Kart Tire Management: Pressures, Warm Up and Tire Life

By Alessio Lorandi, 2013 CIK-FIA World Champion, KF-Junior. What is in here comes from my own years of racing and from what I see with the drivers in my team.

Are you fast for two laps and then the kart drops off? Or slow at the start and fast when the race is almost over?

Both are tire management. And it’s not only something you do with the gauge in the tent. A big part of it you do with your hands and your feet, from the moment you leave the pits. So let’s go through it: how to warm the tires, where to put the pressures when the conditions change, why new tires can make you slower, and how to keep the tire alive until the last lap.

What is tire management on a kart?

For me it’s two things that you have to nail at the same time: the tire temperature and the tire pressure.

Every tire has an optimal operating range. Once the temperature stabilises in there, your job is to drive smoothly inside it. If you go beyond it, the tires overheat and you lose performance in the last stages of the race. If you never get there, you’re driving on something that feels like ice.

And listen, you are the only one responsible for your tire temperatures. Your mechanic sets the pressures. But what happens to the tire from the pit exit to the flag, that’s on you.

Is it tire pressure or tire temperature that gives you grip?

Mostly temperature. More temperature gives you more grip, more grip gives you more speed, and more speed puts more temperature in the tire. It’s a cycle that feeds itself.

So when I look at a setup, I start from the tires. Are the fronts overheating? The rears? Or are they not getting hot enough? The temperature tells me more than the pressure does.

How does a tire get hot? Under load. Corners are high load. A straight is almost zero load. That’s why the tire heats up in the corners and cools down on the straights.

And don’t think pressure and temperature always move together. They are not that correlated. Sometimes a lower pressure makes the tire flex more, so it heats up more. With other compounds it’s the opposite. So you can’t assume, you have to test it on the tire you’re racing.

One more thing. Modern tires are harder, they last longer, and they are slow to generate temperature. So if your fastest lap always comes late, nine out of ten times it’s tire temperature, and raising the pressure is only a bandage for the first couple of laps.

How do you warm up kart tires without hurting them?

When I was racing, between 2012 and 2014, my mechanic used to tell me the same thing every time I went out: “Remember to warm up the tires, Alessio.” And he was right, because in 99% of the cases the tires need to be warmer on lap one than they are. Even with 60 degrees of track temperature, the first laps can be one second slower.

But there is warming a tire and there is sliding a tire. Warming is load and energy going in. Sliding is going beyond the slip angle. On cold tires with low pressures, sliding gives you graining: the inside of the tire is still cold and the outside is already too hot. You want to build the temperature from the inside to the outside.

So a few things I do, and a few I don’t:

• With fresh, soft, cold tires I bring them up progressively. I almost massage them.
• I don’t weave off the racing line. You collect pickup and dirt, and that cools the tire.
• The rears warm up easily. The fronts warm up from heavy braking, so I attack the entries and I stay gentle on the throttle.
• I don’t scrub the fronts with the steering.
• I stay off the curbs when the pressures are very low in the summer. I learned that one on a Formula 3 test day, with a puncture and blisters.

The goal is that both axles get to their peak together. If the fronts are behind, you have understeer for two or three laps, and by the time they arrive the rears are gone and you have oversteer.

And once the race starts, just push. I wrote about the full procedure in why your outlap decides your race.

How should tire pressure change with track temperature?

The rule of thumb is simple, and it works something like 90% of the time. Low track temperature, higher pressures. Very high track temperature, lower pressures.

So the first thing is: always measure the track temperature. Not the air, the track.

In Italy from July to September the asphalt can be around 65 degrees. And track temperatures above 60 are becoming the norm in the summer. On those days the target you used in spring doesn’t hold anymore. You have to lower it, and you have to experiment to find the new one.

Because the pressure you set cold is only a way to get somewhere. The target tire pressure hot, that’s what counts. And it varies from track to track. Tire pressures are always a moving target.

These are only directions. The number is the one you find on that track, on that day, with that tire.

Should you run lower or higher pressure when the track has more grip?

Lower. When the track is grippy you go lower, and when it’s slippery or green you go higher.

Don’t ask me exactly why. What I believe is this: more grip means more speed, and more speed means more work for the tire. Imagine the track is three seconds faster than on a green day. The tire is doing a completely different job. So if you leave the pressures where they were, they overheat.

I saw it between 2010 and 2012, when we had super soft compounds and a lot of grip. We were running very low pressures, because it was the only way to keep a consistent performance through the whole session.

The grip of the track changes during the weekend, sometimes during the day. I wrote about how to read it in track evolution in karting.

Does the compound change the pressure you run?

Yes. Harder compound, higher pressures. Softer compound, lower pressures.

In the cold months with very hard tires you have to run pretty high pressures. But you have to forget about those when you drive soft tires in the hot months. If you put winter pressures in a soft tire in the summer, you do the outlap and then you’re done.

And every tire has its own DNA. What works on one brand doesn’t transfer to another one, and I don’t have all the answers for every tire out there. You have to test the tire you are racing on.

I compare the two in soft vs hard kart tires.

What tire pressure do you run in the wet?

It depends on how much water there is.

With a lot of standing water, I go higher. With very little water, lower. And when a dry line is coming and you are still on wet tires, super low.

And if it dries more than you expected and you are too high? Look for the wet patches on the straight and drive through them. It cools the tires down.

The other question on a day like that is when to go to slicks. That one is in when to gamble on slicks.

Should race pressures be lower than qualifying pressures?

Yes. To win a 20 laps race you can’t really run on high tire pressures. Qualifying is three or four laps. The race is a different job, so you start quite a bit lower than you did in qualifying.

What happens if you pump them up to be fast early? You’re strong for a few laps, and then you get a severe drop in the second half. It feels like somebody pulled the hand brake after lap 10.

The price of low pressures is that you won’t feel as comfortable in the first laps. But you have to be fast despite that. Nobody sets the fastest lap of the race in the first few laps anyway.

So the question to ask yourself before every session is this one: do I want to be quicker in the first laps and drop off, or struggle a bit at the beginning and be faster at the end? At the end of the day the perfect pressure doesn’t exist. You choose where you want to be strong.

Where and when should you set your tire pressures?

Always in the same place, so the rims are always at the same temperature when you measure.

Think about the tent. It’s cold in the morning and hot at midday. In January or February there may be a heater in there. If you set the same number on a cold rim and on a warm rim, it’s not the same pressure, and you will get to a different hot pressure on track.

If you can’t keep the rim temperature consistent, use a calculator that converts the pressure on the rim temperature. There is a tire pressure calculator here on the site for cold starting pressures.

And check the pressures yourself, together with your mechanic. It happens that somebody is in a hurry and the tires go out on the wrong pressure. It’s your session, so it’s your responsibility too.

How do you find the right hot pressure on the day?

Honestly, tire pressures are more of an art than a science. And for me they matter more than sprockets and setup changes. So it’s worth having a method. This is how I would go through it:

1. Measure the track temperature before the session, and write it down with the compound you are on.
2. Set the pressures in the same place as always, so the rim temperature is consistent.
3. Come out a bit higher in the first session, and check the hot pressures when you come in.
4. Look at the lap time progression. Were you fast in the first laps and then dropped, or slow at the start and fast at the end?
5. Drop the pressures for the next session and compare the grip and the lap times with the session before.
6. If the tires overheat in the last few laps, run lower and reset your hot target for that day.
7. Log it. Track temperature, compound, average hot pressure and average tire temperatures, session by session.

Why the log? Because data is rearward looking. It tells you what happened, not what to do next. But when you come back to that track, or you find the same track temperature somewhere else, you are not starting from zero. I keep it in a simple sheet.

And don’t trust a target only because it’s written somewhere. A recommended hot pressure doesn’t hold on a hot, grippy summer day. On every new track you experiment, and you find the new target from the tire data and from how the lap times move.

Why can you be slower on new tires?

It happens more than people think. A few reasons I see:

• The pressure is wrong. Sometimes the pressure used to fit the tire on the rim is still in there, because somebody was in a hurry. It has happened in my team too. You come in, you lower it, but by then you have lost the peak of the tire.
• You have too much grip. If the kart feels on rails on used tires, on new tires it will probably be stuck and start hopping. It’s better to slide a little on the used set. On new tires you have to release some grip.
• The set is not a good one. Tires that were stored badly go through heat cycles every day and get harder.
• The circumferences don’t match.
• You didn’t push. New tires reward the drivers who use the extra grip. If you drive under the limit, the kart gets stuck and you go slower.

And before all of that, check if the others went slower too. If everybody did, it’s the track.

For the push lap itself, read my new tires and time attack tips.

How do you keep the tires alive over a long run?

You get them into the window, and then you stay smooth inside it.

The tires don’t only suffer when they’re cold. At the end of the race, if you are over pushing and sliding, you overheat them and you go beyond the optimal window. So I drive smoother to keep the temperatures consistent, especially on the rears.

When the track is above 60 degrees you have the grip straight away. But if you are aggressive, with your driving or with the setup, it fades. You do one or two fast laps and then you drop.

And look at the asphalt. Degradation is the abrasiveness of the track plus the temperature. Old tracks are usually more abrasive. Abrasive and hot together is a deadly combo. On some tracks a set lasts for days, on others it lasts a few sessions.

Basically, over one lap you want the peak. Over 25 laps you want consistency. If you have too much grip at the beginning, you’ll be stuck later in the run.

But be honest with yourself too. When the lap times fade during a stint, most of the time it’s the driver getting tired, not the kart.

What do the tires tell you after a session?

A lot, if you look at them before you look at anything else.

If they got too hot, you see blistering. If they stayed too cold, you see graining. If the fronts are graining and the rears are healthy, I free up the rear. If the inner edge of the fronts is consumed, there is too much camber. And too much toe overheats the fronts and costs you speed on the straights.

Then there is the balancing. Most mechanics only balance the fronts, but sometimes the rears are worse. And when the wear is high, the tires lose weight and they wear unevenly, so they need rebalancing almost every session. Check them on a proper balancing tool, not on the spindle of the kart. I mean, a vibrating tire costs you feeling, and without feeling you can’t manage anything.

The balance of the kart changes every session with the grip, the track and the tire wear. So this is a check you do every time, not once per weekend.

Next time you’re at the track, write down the track temperature, the compound and the hot pressures after every session, with one line on how the lap times moved from the first lap to the last. After a few days you will see your own pattern, and you will stop guessing.

Frequently asked questions

What tire pressure should I run on my kart?

There isn’t one number. What counts is the hot pressure, and the hot target changes with the track, the track temperature, the grip and the compound. Start a bit higher, compare the grip and the lap times, then go lower and compare again.

Do higher pressures warm up the tires faster?

They help in the first couple of laps, but it’s a bandage. In a race you pay for it with a drop in the second half. It’s better to warm the tires with your driving and start the race on lower pressures.

Why do my tires overheat at the end of the race?

Either you are over pushing and sliding, or the pressures were too high for that track temperature and that grip level. Drive smoother, especially on the rears, and run lower pressures in the next session.

Should I weave to warm up kart tires?

Not off the racing line. You pick up rubber and dirt, and that cools the tire down. Put load in the tires on the racing line, with hard braking for the fronts and a gentle throttle for the rears.

How often should kart tires be balanced?

When the tire wear is high, almost every session, because the tires lose weight and wear unevenly. And balance the rears too, not only the fronts.