Speedway Tech Talk - Wheel & Tire Selection Basics
Speedway Motors employee Steve talks about a few options available at Speedway Motors to help take some of the mystery out of finding the right wheel and tire combination to fit your project.
The first tool Steve talks about is the Percy’s Wheelrite. This is a fully adjustable tool that fits over the lug-nuts of your vehicle. Then you can rotate your hubs and set your tire section width, and wheel diameter. It has a hoop across the top to show for any fitment and clearance issues, which can come in handy on the front axle as you can now check for contact points on your fenders without having to actually have a wheel and tire on the vehicle.
The next piece of equipment Steve talks about is the Speedway Motors Bolt Circle Template. The template is preset with multiple bolt patterns. It is simply a matter of matching up the pattern to the lug nuts or bolt-holes and you have the pattern of the wheels. That cuts out trying to measure the wheels or hubs.
Steve also shows us how to find the backspace of wheels. This is accomplished by laying a straight edge across the back of the wheel and then measuring down to the back face of the wheels. The wheel Steve uses in the video shows a total of 4 inches of backspace.
Steve also discusses the overall caliper measurement, and how to arrive at it. Essentially, the internal diameter minus 1/2-3/4 of an inch is needed for the caliper rotation. The E/T wheel that Steve has on the bench measures 14 inches internally, so that would leave a minimum of 13-1/2 inches of rotating area needed for safe operation.
He also takes some time to discuss section widths of tires. Steve says that it is not uncommon to have two tires of the same size from different manufacturers that actually have different section widths. The section width of a tire is the outside to outside measurement. The two tires that Steve has for us on the bench today are both 8.20-15 in size. One measures a section width of 9-1/2 inches, and the other one measures 8-3/4 inches. Where this matters is tucking these wheels up under a fender, or if your project may have some excessive body roll or softer sidewall in the tires, the width could result in rubbing and contact. Steve recommends 1/2 to one inch of clearance between the sidewall and the metal of your car.