Understanding Tire Temperature

Tire temperature is a very important and advanced topic. The earlier you understand it, even as a beginner, the better you're going to understand the development of your own driving technique. As you get more advanced, this knowledge becomes increasingly useful for maintaining a nice balance over long stints—whether one hour, two hours, or even ten hours in endurance races. It's also critical for managing tire temperature through a single corner.

We're going to focus on tire surface temperature and zoom in to analyze how it affects driving at three different timescales:

• Short term: What happens in the same corner

• Mid-term: What happens in the same sector, such as through multiple esses at Suzuka, or through double-left or double-right corners that are very close to each other

• Long term: How to control temperature and manage tires over an entire stint in the most efficient way possible

Short-Term Temperature Effects: Within a Single Corner

Let's examine what happens in a single corner. When you start braking on a straight line, you immediately start adding temperature to the surface of the tire. Depending on the tire compound and tire physics, that surface temperature might increase grip or decrease grip. In iRacing and with most tires, you're going to have less grip when you start heating up the surface.

Here's the sequence as you approach and navigate a corner:

• You start braking on a straight line and begin generating temperature on the surface of the tire, which actually decreases grip

• The more temperature you get in, the less grip you're going to have

• You start turning, which generates even more temperature and even less grip

• This continues through the apex—you're still using all the grip, still on the limit, still overheating the tires

• Finally on corner exit, you stop being on the limit and the surface of the tires starts cooling down

• On the straight, the hot surface is in contact with the colder track, and temperature transfers toward the inside of the tire and toward the track

• Air cooling also helps reduce surface temperature on straights

The Snowball Effect of Overheating

Understanding this temperature cycle is important because of what happens when you lock up the tires during braking. If you lock up, you gain a lot of temperature because you are overheating the tire. Because of that extra temperature, you now have less grip. With less grip, you abuse the tires because you are now a little bit too fast and the car is not capable, so you start scrubbing more. This creates a snowball effect where it gets worse and worse: more temperature leads to less grip, which leads to more scrubbing, which leads to more temperature, which leads to less grip, until you really overheat the tires. By the time you get to the apex, the car is really sliding all over the place. Finally on the exit, the temperature starts going down again.

This is very important to know: if you lock up the tire on entry, even if you're not turning, once you unlock the tire it will still have less grip. If you overheat the tire at any stage of the corner, there's no going back—the car is going to have less grip overall. A tiny lock on entry generates less cornering grip throughout the entire corner. Something that happens on a straight line affects what happens during the corner.

Brake Bias and Temperature Balance

The locking example applies even when you're not over the limit. Let's say you have a braking bias that is abusing the front tires—you are heating up the front more. By the time you get to turn-in, the fronts are hotter than the rears. There's less grip at the front, and the car is going to understeer. Because it understeers, you turn more, which creates a snowball effect that gets worse and worse. You're understeering all the way to the exit.

In this case, the solution would be to change the brake bias a little bit so the temperature becomes more balanced—a little bit less temperature on the front tires and a little bit more temperature on the rear tires. When the temperature remains more stable between front and rear, the car handles more predictably. However, if you get too much oversteer, the rears become too hot, and there's a bigger tendency for another oversteer situation to happen because now the rear tires are hotter.

Remember this fundamental principle: what happens at corner entry will affect the rest of the corner until you exit and cool down the tires. Eventually the temperatures will return to a very close balance. Whatever you do on entry will affect the rest of the corner.

ABS and Braking Pressure

This is why it's so important to not brake too hard on entry, getting into too much ABS in a car that has ABS, or to do microlocking or locking in a car that does not have ABS. When you brake and get into ABS and keep it at 100 percent, the temperature goes up more quickly than you need it to in order to stop as efficiently as possible. By the time you start turning into the corner, there is less grip.

If you brake just a little bit less—right on the edge—the car is going to stop in a similar manner, maybe a tiny bit less, but because the temperature is going to be lower by the time you turn into the corner, there is literally more cornering grip. That is super important: don't abuse the tires during braking so that you conserve the surface temperature of the tires and use them very well during the corner.

This is why we're discussing this in the braking module. If you abuse the braking and overheat the tires, you're always going to be slower. You won't understand why your rivals are able to carry so much speed mid-corner—it's because they are taking care of the temperature of the tires on entry. They're not abusing the braking. We're talking about very small differences here: maybe just avoiding ABS activation, or maybe just not microlocking that much.

Even turning in too much on entry already starts overheating the front tires, and then mid-corner there's even less grip available.

Mid-Term Temperature Effects: Sequential Corners

When you overheat the tire in one corner, there are short-term effects, but you also have mid-term effects. Mid-term effects occur when you have another corner that is very close to the previous corner.

Here's what happens: if you abuse the brakes and lock up before the first corner, you overheat the tires through that entire corner. On exit, the tires cool down a tiny bit, but then there's another corner already. You already have to turn in, and that second corner will suffer the consequences of the lock-up from the first corner. It's that important.

The higher the temperature, the less grip you have. This is a temperature-to-grip relationship. What you want to do is take care of the temperatures through the first corner, exit it, let the temperature go down a little bit (though it won't go down too much because you already have another corner), and then enter the second corner. In an example where you locked up in the first corner, you had less grip throughout the entirety of this compound corner or full sector. We might be talking about two-tenths, three-tenths, four-tenths, or even five-tenths that you're losing because of a micro lock-up that overheated the tires.

Practical Example: Front Lock-Up Effects

Here's a practical example of how locking up the fronts a tiny bit makes you understeer for the rest of the corner because of how you overheated the fronts. When attempting to lock up a tiny bit intentionally, even after releasing the brakes and restarting the braking process, trying to get as much rotation as possible with proper downshifts and the right speed, the car just understeers. There's absolutely no rotation—it just does not want to turn at all, just because of a micro lock-up that happened a few seconds before.

A little bit of lock-up, even after resetting and trying to make the corner normally, won't work. It's not going to happen just because the fronts were locked up three seconds before. This is an extreme example, but it demonstrates exactly how it works on a subtle level. If you do a micro lock on the fronts—even if it's not fully locking, just micro-locking a little bit—it's already going to make the car understeer more by the time you start turning in, just because you overheated the surface of the tires.

In a more aggressive lock-up example, after locking up more than intended and trying to reset and brake again, you actually overheat the fronts so much that they start locking up even more easily. Trying your best to turn into the corner, you're just locking repeatedly because the inside front tire (the right front in this example) is completely overheated. Not the other tires—just this one. Because this tire is necessary to turn into the corner, you can see that you're locking the right front while the left front is fine, leaving a trail of only the left front.

The surface temperature on that one tire alone is enough to completely kill the performance of that corner just because of locking up a little bit. This demonstrates that it always works the same way: micro lock-up, back on power, then at the right speed, downshifting as much as possible, trying to make the car turn—it does not turn at all. It's always going to be understeering after a front lock-up like that.

Rear Tire Lock-Up Effects

The opposite situation involves locking the rear tires. Bringing the brake bias all the way down (like five or six percent) can cause the rear tires to lock. Even a little bit of locking the rear—not even a full lock—creates problems. You can tell when you're locking the rears in a rear-wheel-drive car because the engine sound goes down very aggressively. That's because you're locking the end that is driven by the engine. If the rear tires lock up, the engine also turns off and you can hear it. When you unlock, the RPM goes up again because now the rear tires are back and running.

After locking up the rears for just a fraction of a second and trying to do the corner normally, the result is different. The brake bias is different, which affects it, but the bigger factor is the fact that the rear tires were locked. Locking up the rear tires overheats them, so they have a lot less grip when you turn in. The same effects that apply when overheating the front tires and continuously understeering throughout the corner also apply for mid-term temperature effects and also apply to the very next corner if the corner is close enough.

Understeer from Overheated Fronts

In an example where you start understeering a little bit on purpose by turning a lot, you can actually see the understeer as you paint the track. After that, you get back on power and there's another corner about four seconds later. When you try to do this second corner—even trying to trail brake a little bit more to make the car turn—because you did understeer and overheat the fronts on the corner before, this corner is also going to understeer heavily. Whatever you try, the car is not going to oversteer unless you really abuse something or try something to compensate for the temperature imbalance that already exists.

Oversteer from Overheated Rears

The same thing happens in the opposite way. When deliberately overheating the rear tires by trying to get a little bit of entry oversteer—a micro one, not a big one, but enough to overheat the rear tires more than the front—then getting back on power a little bit aggressively, you can see the car painting the track. Now the car has more temperature on the surface of the rear tires than the front. When you start turning in on the next corner, immediately you can see the car already losing the rear easily.

In the cockpit view, this becomes even clearer: a tiny bit of oversteer on entry (you can hear the sound), getting back on power with more corrections using the rears more than the fronts, and then with one downshift on the next corner, you can already see how the car is really wanting to oversteer. It requires corrections, even coasting for a while, and then finally when you get back on power just a tiny bit to show how the rears are dead, you can see that the car just goes.

That's how easily you can affect the balance of the car depending on whether you abuse the front tires or abuse the rear tires in the moments before.

Long-Term Temperature Effects: Over a Stint

Long-term effects are what happen over a whole stint. You start the stint, you're doing lots of laps, and you're overheating, overheating, overheating until you get to a point where you are just maintaining that temperature. Doing lap after lap after lap, the temperatures are stable. This is how it looks long-term.

However, if you were to overlay the short-term temperatures, it would actually show a repeating pattern: corner after corner after corner, every corner you do, you overheat and then it cools down on the straight. If you had a long straight, the pattern shows this clearly. If you had four corners followed by a straight, it would always show one corner, two corners, three corners, four corners, then cool down a bit, then repeat. As you still heat up the carcass over time, the temperature will never go down that much if you're really on the limit over a full stint.

Basically, what you do in the short-term effects affects the mid-term effects and affects the long-term effects in a snowball effect.

Real-World Coaching Example

Here's a coaching example with a very fast driver, Alberto Nasca, a professional driver and YouTuber. During an iRacing session, he was abusing the front tires because he was braking too hard. He was always overheating the fronts and getting a little bit more tire wear. After three laps in his first session, he had 91 percent left on the front left, 92 percent left on the front right, and then 94 percent and 94 percent on the rears. This was before investigating what he was doing.

After realizing he was understeering too much, we discussed that maybe we didn't need to change the setup—we could only change the way he was driving to manage the temperatures a little bit better and get the car to rotate more so he would abuse the fronts less. In the first attempt of trying what we worked on in the session (a one-hour session), the tire wear actually became 93 percent, 94 percent, and 93 percent on the fronts, with still 94 percent on one rear. He was actually going faster, abusing the front tires less, and not using the rears more—well, a little bit more, but in a much more balanced way where he was actually using up all four tires in a much more consistent and balanced way.

This was over just three laps. Imagine if you're doing a one-and-a-half-hour stint, double-stinting a tire on an endurance race. This two percent change in two or three laps could mean 10, 15, or even 20 percent difference in tire wear because you adjusted your driving a tiny bit. But that tiny bit in one corner snowballs into a totally different behavior during the entire stint, and that can mean seconds per lap at the very end of the stint if you take care of the tires.

Managing Temperature Through Braking and Downshifting

If you understand how to manage the temperatures and how we can affect our braking pressures, our brake bias, and our engine braking while thinking about tire surface temperature, you can make significant improvements.

Two Braking Approaches

Consider two situations: In situation A, we're braking very hard with heartbreaking pressure, then a little bit of threshold braking, then trail braking into the corner. We're downshifting a little bit late—doing three downshifts sequentially—and then turning into the corner. In this situation, the car is understeering.

What we can do to control in a very subtle way the tire surface temperature balance between the front tires and the rear tires is to maybe brake a little bit less. In situation B, we're going to brake a tiny bit less—like five percent less or something—and stay a little bit under threshold, then try to brake normally, kind of keeping the same pressure as while trail braking. But now instead of downshifting late, we're going to downshift earlier.

To summarize:

• Situation A: Braking pretty hard and downshifting late

• Situation B: Braking less and downshifting earlier

In situation B, because we're downshifting earlier, we are adding more dynamic brake bias to the rear tires because the engine braking is higher. That is heating up the rear tires more. But we are braking a little bit less, so we are also heating up the fronts with less difference. In situation B, when we start turning into the corner, we have more front grip and the car literally rotates more just because we brake a tiny bit less and downshifted a little bit earlier.

These tiny adjustments can make the car go from total understeer to even spinning without changing anything in the setup and without even changing the brake bias. Just the pressure of braking and the timing of the downshifts can make a car get to a corner with the front overheated or the rear overheated.

Applications in Endurance Racing

This is incredibly useful if you're driving with someone else in an endurance race. Let's say Driver A heats up the front tires a lot more, while Driver B heats up the rear tires, and you never get to a setup agreement because one driver is always destroying the fronts and the other is always destroying the rears. Each thinks their setup approach is better, creating conflict.

It's super useful to understand how you can adjust your driving to adjust the tire wear and the tire temperature so that your driving adapts to different setups. Of course, at this point you should discuss it and try to check telemetry to understand what's happening. Someone might be braking a little bit too hard and downshifting too late, while the other might be braking a little bit too soft and downshifting too early. You have to see exactly what combinations generate the temperature more toward the front or the rear so you can solve the problem and have a setup that satisfies everyone.

Tire Compound Variations

Here's an important consideration about tire surface temperature: most tires will have less grip with more temperature on the surface. Some tires will behave in a very consistent way where you don't feel too much difference, and other tires might even gain cornering grip when you get temperature on the surface. This is very rare, but it happens.

There's a famous example from real life: Fernando Alonso in 2008 was turning a lot on turn-in and really overheating the front tires because that would actually give more grip to the car mid-corner. Basically, he would turn in on entry, overheat the tires a lot on turn-in, and then as he got into the corner deeper, the tires would gain grip and the car would point more because of that generated surface temperature that he was doing on purpose. Of course, this is a very rare example. In iRacing and with most compounds in real life, you're going to have less grip with more surface temperature.

Practical Demonstration: ABS and Balance

Here's one obvious, clear example of how adjusting the relationship between how early you downshift versus how hard you brake affects the balance of the car. This car has ABS, so if you brake too hard, you're just going to get that ABS more aggressively, generally more on the front tires first, and that's going to affect the way the car is going to behave heavily because of the tire surface temperature.

Example 1: Light Braking, Aggressive Downshifting

In the first example, there's not a lot of braking but very aggressive downshifting. This means more rear temperature and less front temperature, so the car is expected to have more rotation. For reference, by the time the car crosses a particular shadow on track, it's at approximately 128 kilometers per hour. The result: rear end loses grip.

Example 2: Heavy Braking, Late Downshifting

In the next example, braking more to get more ABS on the front tires, creating more temperature on the front tires. (If you change the brake bias, that's also going to affect this, so make sure you're thinking about all these small factors.) Not only braking more, but also downshifting later. Checking the speed reveals actually carrying more speed this time. Yet the result is heavy understeer—heavy, heavy, heavy understeer—just because of adjusting these small factors and adjusting the way temperature was being generated on entry. That temperature will decrease the grip on the end that has more heat, and that will completely affect the balance of the car into the corner.

These examples are shown aggressively so you can feel the extremes. The more you get used to these extremes, the more you can recognize and work with the subtle differences in your normal driving.