Are you setting up a rear-end gear change, tire sizes, maybe a new stack of gear ratios? If you are you know that crunching the numbers by hand can be a tedious task. Figuring out the final drive ratio, and rev-limiter settings for your performance vehicle are as important as the high-end parts you use. If your setup does not agree with your parts your vehicle’s performance will suffer.
Our friends over at Mark Williams Enterprises eat, sleep, and breath axles, rearends, driveshafts, and brakes so they have devised a little cheat sheet for all you would-be race car tuners. Mark Williams offers three racing calculators to make your math a little simpler, just plug in the numbers you have and get a computer generated response free of grease smeared scratch paper.
The first user interface is their gear Ratio and RPM calculator. With this application you can select a transmission and tailor the gear ratio package to your liking. With this data entered you can then set engine RPM and see to what speed that correlates in each gear. A tool like this will really help you visualize how a custom gear set will behave with you engine’s powerband.
The second calculator is a life saver for anyone who has installed huge, multi-piston calipers only to find they don’t have enough master cylinder volume to support the big brakes. Mark Williams Enterprises takes the guess work out of picking a braking package that will work in your application with their brake master cylinder level/pedal ratio calculator. By applying the pressure you wish to impart on the brake pedal with your foot to result in a specific amount of brake line pressure, the calculator generates the necessary ratio for pedal pivot. Several common master cylinder diameters are supplied but a box for custom sizing allows the user to input their own specifications.
The last of the racing calculators helps with those pesky mixed-units tire sizing codes. As you may be aware, traditional tire sizing is comprised of three numbers, a tread width in millimeters, an aspect ratio that gives you the side wall height, and the wheel diameter. None of these numbers give you the actual diameter of the tire, which of course affects gear ratios. Say you would like to install wider tires for a larger contact patch and better traction, but you don’t want to change the overall diameter. You will need to change the aspect ratio for a smaller sidewall or change to a smaller wheel diameter. This calculator allows you to plug in the numbers you read on the side of the tire and generates a much more user friendly set of data. Using the metric tread width, percent aspect ratio, and standard wheel diameter, you are given the tire overall diameter, width, sidewall height, and rollout (circumference) in inches.
With these calculators, you can better plan your purchases and be sure that the parts combination you select will be a successful package. If you have any further questions about selecting the right parts, or calculating give Mark Williams Enterprises a call.