How to Drive a Kart in the Wet: Braking and Wet Data

By Alessio Lorandi, 2013 CIK-FIA World Champion, KF-Junior. What is in here comes from my own wet races, from Mini to KZ, and from the wet data I go through with my drivers at BabyRace.

Everybody tells you to be careful on the brakes in the rain. I think it’s the opposite.

As 99.9% of us drivers, I sucked the first few times I drove in the wet. The kart was driving me, not me driving the kart. I was quite a few seconds off, and that felt so humiliating to me.

After a few traumatic wet races in Mini, I got my very first win in the wet in the Trofeo Margutti, back in 2010. Today driving in the wet is my favourite thing to do. Any day I can go out in the rain is a day of pure pleasure.

So here I want to tell you how the driving changes when the track is wet. And I start from the brakes, because that is where most drivers get it wrong.

The lines and the kerbs, the body, and the gamble on slicks have their own articles: my wet driving tips, weight transfer in the wet and when to gamble on slicks. I don’t repeat them here.

Should you brake earlier and softer in the wet?

No.

Everybody thinks that in the rain you have to drive very carefully and brake very cautiously. That couldn’t be further from the truth. In the wet you need to be even more aggressive on the brakes, and even more skilled on the brakes, than in the dry.

I know what you’re going to hear in the paddock. Most coaches and mechanics will tell you: in the wet be careful on the brakes, brake a bit earlier, brake a bit softer. I keep hearing this, and it makes me cringe. Because that is the way to be mediocre.

Think about the dry for a second. In the dry there is a lot of grip, so yes, you need to brake late and hard, but the grip is kind of going to make you stop anyway. In the wet nothing stops you. You have to stop the kart yourself, and you have to use the brakes to do it.

I won many races in the wet, one of them an Italian championship round with almost 15 or 16 seconds on the driver in P2. I’m not telling you this to show off. I’m telling you because the gap you can make on the brakes in the wet is that big.

Why do you brake more in the wet than in the dry?

Because your minimum speed is so much lower.

Take an average track in Italy. On slicks you have two, three maximum major braking spots. Most of the other corners are medium or high speed, where you don’t brake at all or you just tap the brakes.

In the wet, all those medium speed corners become real heavy braking corners.

Why? Yes, you arrive with a lower speed, because you couldn’t carry the speed out of the previous corner. That’s why you are 12, 15 or even 20 seconds slower in the wet, depending on the track, the asphalt and how much rubber is layered on it. But the minimum speed drops even more. At a track like Lonato you have about 15 to 20 km/h less at the apex between wet and slicks.

And how do you get down to that minimum speed? You’re not going to lift super early on the straight and roll into the corner. You have to use the brakes, and you use them more, and for longer, than in the dry.

So in the wet the two places where you spend the most time are on the brakes and in the mid corner. And you will see with your own eyes how big the difference is between an efficient late braker and an inefficient early braker.

In the wet, all the medium speed corners become heavy braking corners.

What does braking efficiently in the wet mean?

It means that how hard you hit the pedal is only one part. The other part is how long you hold it.

You can stomp the brakes once, very hard, and come off right away. You won’t be efficient. In that case you’d probably be better off braking 20% less in terms of peak, and then holding the brakes for longer, so you stop the kart properly.

So I don’t look only at the maximum braking force, and not even at how late you brake. I look at how long you trail the brakes into the apex.

Trailing the brakes into the apex is really the way to go. You can’t expect to be fast in the wet by tapping the brakes and coming off. You smash them, and then you hold them deep into the apex.

And you push yourself to brake as late as possible. But late on its own isn’t enough. You need to match it with braking efficiently. If you want the full technique, I explain it in the art of trail braking.

Why does the kart understeer mid corner in the wet?

Most of the time, because you didn’t use the brakes properly on the entry.

Let me explain. Look at how much steering wheel you have to use in the wet. It’s way more than in the dry. There’s a reason. You arrive with less speed, so there is less weight transfer, and you have very little momentum into the corner. When you don’t have momentum, the kart does not rotate.

So the momentum is not by your side. What is left? The brakes.

When you brake deep and hold the brakes, the weight moves from the back to the front. You can call it pitch, or dive. The front lowers down and the rear kind of lifts up. In formula cars they call that rake, and it is super important there. On the kart it loads the front and it gives you the rotation.

So the brakes in the wet are not only for stopping. They keep the front loaded until the apex, and that is what turns the kart. If you come off the brakes early, the front is light, and you sit there in the mid corner with the steering turned, waiting.

One thing about the steering. Even in the wet, which needs way more steering than the dry, you still don’t want to turn max. With the Ackermann effect, at some point turning more makes you turn less.

Where on the track do you brake in the wet?

Outside of the rubber. This is the core thing.

If you brake where everybody brakes on the slicks, you are on the rubber. And rubber in the rain becomes soap. You brake hard there and you go straight, or you spin.

That is where the bad advice comes from, by the way. The driver makes the first mistake, which is braking on the rubber. He goes straight. So somebody tells him to brake softer. But braking soft on the rubber is just putting a bandage. The core problem is that he is not braking on the right piece of track.

I hear it from drivers too. “But Alessio, you told me to brake hard, and I keep spinning when I do that.” Of course. You’re applying the right technique in the wrong place. It’s like trying to ski in the ocean. You ski on the mountains, and you surf in the ocean.

So where is the rubber? Everybody opens up the corner as much as possible in the dry, so the rubber line is at the outside edge of the track. Your braking goes in the middle of the track, or even tighter to the inside. It depends where the rubber is layered, so pay attention to that.

I know at some point you will have to cross the rubber line. Ideally you join it when you are already rotated and mostly into the mid corner, and not on the brakes. And on the exit you can’t go 100% on and off the gas. You modulate the throttle, especially when you cross the rubber.

The rest about the rubber, the kerbs and the exits is in my wet driving tips.

How long do you hold the brakes in a Mini, a junior and a KZ?

It changes with the category, because the line changes.

60 Mini. Most of the time you have to open up the lines in the mid corner. The torque is so low that you need to keep up the RPMs and the momentum. You can’t count on the exit speed. But still, the braking is key.

Single speed juniors and seniors. With an X30 or a Rotax, junior or senior, there is quite a lot of torque, so you may have to cut over the kerbs and make tighter lines. You may lose a little bit of minimum speed, but you make so much less distance that it pays the price. Remember, time is distance divided by speed. It pays off most in sequences of corners in opposite directions, where you don’t have long straights in between.

When you go for the kerb, the braking is almost in a straight line. You brake really hard until the kerb, and when you’re on the kerb you come off the brakes. And you have to hook that kerb in the right way. If you hook it too early you get pushed out wide. If you come off the brakes too early you overshoot it, you end up on the rubber and you lose a ton of time. So hold the brakes until the kerb.

And look at the kerb before you use it. If it has just rained and there’s a big puddle over it, it may make no sense to go there, even if it makes sense in the dry.

KZ. With the shifter you can really smash the brakes and lock the tyres. You drive in a constant state of sliding. That is also how you warm up the wet tyres, which are normally very hard and take a lot of time to get any temperature. And you can hold the brakes into the apex, because you have the gears. In the wet there’s no real grip, so you glue yourself to the engine brake. When you go down from second to first you feel it stopping you so much.

How I split the two wet lines by category is in weight transfer in the wet.

Why do the brakes feel dead in the rain?

Because they are cold.

The brakes have their own “window” like everything else on the kart. Normally they get there on their own. Except when it rains heavily. Then the disc cools down too much down the straights, with the cold air and all the standing water. That’s why drivers complain in the wet that the kart doesn’t brake at times. They don’t feel the bite.

And it’s strange if you think about it, because in the wet you spend a bigger part of the lap on the brakes than in the dry. It’s still not enough to keep the disc hot.

I really feel the difference. When the disc is cold it’s a nightmare. I feel it even on slicks. You go out of the pit lane, and even on a summer day it may take one or two laps to get the brakes to temperature.

So my suggestion is a brake cover. You can make it yourself with the plastic of your old number plates, going around the disc. You want it especially in heavy rain.

But watch out. As soon as it stops raining heavily, take it off right away. Otherwise you cook the brakes, and when they’re too hot they don’t brake well either.

One small detail on the pedal too. I’m very picky about the grip on the pedals. I put some scratch tape on the pedal so the shoe doesn’t slip when it’s wet. In the rain it gives you more feeling from a firm pedal.

Is your data useless in the wet?

I used to think so.

When you drive in the wet you’re often almost alone on the track. Maybe you don’t have teammates to compare against. The track changes every single session, the standing water changes, the grip changes. So there’s no real reference lap. I felt like, what’s the point of even charging my logger?

Now I look at it differently. In the wet your reference is yourself, in that session.

On PURPL I look at the mini sectors heat map. For every lap you see the gap from each mini sector to your fastest one. So you see on which lap you got the best mini sector, and then you go and look at what you did there. Maybe on that lap you tried to go super wide, and the delta time says you gained one tenth.

But be careful with one thing. Speed is just 50% of the equation. The rest is the distance. This is what I always show my drivers at BabyRace. A line can carry more speed and still be worse, because you make too many meters. So you always match the speed with the distance. If your speed is the same and you’re just doing more meters, it’s a no-brainer to try a tighter line.

And it’s not black and white, full wide or full tight on the kerb. Some corners you have to drive in between.

What do you do with it? The next session will not be the same. If it’s a bit drier, you brake a bit later and carry more speed. If it’s wetter, you brake a bit earlier. But you go out knowing which lines worked in the conditions you just drove. And you memorise it by condition. Next time the track is that wet, you start from those lines.

What else does the wet data show you?

Quite a lot. This is what I look at, and what it normally tells me.

Tyre pressures. You see the grip in the friction circle and in the grip load index, so you can compare two runs with a quite large change of pressure. As a rule of thumb, with a lot of standing water you run higher pressures, and with very little water on the track you run lower. When there’s a drying line, that’s a different game, and I cover it in when to gamble on slicks.

Sprocket. The data won’t tell you what to do. It shows you what you did in other sessions with other sprockets, and the difference is quite clear.

Water temperature. Normally the water gets very cold in the wet. It doesn’t keep up the temperature.

Carburation. You can’t run the same carburation between the wet and the dry. You need to lean it out massively. Every time you brake and wait to go on the gas, the engine fills with fuel that doesn’t get burned. So it goes rich. You lose in the mid range, and at the bottom the response feels dirty, delayed, laggy. On an X30 it’s easy, you close it with the two screws. On other engines have the jets at hand. More in my carburation tips.

All of this works with the data you’re already recording.

Should you add rear grip in the wet?

Everybody wants to add rear grip in the wet. I kind of disagree.

There’s this common fallacy in karting that it’s the rear that defines your performance in the wet. Yes, you lack rear grip too. But most of the time in the wet you’re lacking front grip. If you have too much rear and not enough front, you get so much understeer, the kart doesn’t rotate, and you’re not fast.

My theory is that the less grip there is on the track, the more rotation you need. It’s counterintuitive, I know.

That’s why in the wet I love to run the seat far at the front and quite high, to create extra weight transfer and load on the tyres. And I soften the seat instead of stiffening it. The body part and the seat are explained in weight transfer in the wet.

How do you get better in the wet?

You drive in it. A lot.

When I was so far off in the rain as a kid, I understood that I wasn’t good enough yet in the wet, and that I needed more track time than my rivals to close the gap. Laps and laps, day in and day out, until I got comfortable finding the wet lines and pushing despite the slippery conditions.

I see the same with the kids today. Some of them are afraid of the wet. They drive so careful because they’re not familiar with low grip. If your kid is like that, it means he needs way more driving time in the wet.

My number is at least 50 days a year in the rain. It seems like a lot. But it’s about four days a month.

And when you’re out there, experiment with the lines. It’s never the same wet. There is never the exact same standing water as another day, so the line that worked last time is only where you start from.

If you want to do it in order, this is how I’d approach a wet session:

1. Find where the rubber is layered, and move your braking off it, to the middle of the track or tighter.
2. Brake hard, and brake late.
3. Hold the brakes into the apex, or until the kerb if you’re cutting over it.
4. Join the rubber only when the kart is already rotated.
5. Modulate the throttle on the exit, especially when you cross the rubber.
6. After the session, look at your best mini sectors and see which line you took there.

Next time it rains, don’t stay in the awning. Go out, pick one corner, move your braking off the rubber and hold the brakes until the apex. Then look at that mini sector.

Frequently asked questions

Should you brake earlier in the wet in karting?

Not as a rule. In the wet you need to be a better braker than in the dry: brake late, and hold the brakes into the apex. If the track gets wetter from one session to the next you may brake a bit earlier, and if it dries a bit later.

Why does my kart go straight when I brake hard in the rain?

Most likely you are braking on the rubber, where everybody brakes on slicks. Braking softer there is just a bandage. Move your braking to the middle of the track or tighter, off the rubber line.

Why does my kart understeer in the wet?

You arrive with little momentum, so the kart does not rotate on its own. Mid corner understeer in the wet mostly comes from not using the brakes properly on the entry. Holding the brakes until the apex keeps the front loaded and gives you the rotation.

Do I need a brake disc cover in the rain?

In heavy rain I suggest it. The disc cools down too much on the straights and you lose the bite. You can make a cover from the plastic of old number plates. Take it off as soon as it stops raining heavily, or you cook the brakes.

Is kart telemetry useful in the wet?

Yes. There is no reference lap from another day, so you compare your own mini sectors in the same session to see which line worked. You can also read your grip against the tyre pressures, the RPMs, the water temperature and the exhaust temperature.