Weight Transfer in a Kart: How Rotation Is Actually Generated

By Alessio Lorandi, 2013 CIK-FIA World Champion, KF-Junior. What is here comes from my own karting, my first Formula 3 season in 2015 and what I tell my drivers.

What is weight transfer, and why does it decide how your kart rotates?

Alright, let’s talk about something that most beginner drivers overlook, but it’s absolutely crucial in karting: weight transfer.

This is one of those things that, once you get it, completely changes how you drive and how you approach corners.

You’ll start braking better, steering smoother, accelerating more aggressively, all by using the weight of your kart (and your body) the right way.

Let me break it down for you.

What is weight transfer in a kart?

So let’s start by stating this: when you accelerate, brake or turn, the weight of your kart shifts around.

Simple, right?

But here’s the thing: how that weight moves affects how much grip your tyres have.

If you overload a tyre with too much weight, it’ll struggle. If there’s not enough weight, it won’t grip properly either.

The trick is finding that sweet spot. And that’s where experience comes into place.

You have to think about it. The kart is just a piece of tube connected to the wheels, and the wheels are the only thing touching the ground. The tube is highly flexible. The axle is highly flexible. The seat is highly flexible.

And all these flexibilities are highly affected by the driver and his posture.

So in a kart, weight transfer is not only the chassis. It is you as well.

Why does a kart need to lift the inside rear wheel?

Remember, in a kart we do not have a differential. Formula cars and GT cars have one. We are relying only on the rear axle.

And if the rear axle is flat, if it is not lifting up the inside rear tyre, you are not rotating the kart as well.

The kart rotates more when you have three wheels touching the ground and one lifted up than when you have four wheels touching the ground. I have experienced this a lot in my life.

So when the inside rear lifts, is it more grip or less grip? Neither of the two. You are going to have more rotation. That’s it.

And it is not really the extra load on the outside tyres. It is more the unload on the inside rear tyre. You want to lift it up, even by just a fraction.

What happens when it stays down? Let’s say you are in the mid corner at the end of a heavy braking zone and the two rear wheels are glued to the ground. Maybe you did not carry enough speed. Maybe your seat is too stiff, or your axle is too stiff.

Then you get understeer. A rear push. You are still turning the wheel, so you cannot pick up the throttle. If the two words are still a bit blurry, I explain what understeer and oversteer are in a separate guide.

That is the whole reason weight transfer matters in a kart. It is how you get that little micro lift in the mid corner.

Does more load on a tyre mean more grip?

Yes, but not as much as you think. Everything starts from tyre load sensitivity.

In simple terms, when you double the load on a tyre, you do not double its grip. Grip increases sub-linearly.

Let me give you an example with the rear tyres. The units are just an example, not something I measured.

So the total load on the rear axle stayed the same, but the total grip dropped by 5%.

That is what weight transfer does. With more weight transfer, the total grip available is less. With less weight transfer, it is more.

Does that mean you always want less? No.

Sometimes you will not care about that, because in that moment your only care is to rotate the kart as fast as possible and get on the gas earlier.

Karting is really an art more than a science. Sometimes you have to do X, sometimes you have to do Y. That is why you need to be a grip hunter and feel what the kart needs in that session.

What is rotation, and why is it lap time?

There are many ways to define rotation. My simple way is this: taking the kart from pointing in one direction on the entry to pointing in the other direction on the exit, as quickly as possible.

Imagine you had an arrow coming out of the centre of your kart, going one metre ahead. In a 180 degree hairpin you want to take that arrow from one direction to the opposite one in as little time as you can, without losing the kart.

The more time you spend waiting for the kart to rotate in the middle of the corner, the slower you are. Period. The less time you spend rotating, the earlier you go on the throttle.

And I still see it to this day in karting. It is so easy to make the kart predictable and very balanced. But a very balanced kart, most of the time, is not a faster kart. You have to wait in the middle of the corner for the rotation to come.

Every hundredth of a second of extra time to rotate the kart counts. If we are talking about 12 corners, that’s 1.2 tenths lost over a full lap.

And when we talk about rotating the kart with the weight, we are talking about weight transfer. It is the same thing seen from the other side.

Where in the corner you want that rotation is a different question. I went through it in entry against exit, where do you want to rotate.

Why could Albon not drive Verstappen’s car?

One of the masters of rotation is Max Verstappen. You can see it in his onboard videos. He creates as much rotation as he needs with his driving, but he also really enjoys a car with a lot of rotation.

Alex Albon has said in interviews that Max’s car is super pointy on the front. Max requires such a pointy car from his engineers that it is hard for his teammates to even drive it.

And it’s not just Max. Michael Schumacher, Ayrton Senna. You see the pattern.

But you still have to drive it. I had conversations with engineers in the past, and they were like: not always the fastest car in theory is the fastest car on track.

I am not saying the others do not have the skills. They are just not used to driving such a pointy car from an early age.

It is the same principle in karting. That’s why I love driving with my seat very far to the front, even though in many cases it’s not super fast, because I end up sliding too much on the rear.

What did my mechanic make me do at eleven?

Thankfully, my mechanic when I was little, when I was like 11, taught me how to drive a high rotation kart.

I was like: mate, but it’s sliding. Scivola dietro, that’s what I was telling him in Italian. It slides at the back.

And he was like: no worries, just keep driving.

He was right. It was tricky at first, but I got used to driving that way.

That’s why I prefer my drivers to have the seat slightly more forward rather than more backwards. They can always learn how to drive an oversteery kart by doing so.

If you always drive with understeer, then the moment you go searching for more rotation, you are not going to be used to it. You can’t just say: okay, let’s create the rotation now.

And whenever the kart is snapping and sliding on the rear, maybe it’s not ideal in that specific moment, but you are developing car control. It’s almost like you’re driving on ice every single lap.

It has to start from as early an age as possible. If you start at 16, it’s a bit too late in my opinion.

Why does grip always arrive at the rear first?

Think about it. Every time the track goes from green to grippy, you always pick up more rear than front. Always.

Because the rear tyres are wider than the front ones. If the track gives you, let’s say, 2% more grip, the rear is going to pick up more of it than the front.

So the kart goes towards understeer. And 99% of the teams and drivers are not going to change the seat position between a green track and a grippy track. Most of the time they change axles, they change something on the front.

But the seat is the weight distribution, at the end of the day. If you want more rotation, you put the seat more forward. Instead of having, let’s say, 70 on the rear and 30 on the front, you go to 60 and 40, or even 55 and 45. Those are numbers to give you the idea.

You still have a little more weight on the rear, but you have way more on the front. The front gets stronger and the rear loosens up.

If you have so much understeer that you are turning and turning, go forward with the seat at least one or two centimetres. Try that and you’ll see the kart change drastically.

I go deeper on this in the importance of seat positioning.

How do the brakes move the weight?

When you’re braking, you want to hit it hard, late, but controlled. Not sloppy.

The goal is to load the front tyres just enough to bite into the track, without unsettling the whole kart causing excessive weight transfer to the front.

Every time you brake, the weight moves forward and it moves down a bit. It’s inevitable.

How do I know? Sometimes I’ve had the chance of driving my KZ with a very low front bumper, maybe by mistake. And when I was braking hard, I could feel the front bumper touching the ground.

So these are the rules of thumb. Aggressive braking or corner entry generates a lot of weight transfer to the front, increasing rotation. Soft braking and slow entries generate more understeer, with less weight transfer to the front and therefore less rotation.

That is why rotating with the brakes is the number one way to get rotation while you drive.

I always ask my drivers: so you have understeer. We cannot change the setup while we’re driving. What can you do with your pedals? You can get more rotation with the brakes. All right, then go out and do it.

In the hairpins you can make a massive difference by braking later, harder, holding the brakes a bit longer. I wrote more about that in the art of trail braking.

In a fast corner where you do not use the brakes, you cannot do that. There you can only use the speed and the steering.

Not sure if your understeer comes from the kart or from your pedals? Send me an onboard. I look at your braking and your turning points corner by corner in an onboard review.

Where do you come off the brakes in a kart?

In a car, you hold the brakes all the way to the apex. I learned that in Formula 3.

It was 2015, my first year. We were on the simulator preparing for the first race, and my engineer Peter showed me the telemetry of Daniil Kvyat at Hockenheim. It was data shared by Volkswagen, because we were using the Volkswagen engine.

He showed me the second corner and the fourth corner, the two hairpins. You hold the brakes up until the apex, otherwise you lose the front and the car doesn’t turn. No dead zone.

I was doing a tiny bit of coasting in the middle of the corner, which is a very common mistake for drivers coming from karts. When I tried it his way, the car felt so much more pitched on the front and I got way more rotation.

In a kart it is not exactly the same. You want to be off the brakes slightly before the apex. There is always a little transition, like 0.1 second or so, where you do a tiny bit of rolling.

Why? A car has a differential and suspension. A kart has an axle, and you’ve got to let that axle flex.

You want the kart to complete the rotation on three wheels before you get on the gas. If you go too early, it’s just going to bounce and push into understeer.

Why does a kart not rotate when you drive it slowly?

The speed you carry changes the rotation. You’ll be like: what do you mean, Alessio?

Well, think about running in an engine. I guess all of you have done it at least once. You have to be at like 50% of the speed on the straights, releasing the gas every two or three seconds.

So you are not fast in the corners either. And what do you feel? The kart has no rotation. Absolutely nothing. It is so understeery.

That is the lesson. When you carry the speed and attack the corners, the kart rotates on its own way more than if you did not push.

It is the same thing with the inside rear. The axle stays stiff unless you carry a lot of speed into the corner, and the G forces increase the lift of the inside rear.

So you have a massive effect on the rotation just with the speed that you carry.

Should you lean in or lean out?

You can use your body to help control weight transfer, but it doesn’t mean you should overly obsess about it.

In a car you cannot do it at all. You are strapped in. And let’s say the car is 800 kilos and you are 70: you are about 8% of the weight. In a kart your body counts much more.

Moving your body outside the corner gives more weight to the outside wheels, making the inner rear tyre lift up a bit, generating more rotation.

Moving your body inside the corner, the “watching the apex” style or the “moto gp” style, reduces the weight transfer to the outside. It grips up the rear, so you have more rear stability.

Sometimes that causes lots of understeer, when the track’s got lots of grip and the rear is already very strong.

So not enough rotation, lean out a little bit. In the mid corner, not on the entry. Too much rotation, lean in. But don’t overdo that. Just do what you need.

The professional drivers I have seen mostly lean inwards rather than outwards. They race in high grip, on soft tyres, and with too much weight transfer you may even risk going on two wheels.

And my personal take: when the kart is really balanced, you should not lean too much either in or out. The body is the last thing you use, once you have run out of options.

Does a soft seat or a stiff seat give more weight transfer?

Another important thing I learned over the years is that the stiffness of your seat changes the way weight moves.

• A softer seat lets the kart flex more, which gives you more weight transfer, making the kart more free on the rear.
• A stiffer seat will limit movement, making the kart more stable, but usually a little trickier to rotate.

So which one is faster? Neither. There’s no such thing as a faster seat. The question is: do you need the weight transfer or not?

I went to visit Steve Tillett in England and we talked about exactly this. With a stiff seat, the inside rear wheel lifts up less. With a softer seat it lifts up easier.

He told me why they started making very soft seats. The tyres got softer and softer, there was so much rubber on the tarmac, and the only way to free the kart up was a soft seat that would generate the weight transfer.

I keep different rigidities of Tillett seat. If there’s a lot of grip and I want to free the kart up, I go with the softer one, the VTi. If the track is super slippery and I want more support on both rear wheels, the stiffer one, the T. In between, the VG, which in KZ is the one that works best for me.

And it depends on the driver. Tall, heavy drivers already have a lot of weight transfer themselves, so they normally work better with a stiffer seat. Small kids have less weight to transfer, so they normally work better with a softer one.

But I wouldn’t play too much with it. Knowing when to use which seat is part of dialling in your kart properly. The full version is in soft seats against hard seats.

How does the steering change weight transfer?

Any time you turn the steering wheel, you are changing the weight transfer. With the geometry of the front, when you turn to the right you are loading the outside tyres, the left ones.

That is why on a clockwise circuit, where most of the corners are right-handers, the left tyres heat up way more than the right ones.

So can you turn more to get more rotation? A tiny bit, in the mid corner, yes. But there is a limit, and it is my last choice.

In a kart we do not have suspension, and the steering geometry is very aggressive. If you are too aggressive in the initial turn in, you make the whole corner unstable and you overheat the tyres.

And remember that the steering acts as a brake. It is friction. Especially with the lower powered karts, like 60 Mini or juniors, you do not have a lot of horsepower, and the more your tyres are turned on the exit, the more of it you kill.

So, same as with the brakes: don’t just dirtily turn the wheel. Turn smoothly, use your body, and manage the balance of the kart through the corner.

If you need to turn that much because the kart is not turning, it’s a setup problem. Talk to your mechanic. More on the driving side in smooth is fast.

Why does weight transfer matter more in the wet?

Weight transfer is probably the number one thing you’ll have to master in the rain.

There’s this common fallacy in karting that it’s the rear that defines your performance in the wet. It’s not really true. Most of the time in the wet we are lacking front grip. If you have too much rear and not enough front, the kart doesn’t rotate, you are still turning the wheel, and you cannot pick up the throttle.

So it is a bit counterintuitive. It would make sense to stiffen up the seat in the wet. But if you stiffen up the seat, you have less rotation. I actually like to soften the seat a lot whenever I drive in the wet.

I also love going with the seat far to the front in the wet, and quite high, to create extra weight transfer and load on the tyres. That is always a very good thing in my case.

And this is where the body helps. If you turn right, you throw your body to the left, to the outside. Especially when it starts to rain while you are already on the grid and you cannot change the setup.

But I wouldn’t want a driver who has to rely only on his body to rotate the kart. That’s a patch on the problem. A fast kart in the wet is almost rotating on its own.

How do you practise it? What I do with my drivers at BabyRace is ask them to sit in the kart in the tent. Turn to the right and push the body to the left, then the opposite. On the ground you can feel the kart flexing, and you can see the inside tyre lifting.

Get used to it there. Then replicate it on track, without pressure.

What should you ask yourself in every session?

Next time you’re on track, start asking yourself:

• Am I shifting the weight the right way during each phase of the corner?
• Am I giving too much or too little load to the tyres?
• Can I help the kart rotate better with my body?

Trust me, this mindset shift alone will already make a huge difference in your lap times and overall consistency.

Weight transfer isn’t some advanced driving theory.

It’s a basic part of kart control that you can feel (and improve) from day one.

Once you start understanding how your inputs move the kart’s weight, your driving becomes more refined, more in control, and a lot quicker.

And if the kart is not rotating in that specific session, you rotate it with the brakes, or with the speed, or with the weight transfer, or with the steering.

Just Senndit,
Alessio

Frequently asked questions

What is weight transfer in karting?

When you accelerate, brake or turn, the weight of your kart shifts around. How that weight moves affects how much grip your tyres have. In a kart the driver is a big part of it, because the tube, the axle and the seat all flex with the driver and his posture.

Why does the inside rear wheel lift on a kart?

A kart has no differential, so the rear axle is stiff. The kart rotates more with three wheels touching the ground and one lifted up than with four on the ground. Weight transfer to the outside unloads the inside rear tyre, and that little lift is what gives you rotation.

Should you lean in or lean out in a kart?

Lean out a little in the mid corner if you do not have enough rotation, because it helps the inside rear lift. Lean in if you have too much, because it keeps the rear more planted. When the kart is really balanced you should not lean too much either in or out.

Does a softer seat give more weight transfer?

Yes. A softer seat creates more weight transfer and the inside rear wheel lifts up easier, so you get more rotation. A stiffer seat keeps the rear wheels more planted. There is no such thing as a faster seat, it depends on whether you need the weight transfer or not.

Why do you want more weight transfer in the wet?

Because most of the time in the wet you are lacking front grip and rotation. More weight transfer helps the inside rear lift so the kart rotates and you can pick up the throttle. That is why I soften the seat in the wet and run it higher and further forward.