ground. Pre-'98 Fords can be reprogrammed by the owner. We include instructions for owner/dealer re-programming for Fords with your package.

The 225/70R19.5 size will have the least effect on gearing. That size is the same diameter as a 235/85R16 or 265/75R16 and will have no effect on gearing when replacing those size tires. It will have approximately a 5% effect on a truck with 215/85R16 or 245/75R16 factory tires. The 8R19.5 or 245/70R19.5 will give about a 5% reduction on a 235/85R16 or 265/75R16 equipped truck or a 10% reduction on a 215/85R16 or 245/75R16 equipped truck. You will generally not notice much if any of a difference in power going to a 19.5" tire and even less on a truck that has had the power of the engine "enhanced".