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Why do kerbs make you spin?

We've all been there. You see the driver in front take huge chunks of kerb, so you try it and spin. Not to worry, there's a reason for that! In this video we will look at the reasons why you might be spinning, and how you can avoid it in the future!

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As always, you can find the video's full script below in case you would like to read about certain details.


Check out our other video guides and pro onboard laps here.

Why do kerbs make you spin? (full script)


We've all been there. You see a nice big apex kerb, you want to take all of it, aggressively shorten your line, kind of cut across the corner slightly but the moment you hit that kerb you start oversteering and you might even end up going to a spin.


The question is, why does that keep happening to you? We're going to look at the three key reasons why inside kerbs sometimes cause you to oversteer and most importantly we're going to teach you what you can do in case you take a bit too much kerb and still save the car because of that tip.


Before we dive into some of the physics explanations, let's actually take a look at some kerbs to understand how they differ from the asphalt around them. First of all, they're usually painted. That seems like a really trivial detail but it does affect the grip they give you.


Secondly, and that's the main thing to note, they're really really bumpy and it's something you only start to appreciate if you ever had the chance to really see one in real life. They're absolutely massive and you can see the step-by-step nature makes the car bounce around quite a lot and you can imagine how that costs your car quite a bit of grip.


So now that we understand how kerbs are different and how they can vary between each other, let's look at why they actually cause you to go into a spin. The first reason why taking so much apex kerb usually causes you to oversteer is quite straightforward actually - because of the painted nature of the kerbs as well as the step-by-step bouncy nature, the kerbs just don't have as much grip - meaning that the inside of the car has significantly less grip available than the outside.


What does that mean? The moment you get on the power the rear inside wheel just starts spinning much earlier which means the moment that wheel loses traction the outside wheel actually has a lot of traction so the car starts rotating itself around the centre axis which means you start going into a spin as you hit the throttle.


So that's the first reason - kerbs generally have less grip than the asphalt right next to them. But there's something else about them and quite specific depending on the height of the kerb and that is actually how bumpy they are and how they change the balance of the car as you hit them but also as you get off them.


Now to understand why this is an issue let's look at what happens once you hit a really high apex kerb. This is especially problematic with high sausage kerbs around the apex. The moment the front of the car hits that kerb the front suddenly gets slowed down, whereas the rear doesn't which means the balance suddenly shifts to the front - it's like getting on the brakes just one more time which means you have more weight on the front, the nose of the car wants to dive into the ground and suddenly you have a really unsettled car and combined that with the turning input that you definitely have since we're talking about apex kerbs, that causes your car to oversteer.


A similar sort of problem actually happens at the end once you kind of jump over a kerb. So if you manage to kind of climb on top of the kerb without going into a spin you're facing a second dilemma and that is actually coming off the kerb. So as you can see in some cars, it's quite extreme, the cars kind of fly over the kerb which means once you're in the air - what part actually starts hitting the ground first? It's the front, which means suddenly the front wheels grip again whereas the rear is still in the air and even though in the air that doesn't mean necessarily completely in the air but certainly unload it to an extent that the rear doesn't have anywhere near as much grip as the front.


If you combine that again with steering input, suddenly the fronts start gripping again, the fronts want to pull to a certain direction, whereas the rear doesn't and that just pulls you into a spin as the car just doesn't have any grip on the rear wheels.


And that's the key thing to know. It's not the kerb itself that's causing the problem in isolation, it's the combination of taking a lot of kerb which is causing the car to kind of jump up and down and turning in too much at the same time. And that leads us to the main thing you can do to actually avoid that problem in the first place if you take too much kerb or you want to take more kerb.


You simply gotta straighten your steering a bit but doesn't necessarily mean straightening it up all the way but rather than let's say 90 degrees just going to 45 degrees might just be enough to stabilize the car a bit more in order to go over a bumpy kerb without going into a spin after.


Now that we understand the key factors that drive oversteering around apex kerb taking, as well as what you can do to avoid that problem because the kerbs are so bumpy, there's one final aspect to watch out for and that is the importance of downforce in high downforce cars. High downforce cars such as F1 or LMP cars generate downforce in mainly two ways - a) through the wings on top of the car but also through something called 'ground effect' and that's the key thing to keep in mind.


You have massive diffusers on these cars but the thing is they mainly work if the car is stable. The moment you lift up the car which you do by taking a kerb all that ground effect suddenly vanishes which really kills your downforce. And you can see that in this case, what Porsche did with their LMP1 car the 919 Hybrid Evo, they even added fins to the side of the car to really keep the air flowing in one continuous fashion rather than leaving the car through the sides. So it really shows the importance of why the air needs to flow in a certain way and why mounting a kerb suddenly kills that airflow.


So to wrap up, we talked about the three key reasons why apex kerbs can rotate your car around them and why you start going into a spin. First of all, they simply don't have as much grip, and that's true for any kerb whether it's around the apex or the exit or even the entry of a corner. The moment the side of the car gets onto a kerb that side of the car just doesn't have as much grip available as the other side. End of story.


Second of all, they're really really bumpy so remember the moment you hit a really high kerb, what does that do to the balance? The front suddenly has a lot more grip available the nose wants to dive same once it comes down.


What does that mean? If you struggle with high kerb taking or want to take a sausage kerb and a GT or road car it simply might be enough to open up the steering just a tiny bit just to stabilize the car a bit and let your car fly over the kerb rather than losing grip as you hit the ground again. And lastly, remember if you're in a high downforce car you generally speaking want to take less kerb than a GT or a road car.



#tracktitan #oversteering #spinning #simracing #racingschool