Cars come with a lot of adjustability. You can use that adjustability to make a vehicle better or make it worse. With so many options to change like ride height, strut settings, alignment, and tire pressures it can be overwhelming when trying to make a car perform better. There are tools available that can help take some of the mystery away when it comes to car setup. One of those tools, and in my opinion the most important one, is a tire pyrometer.
A tire pyrometer is simply a tool that measures the temperature of a tire. There are laser pyrometers that measure heat at the outside of the tire, and there are probe style pyrometers that you poke into the tire’s rubber to measure the temperature inside the tires. The probe style pyrometers are more effective at measuring data near the cords of the tire which will tell you more about what the tire is doing. High-end professional racing teams use the probe style pyrometers for more accuracy.
What does the temperature of a tire tell you? Great question. Tire pyrometers are used to measure temperature in a tire across the tire’s surface area and the difference in those temperatures can indicate information about your setup. Generally, three temperatures are taken along the tire at the following locations:
Tire Temperature Locations
1. Outer edge (approximately 1 to 1.5 inches from the outside edge of the tire)
2. Center (at the lateral center of the tire)
3. Inner edge (approximately 1 to 1.5 inches from the inside edge of the tire)
The difference in the temperature readings across the tire can indicate if a tire is over-inflated or under-inflated. Additionally, differences in the temperature can also indicate if a tire doesn’t have enough negative camber dialed into the alignment.
The process to determine what the correct pressure is for a tire using a pyrometer is as follows: First, you will need to run the car under hard acceleration and braking to bring up tire temperatures. Second, you will need to immediately measure three tire temperatures (laterally across the tire) for each tire. Then you will look at the data and determine if the tire needs more or less tire pressure.
We spoke to Marc Sanzenbacher, senior manager of Motorsports at Toyo Tire Corporation, to discuss the correct pressures for Toyo’s Proxes RR racing tire. According to Marc, the RRs like to be between 32 and 36 pounds during operating temperature (racing temperature). He said the optimal operating temperature for the Toyo Proxes RR is between 160 and 220 degrees Fahrenheit. The variance between 32 and 36 pounds of pressure is dependent on wheel width, vehicle weight, and driving style. The data from a pyrometer will help dial in the exact pressure that will make the car more drivable and (everybody’s ultimate goal) bring down lap times.
Heat dissipates and tires cool quickly. To get a valuable data set, it is crucial to check tire temperatures and pressures immediately when the car comes off of the track. Having a crew member at the pit wall right after a hot lap pays huge dividends when it comes to grabbing tire temps. If you take the time to drive your car off the racetrack, slowly all the way through the paddock, get out of your car, take off your helmet, and then use a pyrometer to check temps, chances are you will be getting bad data due to the tires cooling.
Not only is it better to get your temps immediately when the tires are at peak racing temperature, but having a good tool to help you quickly grab all the temps and organize the data will make your life (and the life of your crew members) immensely easier. Intercomp Racing makes a probe style tire pyrometer available direct or through Summit Racing that stores three temperatures for each of the car’s four tires. This makes it easy for a crew member to quickly run around the car and grab the twelve different data points.
Once tire pressures are set to the optimal numbers using the data from the tire pyrometer, then it is time to use the pyrometer to determine if a vehicle’s camber settings are accurate. This is done by taking the car back on track and running it really hard through a number of corners. You do not want to complete a cooldown lap, you want the tire temperatures to be representative of what the tire is handling as it is working through a corner. Is the outside edge of the tire doing too much of the work? The tire temperatures will let you know.
The best-case scenario is as a vehicle is traversing a curve and begins to lean on the suspension, the outer wheel is stood up vertical so the entire tire surface is working to hold onto the asphalt. If a tire starts out straight up and down, once the suspension compresses in the corner, the top of the tire will lean outward, which means the inside-bottom of the tire will not exert as much downward force as the outside. Thus, the outside of the tire will be hotter than the inside due to more friction with the surface of the track.
To compensate for the lean of the vehicle, negative camber is put into the alignment, which means the top of the tire is leaned in toward the car while the vehicle is static. When the vehicle is in a curve loading the suspension, then that wheel is now straight up and down, allowing for the entire surface area of the tire to do its job. The temperatures from the tire pyrometer help determine if more or less negative camber is required by the heat difference between the outside and inside edges. A hotter outside edge needs more negative camber, a hotter inside edge means more positive camber.
Craig Watkins, a retired engineer for Flying Lizard Motorsports, discussed the importance a tire pyrometer makes when it comes to setting camber, “Everything a race car does, it does through its tires. Tires are the most important thing on a car, so it is absolutely crucial the tires are aligned correctly to do their best work.” According to Craig, he will make as small as a 0.2-degree change to a car if the data from the tire pyrometer indicates a change is needed.
To know how much of a change to make requires more tools. In this case, we use Smart Racing Product’s Smart Camber gauge. If the outside of the tire is warmer than the center and inside of the tire, we will add more negative camber and then test the car again. The process for adjusting camber (and how that change will affect toe settings) was covered in an earlier article here at TURNolgy: Easy Accurate Inexpensive Do It Yourself Alignment.
A tip from the pros when using a tire pyrometer effectively is to always insert the probe at the same depth. You want consistency when taking these temperatures. Differences in temperature readings should be because the tire is at a different temperature, not because you didn’t push the probe in far enough at one location and pushed it in too far at another location.
One thing to be careful of is to press the probe in and pull it directly out without moving it inside the tire, these tools are small accurate measuring devices and you can easily snap a probe off in a tire. I’ve done it and it sucks. While doing research on this story, Chris Berg from Intercomp told us the probes are designed to be inserted at a 45-degree angle to keep it from getting stuck in the tire — who knew? Whichever angle you choose, just be careful. Most pyrometers allow you to buy replacement probes separately, but nobody wants to spend money on tools they didn’t need to break.
Bring it in hot. Pro teams bring their cars in off the track with the tires at peak racing temperatures in order to glean accurate data. Have good tools with fresh batteries to ensure you get good data after a session on track (these sessions aren’t cheap). A pyrometer which stores multiple tire data is really helpful in collecting data quickly. Quickly is the key, as the tires start cooling the moment the car stops moving. Being organized with pre-printed notes is also helpful for using the data later to make decisions in the garage about what to do to make the car faster.
One more tip about the tip: Hold the tip of the probe in a warm tire for a moment before you take a reading to heat the probe up, so your first temperature reading on the race tire is accurate.
Besides tire pyrometers that have memory storage, like Intercomp’s, there are tire pyrometers that are a combination pyrometer and tire gauge. Some of these gadgets not only store multiple tire temperatures per tire, but they will also store tire pressures too. Some will allow you to take cold pressures (before a lapping session) and then hot pressures (after a lapping session) and store both of those data points in the memory.
One of the tricks to using these gauges is the order of operations. You have to hit certain tires in a certain order and collect tire temperatures in a certain order (outside-in) or it will screw up the data sets. These tools are efficient, but sometimes just a pen and paper works well too.
What It Can Do For You
Racers are always searching for that edge. Car setup can make the difference between finishing on the podium or ending up in a gravel trap. Using data from a tire pyrometer will assist you in making smart decisions about your tire pressure and vehicle alignment. Data from a pyrometer can also tell you other things about your car you may not know is happening.
In a rear-wheel-drive car is your right-rear tire hotter than your left-rear tire? That means you have a limited-slip differential that isn’t working like it should anymore, and you are losing time on the track by spinning that right-rear wheel. Without looking at tire temperatures, you may have never realized it was occurring.
It doesn’t matter if you are an autocrosser, drag racer, time trial competitor, road racer, or circle track driver, regardless of your motorsport choice, you use tires. Tires are the only thing between your car and the racing surface. A tire pyrometer is the best thing you can add to your toolbox to ensure your tires are working at their optimal ability to get you down the track and to the finish line first. Long story short: get one.