In order to get the maximum performance from your tires, regardless of whether you’re auto crossing, doing an open track or racing, you need to have the correct tire pressure and the optimum chassis setup. The best way to determine both of these is through the use of a probe type tire pyrometer.
These are from Longacre Racing and the one on the left is a single reading type. If you use this type, you should have two people taking temps so that one person can be writing down the readings while the other is taking them. It is important to take the temps as quickly as possible. The one on the right will read and record all 12 temps and store 10 different sets of temps. It also has a built in stop watch. This tool can determine the temperature of the surface of a tire using a metal probe that’s inserted into the tread surface. We do not recommend the use of infrared pyrometers because the results can be inconsistent.
You need to run about a half a dozen hot laps around the race track or a skid pad to get the tires up to temperature. When you come into the hot pit, have someone there to check your tire temperatures as soon as possible. That’s because the temperatures will equalize quickly.
You want to take three temperature readings across the surface of the tire: the inside edge of the tire, the middle of the tire and the outside edge. You need to record these readings so you can refer to them later. Always check all four tires and always check them in the same sequence. If you start with the right front tire and go around the car in a clockwise direction and finish with the left front tire and do it the same way each time. When taking the tire temperatures, make sure that you insert the probe the same depth each time. Usually, an sixteenth to an eighth of an inch is fine.
It’s important to write the temperatures down so you can compare them later on. If you see a tire that has a temperature that is warmer in the middle than on either edge, it usually means your tire pressure is too high. If the middle temperature reading is lower than either of the inside and outside edges, that usually means the tire pressure is too low. If the outside edge of the tire is hotter than the inside temperature, that means you need to change the alignment of the tire by adjusting more negative camber in that tire. If the inside temperature reading is higher than the outside temperature, the tire has too much negative camber, and you need to reduce it.
Generally, if you have a variance in temperature of more than 10 degrees, you will want to make the appropriate adjustments to attempt to equalize those temperatures. When making adjustments, make them in the same relationship to the temperature difference. Make a large adjustment if there is a large temperature differential. Let’s say that the center temp reading is over 30 degrees cooler than the edges then add at least 5psi of air. Add only 2psi if the temperature difference is 10 degrees. The same applies to camber adjustments. Depending on the type of tire and the track, many times the car will be faster with the camber set so the inside of the tire is hotter. You can only determine this by a back-to-back test.
To get a starting point for your tire pressures and chassis setup, talk to your tire supplier and they can usually give you a good starting point. Many times, the tire manufacturers will have their engineers at the track and they will be an excellent source of information on tire pressures and chassis setup. This whole process can be somewhat time-consuming but it will pay big dividends in faster lap times.
This is a link to a video we shot on using a tire pyrometer. https://youtu.be/GnpUtH3RSuE