Different tread designs of...
Different tread designs of these dirt tires indicate different manufacturers. In front is the uncut block-style tread in a Goodyear Eagle. The heavily cut block-style Hoosier is stacked behind that. On the top right rear, there is a chain pattern tread. The choices are sometimes confusing for the average racer. The real goal is to get the most tire footprint on the racing surface.
Correctly analyzing your tires can lead to maximum performance. Many factors can and will influence how well the tires work. The proper way to evaluate the tire temperatures and wear, primary indicators of how the tires are working, is what we will cover here.
The first indication of tire performance comes from taking tire temperatures while later indications involve tire wear. Dirt racers will tell you that taking temperatures is not practical. They may be right in most cases. Dirt teams usually need to wait longer, after the tires have worn considerably, to know how everything is working, but they will still have some indication.
It is important to know that the relationship between high and low temperatures is the same as for high and low wear. A high-temperature area of a tire will also be a high-wear area later on. Asphalt racers can utilize both tire wear and temperatures. For dirt racers, the wear information is probably most useful.
The tread designs produced...
The tread designs produced by the Hoosier Racing Tire Company allow the racer plenty of opportunity to measure the tread depth to determine tire wear. We can get indications of proper tire pressures as well as cambers by measuring tread depth at points across the face of the tire.
The reaction to tire temperatures must be immediate if those temperatures indicate that changes are needed. I have seen teams ignore obvious camber or pressure problems and change basic setup parameters to help the car handle better. Evaluating the setup in the car cannot begin until the tires are happy. Only then should we attempt to evaluate how the car is reacting in the turns.
We usually know the approximate starting pressures and cambers for our cars. As the car is run, these are the smallest changes that will be made. The most important reading of the tires will eventually involve tuning the setup. Let's start with the pressures.
Reading Tire Pressures
The optimum tire pressures are dictated by the magnitude of the load on the tire and the forces trying to roll the tire over as the car goes through the turns. We need to start on cold tires with a number that represents the optimum hot tire pressure minus the amount the tire pressure will grow due to the temperature increase from a cold tire (one that has yet to be run at speed) to a hot tire (one that is fresh off the racetrack after a hard run).
Using a high-quality memory-type...
Using a high-quality memory-type tire temperature gauge pays off in the long run. Tire data is the most important indicator of your car's performance. Keeping accurate records helps the crew chief make critical decisions about chassis setup changes.
There is a certain amount of backtracking involved in the process of determining proper tire pressures. For example, suppose there is an 8-pound gain in the right-front (RF) tire pressure after a run, and then a setup change is made to take some of the load off the RF tire, putting it onto the left-front (LF) tire. With that change plus the associated reduction in the amount of work the RF will be doing, the next run may see only a 6-pound gain in pressure. The starting pressure will need to be increased by 2 pounds so that our optimum pressure will be reached.
Wear and Temperature
Tire temperatures will tell how the load on the tire is distributed across the whole contact patch. The greater the pressure, the more work that portion of the tire does, and therefore the greater the temperature. From a quick glance, tire pressures and temperatures, together, can indicate how the tires are working. Immediate changes can be made based on this information.
Tire wear is more subtle. More laps must be run for indications of how the tires are working. Although this is a very good indicator, it does nothing to speed the process of chassis tuning. It can help us to understand if the changes already made are indeed correct.
Let's go through a typical test or practice session and analyze the data and the changes to be made. First run the car for two sessions to make sure the tires are clean, the engine systems are working, and that the track is sufficiently clear of any dirt or debris.