Kart Tire Pressure by Conditions: Hot, Cold, Grippy, Green and Wet

This will be the ultimate guide for setting up tire pressures and having a general understanding of what to do based on all the different conditions. Now the different conditions are going to differ a lot, from the track temperature, whether it's hot to when it's cold, to the grip level of the track, between when there's grip or when the track gets slippery, to also obviously the conditions, whether it's wet, whether it's dry, or whether it's drying up of course, and also it depends a lot on the tire compound, between hard tires and soft tires.

Of course, what I'm going to share with you is just a guide, a rule of thumb of how to set your kart tire pressures based on the changing conditions. But of course, it will vary from time to time. And you should obviously keep this just as a rule of thumb, a guide that has, I think, a lot of value and clears my decisions a lot. And I can say it works like 90% of the time. So I'm very confident on what I'm sharing here.

Should tire pressure go up or down on a cold track?

So let's get started. So the first condition that will change your tire pressures is the track temperature. That's why you always have to measure the track temperature, because it plays a huge factor in your tire pressure decision. If the track temperature is very low, you will obviously have to run high tire pressures, whereas if the track temperature is very high, and it's 65 degrees Celsius, like we've had many days consecutively here in Italy in the last two, two, three months between July and September, so if that's the case, you will have to instead play with very low tire pressures.

But again, at the end of the day, the target tire pressure hot, it's what counts, even though I am a firm believer that it varies between track to track, and it varies in the track temperature conditions. For example, let's say, averagely during the whole year in the different tracks, let's say on average your hot target temperature for an MG tire supposedly is 0.90 bar. So it's 0.90. I don't know exactly how much that is for PSI, you can Google the conversion from PSI to bar, but let's say it's 0.90 bar.

What I've noticed over the years, and that has helped me win a lot of races, is that if the track temperature is very cold, let's say in January, the track temp may be zero degrees, my new target pressure will not be the same as it used to be in the summer at 60 degrees track temperature. So maybe, even though the average of the year is 0.90, in that specific case I'll try to come out at 0.95, and see whether that's quicker than 0.90. And I'll make a change, and I'll try to see, okay, then we're gonna stop, we're gonna drop it to 0.90, and we're gonna see how's the grip changing, how the lap times changing. If it's worse, we try to lower it even more, 0.85. And if it's even worse, okay, then, right, we see the direction is to be a little bit higher, so around 0.85, maybe we increase it even more.

So what I say is that tire pressures are always a moving target. They're not really fixed in stone, and they're not going to be the same for all the tracks, all the conditions. So you always have to kind of experiment. It changes a lot based on the compounds too, I'll talk more about that later.

So yeah, number one is, if the track temp is low, I'll try to go higher hot targets in terms of tire pressures. So whether that means starting at 0.75 or 0.70, it really depends on many, many cases, even from the rim temperature when you actually set the tire pressures.

Set pressures at a consistent rim temperature

By the way, that's really important. It's something you really need to always remember. You need to have a consistent place where you set up the tire pressures, and you need to do that because you want to have consistent rim temperatures. Otherwise, if you cannot have consistent rim temperatures, because maybe inside of the tent the temperature changes a lot during the day, for example, in the morning inside of the tent it's very cold, during the midday it's very hot, especially if you have a heater inside of the tent in January, February. So you really want to be mindful about that, and set up the tire pressures with consistent rim temperatures. That's extremely important.

Otherwise, if you cannot, then you need to have a calculator that basically converts, based on the current rim temperature, what actual pressure you should run. That's extremely key.

Hot track: lower the hot target

But yeah, the rule of thumb in the winter, with really cold track temperatures, aim to come out a little hotter compared to when you come out in the summer. That's really the thing. In the summertime, if it's 65 degrees track temperature Celsius, which is very, very usual in summer, it's crazy, if it's 42, 41 degrees air temperature, due to the recent global warming increases, of course, it's actually becoming the norm to have above 60 degrees track temperatures. And therefore you need to be ready to have a little lower target. Instead of 0.90 degrees Celsius, it may have to come out 0.82, 0.85, 0.87. You should experiment.

Because in a way, the tire pressure is going to affect the tire temperature, even though it's, I mean, there should be a whole chapter on that, a whole new guide on the relationship between tire pressure and tire temperature, because yeah, it's not that correlated. Sometimes actually dropping tire pressure is actually going to flex more the tire, and it's actually going to heat up the tires more. Sometimes with a different compound it's the opposite, with higher pressure you get higher temperatures. So of course it plays differently with different compounds.

But yeah, normally, if the track temperature is really hot, and if the tires are running really hot, and you are having overheating during the last few laps, then, of course, you need to try to run lower pressure, even if that means resetting and lowering the hot tire pressure target, which, you know, may have been perfect in the winter, but may not be right for the summer conditions. So, based on track temperature, that's the first variable that makes a huge difference. So you have to always keep that in the back of your mind. Readjust your hot targets based on the track temperature. So you should always track your track temperature.

Why does a green track want higher pressure?

The next very important variable, it's the actual grip condition of the track. So if the track is really grippy, most of the cases you can run lower tire pressure targets, whereas when the track is very slippery you should run higher tire pressure targets.

Now don't ask me exactly why that's the case, but it just seems to be the rule of thumb over the years. You know, it might sound counterintuitive, because when you have the track being very slippery and kind of green, in a way you're like sliding quite a bit more than in a grippy track. So you may be like, oh, but this should be the opposite, right? You know, you should run lower pressures with green tracks, and higher pressures with grippy tracks, because you slide less. But just somehow it's not really the case.

You know, what I believe is that the reason maybe is because when the grip is high on the track, you're going to carry more speeds. The tires are going to actually be stressed more because you have more speed, more effort on the tires. Imagine if the track is three seconds faster than a green day, you're going to carry way more speed, and therefore the tires are actually going to heat up more, not because they're sliding, but they're actually doing more work. And so they actually need to have a lower pressure for that. Otherwise, they overheat. You know what I mean? So, and that's the opposite in very green tracks. That's why you may have to run a little higher tire pressures, because you anyways are not going to be able to carry a lot of speed into the corners, because the track is green. It's going to be sliding. You know, that's why when you have really green tracks, you're going to have to run pretty high tire pressures, which may be a little bit unusual. But yeah, that may be the only way to actually extrapolate some performance.

So yeah, this rule of thumb, you gotta stamp it in your brain. Green tracks, higher pressures. Really grippy tracks, you can go low pressures. And that's, by the way, I remember when we have had really soft tires and really high grip, in 2010, 11, 12, literally 15 years ago, when the compounds were super soft. I remember that, okay, not only the compounds were soft, which at the end of the day they need to have a low tire pressure, but at the same time when the grip level was so high, given the same compound, you would go very low on the tire pressure. And that was the only way to really keep the consistent performance throughout the whole session. And if you didn't do it, just, you weren't fast. And yeah, that just seems to be the case. So that's my rule of thumb. It really works in my case, and I hope it works for your case too.

Harder compound up, softer compound down

The next condition you really want to be mindful about is the compound of the tires, okay? And it's not just the compound. It actually depends from tire to tire in terms of brand, because at the end of the day, every tire has its own DNA, in terms of grip level, in terms of dimensions, in terms of, like, literally the tread of the tire. So it's not really coming down to compound. It's not really an apple to apple comparison. It's a bit more complicated than that. And I don't expect you to find all the answers that you need, but I even don't have all the answers. So I'm not going to pretend that I know all the answers.

The only thing I'm saying is that the rule of thumb is that when you have a harder compound tire, which is basically less grip in general, you'll need to be running higher tire pressures. So if the normal target is 0.90 bar, well, maybe with a harder compound you'll need to run 0.95, or 1 bar, or 1.1 bar. It really depends quite a lot, and you need to be flexible and adapt to that. Whereas if you have a really soft compound, you may have to run very low tire pressures, like with LeCont, I remember we were running 0.25 or 0.30 even. I'm not saying that's the right thing to do, but in some cases it worked really well.

Whereas I'm sure it wouldn't have worked if we drove with MG tires or with Maxxis, you know, running with that low a pressure, even though I never really drove with Maxxis, and I would like to try once. But yeah, over my whole career, when you run with the softer compounds, you need to run with lower pressures. When you drive with harder compounds, with less grip in general, you will have to run with higher tire pressure.

Wet: how much water is on the track?

Then the final variable that you have to consider, of course, if the track is wet, is the actual amount of rain on the track. I know this should have its own guide, but let's just include it here for a second. If there's a lot of standing water, you have to run higher pressures. If the track has very little water on the track, you're going to run lower pressures. If the track is just like on the edge between dry and wet, and you can see a drying up line, then you're going to be super low in the tire pressures.

So again, that makes a big difference if you have the wrong tire pressures when the track is wet, either too low when the track is very wet, you're going to suffer, or too high when the track is drying up, and you're going to suffer too. So, and the tires as well. So you want to be really fast and clever at adapting those conditions. You'll see that it won't be that important to actually change other stuff on the kart, like sprockets, like setups. What actually going to play out the most is nailing the right tire pressures for all conditions. I feel that's really what is going to extrapolate the most amount of performance, even though again, it's more of an art than a science.

Art, science, and the question I ask every driver

So it's not really easy to outsource to somebody with not enough experience, or to just, like, have AI doing it for you, because the reality is that it still comes down massively to experience. And yeah, you can have a look at data and take decisions based on data. But the reality is that data is most of the time rearward looking. And so you won't have real value from what you actually have to do in the moment, when you're sitting in the pit lane and you have to choose last minute what kind of tire pressures to run.

So normally I like to say to myself, and even to the drivers, I'm always asking them the question. I'm like, okay, let's say the tire pressure is not going to be perfect, what do you want? Would you rather, you know, be quicker in the first laps and drop off by the end, or would you be struggling more in the beginning and, you know, and being faster at the end, stuff like that? Or, like, would you prefer it to be faster when the track is full wet, but if it dries up, you've got to struggle a bit? Or vice versa, you're going to struggle a bit when the track is full wet, but get much faster when the track is going to dry up. So, you know, the perfect pressure doesn't exist, as well as the perfect setup and the perfect lap.

So I believe that the real goal, as a team manager, as a mechanic, as a coach, as a driver, is to get as close as possible to that sweet spot, to get perfection, I would say. But you will never really nail it. It's like, you may feel like you've nailed it, but you could have always been a little bit lower, a little bit higher, you know. In hindsight it's always easy, but in that moment you need to have the right state of mind, and ideally the right expertise behind your back, to take the right decision.

And again, this is going to come down a lot to, um, to experience, even though data for sure helps a lot. If you can track performance, and track the tire pressures you run in past races, in past sessions, with different track temperatures, with different compounds, for sure this is going to massively help you, then if you're doing everything blindly and just letting it down to chance.

So, of course, I'm sure in F1 they are not doing things randomly. They're doing everything very, you know, scientifically, very precisely. That's ideally what we are going to be doing in the future, with you guys, with myself, and yeah, with all the drivers that I'll be working with, but as well as you guys simply driving on your own.

The feeling of nailing the optimal tire pressure is gorgeous, it's an amazing feeling. But also the feeling when you get them wrong is quite awful. So yeah, it would be awesome to never really have that feeling. But unfortunately, sometimes you may get the perfect tire pressure, like, oh yeah, I've just nailed the conditions, but then it starts to rain, and you're like, oh, I'm gonna be too low for that. Or vice versa, you're perfect for the track condition, but then all of a sudden it dries up super quickly, and you're like, oh, I'm gonna be too high for that. And so you have to look for wet patches on the straight, so you can cool the tires down a bit.

But of course, as I said, it's a moving target. You can't get the perfect tire pressure for every single lap, every single session. It's just not possible. The goal is to get as close to that perfection as possible. And you'll see that if you're applying this rule of thumb, and you combine that with some strategic and scientific approach, you will get there.

I hope this was useful. Make sure you sign up to PURPL, there's the free trial, you can get started with that. But also, make sure you join the six-month training program if you want to elevate your karting experience and become a world champion, just as I managed to achieve in 2013. I'll see you.