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The Real Truth About Understeer
What exactly is understeer? In purely technical terms, it's a lack of front tire grip. But what does that actually mean? What causes it? How can you get rid of it mid-corner? How can you avoid it altogether? And most importantly, why is it actually MORE dangerous than oversteer?
First, let's understand exactly what understeer means. When you enter a corner and the car begins to "push" toward the outside of the turn, you're experiencing understeer. You've dialed in the correct amount of steering input (turned the wheel the correct amount) but the car is turning less than it should.
REASONS FOR UNDERSTEER
So, why does this happen? This happens because your rear tires have more grip than your front tires. When you begin to turn, instead of the front tires gripping on the road, they slide. This can happen for one of three basic reasons:
1) You've entered a corner too fast (surprisingly, this isn't usually the problem!)
2) You're trying to turn too much (you've actually asked the tires to do more than you need them to do)
3) Your brake and/or throttle inputs haven't loaded the front suspension properly (this is your problem, 95% of the time)
Let's discuss #3 first, as this is the most common cause of understeer. To understand load transfer, also commonly (and incorrectly) referred to as weight transfer, perform this simple exercise:
Place your hand face-down on the table/desk in front of you. Slide it forward on the table. Your hand slides easily because you have very little load forcing it on the table. Now stand up, and lean on your hand. While leaning on your hand, try to slide it forward. It doesn't slide. This is because you have a lot of load on your hand. The same exact thing is constantly happening with your tires. When you have load on your tires, they grip. When you don't, they slide.
Simply put, when you accelerate, load is transfered rearward. When you decelerate, load is transfered forward. Deceleration doesn't necessarily mean braking, as coasting or even easing off the throttle will cause the vehicle to slow down (decelerate). This is even more dramatic when driving up hill, as the slightest decrease in throttle input causes the car to decelerate significantly.
BRAKE RELEASE
So, we know that understeer is caused by a lack of front grip, and we know that we can increase front grip by transferring load to the front of the car. So as long as we decelerate before every corner, we'll never understeer ever again! Right? Well, it's not quite that easy.
The way in which we brake and accelerate, or more importantly, the way in which we release the brakes and roll on the throttle, determines how the load is transfered, how much load is transfered, and most importantly, how much load actually STAYS in the front of the car.
If we brake very hard, a lot of load is sent to the front. However, if we abruptly lift off the brakes and get back on to the throttle, all of that load goes right back to the rear. In fact, when you're accelerating hard, the front tires have so little load that they're barely making contact with the ground. Just think about how well your car would steer if you were doing a wheelie through the turn.
So, how can we accelerate through a corner and still maintain a healthy amount of front load and grip? The answer is proper brake release, followed by sensitive throttle input. Ideally, a passenger should not be able to tell when you've gotten off the brakes and on to the gas.
To do this, you need to revise your braking strategy. Braking "late" or "diving" in to corners and getting on the power early may seem like the fastest way around the track, but this usually slows people down. There is a way to brake late and get on to the throttle sooner, but it can't happen until you've mastered proper brake release.
To start out, brake 10-20% earlier than you normally would. Try to get all of your braking done well before the corner. At this point, you should feel like you broke too early. You have a quarter to half a second of time, which feels like an eternity, in which you don't need to be slowing down anymore, but you don't need to be turning yet. During this "dead space" you focus on one thing, and one thing only: brake release. This is your time to gradually release the brakes and begin to turn in. As you get comfortable with this, you can begin braking where you normally did before, combining this smooth brake release with your turn-in, often referred to as "trail braking." You then need to follow this up with an equally smooth and gradual application of throttle. Smashing on the gas at this point will ruin all of the work you've done up this point with your brake release.
If done correctly, one of two things will happen depending on a variety of factors:
1) The car will be perfectly neutral through the turn and will turn exactly the same amount as you turn the steering wheel.
2) The car will oversteer slightly, turning more than you turn the steering wheel.
No explanation is needed for #1. You're good to go. Congratulations, for the first time ever, your Subaru isn't fighting you through a turn.
OVERSTEER AND "ZERO-STEER"
Next, we have situation #2. This is a GOOD situation to be in, do not be afraid! Clearly, hell has frozen over, as your Subaru is oversteering. How could this have happened? The answer is you've successfully trail braked to the point that you actually have so much front grip that your car is able to turn more than you asked of it. Depending on how quickly you recognize this behavior, you may be able to experience something we call "zero-steer."
As soon as the oversteer initiates, you can roll on the power. If you're quick enough, you'll barely need to correct your steering input (counter-steer) as your throttle input will send load to the rear, reducing front grip. This reduction of front grip stops the oversteer, and you may end up with "zero-steer" where the steering wheel is in the dead center position and the car is turning around the corner almost by itself. At this point, you're simply steering with the gas pedal. More gas steers towards the outside of the turn, less gas steers towards the inside of the turn, and maintaining throttle keeps you on your current path. This is not only the fastest way around the corner, it's also the easiest on your tires. Unfortunately, even for the best of drivers, it's not something you'll experience every corner, but it's sure nice when you do.
Now, assuming you're not quite quick enough and you catch the oversteer a little late, you'll need to make a slight counter-steer correction. This is extremely fast, and extremely minor. We're not drifting, we're not going around the corner with the steering wheel turned in the opposite direction. Simply reduce your steering input (or even temporarily steer in the opposite direction for a split second) and slowly get on to power. Things will quickly sort themselves out and you'll be going around the turn with very neutral handling. Continue rolling on the power, but don't accelerate too much! You'll just end up with understeer again.
As you unwind the wheel and start exiting the corner, you can accelerate more and more. When the wheel is almost straight, you can fully accelerate. It is for this reason that we want to get the car rotated early. The more turning we do at the beginning of the corner, the less we have to do at the end, which means we spend more time on the gas, and less time steering.
I THINK THAT MIGHT BE A BIT BEYOND MY SKILL LEVEL
If this oversteer / zero-steer situation has you scared, or you don't feel that you will be able to recognize the oversteer soon enough, there is absolutely no reason that you ever need to be in this situation. The only way for this to happen is by trail braking too much. This means your brake release continued too far in to the beginning of the corner.
To assure that this doesn't happen to you, simply finish your brake release in a straight line, and start your sensitive application of throttle at turn-in. As you get more and more comfortable, you can try trail braking a little at a time. Do your brake release 1% in to the corner, then 2%, then 5%, etc. Eventually, as you get more confident, you'll find yourself trail braking the first 10% of most corners. Please, PLEASE, keep in mind that "trail braking" is NOT actual braking. This is simply combining your brake release with your turn-in. If you're actually doing any kind of real STOPPING during your turn-in, you are asking for trouble!
THAT'S GREAT AND ALL, BUT I SCREWED UP AND THE CAR IS UNDERSTEERING AS USUAL. NOW WHAT?
When you can't prevent understeer, you can eliminate it mid-corner. Doing so properly is essential, as improperly dealing with understeer is the most dangerous thing you can do, and is responsible for most accidents at the track. "But I thought understeer was safe!?" Well, it's not.
THE MOST COMMON, YET COMPLETELY UNKOWN MISTAKE WITH UNDERSTEER
Before we can talk about eliminating understeer mid-corner, we first need to understand the common mistake that most people make to get them in to really bad situations in the first place. This problem is turning the wheel MORE once the car has started to understeer.
When you think about it, it makes sense. If you want the car to turn more, you turn the wheel more, right? Wrong. What?! If you've asked your tires to turn a certain amount, and they can't, how is asking them to turn even more going to help anything?
An example of this would be in a gym. A man is bench-pressing 200 pounds. He almost has the barbell all the way up, but he's struggling. Then his friend comes over and adds another 20 pounds of weight to his barbell. In this situation, there is no way that the man will be able to lift the 220 pounds, instead, he'll probably drop the weight on top of himself. This is no different with your car, all that will happen is it will understeer more and start to drive completely off the road.
GOT IT. SO NOW WHAT?
So, your car is starting to understeer in a corner. You catch yourself right before you instinctively add more steering. Now instead of having a serious understeer problem, you have options:
1) Reduce your steering input (turn less)
2) Reduce your throttle input (decelerate)
The first option is important to consider. Many times, maintaining your current speed with just a little less steering input is all that is needed to reduce your understeer. If doing so will still allow you to make the corner, you're golden. If it's clear that you're going to drive off the road at your current radius, you move to option #2.
Option #2 has to be dealt with very carefully. As we know, decelerating will send load to the front, increasing front grip. This is a good thing, but too much, too quickly, will cause oversteer. For this reason, you need to be very gradual and sensitive. Lift slowly off the gas. With 10% less throttle will you make the corner? 20%? 30%? Are things really bad? Maybe you need to let off completely, or even brake. That's OK, as long as you do it gradually and smoothly. If you simply lift off the gas and step on the brake you will cause oversteer that is so quick and so violent, you will spin, and exit the track sideways or backwards, guaranteed.
SO UNDERSTEER IS DANGEROUS, AND OVERSTEER ISN'T? THAT SEEMS PRETTY BACKWARDS
Oversteer can be dangerous, but unlike understeer, there are two major kinds of oversteer. There's controllable oversteer, and uncontrollable oversteer. The oversteer you'll experience from trail braking for example, is easily controllable because it's gradual and you're expecting it.
Another kind of equally controllable oversteer is power-on oversteer. This is possibly the easiest kind of oversteer to correct. You got on the gas too hard, too soon, and the rear tires are spinning? Let off. Your problem is gone. The only way to spin out or crash as the result of power-on oversteer is to try to be a drifting, power-sliding, hero that doesn't want to lose a few tenths of a second letting off the gas and regaining traction. As soon as you feel that you've induced that kind of oversteer, lift your right foot and it goes away. That's all there is to it.
SNAP-OVERSTEER
Now, uncontrollable oversteer almost always comes after bad understeer and is commonly referred to as snap-oversteer. This happens when you improperly deal with understeer, and this is usually what people think about when they hear the word "oversteer." It's scary, and it's usually the only kind of oversteer that most drivers experience.
We'll take a typical understeer example. You've failed to properly load your front suspension and/or you're just entering a corner way too fast. The car begins to understeer. Because you haven't read this post, you turn the wheel more to try to make the car turn more. Now you realize that the car is almost certainly going to go off the track and you're running out of road. The outside of the corner is getting closer and closer. You panic and lift off the gas completely and suddenly, maybe even brake. In a split second you go from having excess steering input with no front grip, to excess steering input with an abundance of front grip. What happens? The car turns like you want it to, and then it keeps turning REALLY fast. You try to react by counter-steering, but by this point, it's already too late. In fact, it was already too late when you lifted 2 seconds ago. You're sideways, then you're backwards, and now you're spinning.
What should you do? Well, if you haven't already, you should be hard on the brakes. In fact, as soon as you went more than about 45 degrees sideways you should have been hard on the brakes. But what do most people do? They don't even get on the brakes until they're going backwards, and even then, sometimes they still don't brake. The net result is going off the track sideways or backwards, which can result in rolling the car or hitting a wall. All of which could have been avoided at that very moment you turned the steering wheel more.
That is truth about understeer.
What exactly is understeer? In purely technical terms, it's a lack of front tire grip. But what does that actually mean? What causes it? How can you get rid of it mid-corner? How can you avoid it altogether? And most importantly, why is it actually MORE dangerous than oversteer?
First, let's understand exactly what understeer means. When you enter a corner and the car begins to "push" toward the outside of the turn, you're experiencing understeer. You've dialed in the correct amount of steering input (turned the wheel the correct amount) but the car is turning less than it should.
REASONS FOR UNDERSTEER
So, why does this happen? This happens because your rear tires have more grip than your front tires. When you begin to turn, instead of the front tires gripping on the road, they slide. This can happen for one of three basic reasons:
1) You've entered a corner too fast (surprisingly, this isn't usually the problem!)
2) You're trying to turn too much (you've actually asked the tires to do more than you need them to do)
3) Your brake and/or throttle inputs haven't loaded the front suspension properly (this is your problem, 95% of the time)
Let's discuss #3 first, as this is the most common cause of understeer. To understand load transfer, also commonly (and incorrectly) referred to as weight transfer, perform this simple exercise:
Place your hand face-down on the table/desk in front of you. Slide it forward on the table. Your hand slides easily because you have very little load forcing it on the table. Now stand up, and lean on your hand. While leaning on your hand, try to slide it forward. It doesn't slide. This is because you have a lot of load on your hand. The same exact thing is constantly happening with your tires. When you have load on your tires, they grip. When you don't, they slide.
Simply put, when you accelerate, load is transfered rearward. When you decelerate, load is transfered forward. Deceleration doesn't necessarily mean braking, as coasting or even easing off the throttle will cause the vehicle to slow down (decelerate). This is even more dramatic when driving up hill, as the slightest decrease in throttle input causes the car to decelerate significantly.
BRAKE RELEASE
So, we know that understeer is caused by a lack of front grip, and we know that we can increase front grip by transferring load to the front of the car. So as long as we decelerate before every corner, we'll never understeer ever again! Right? Well, it's not quite that easy.
The way in which we brake and accelerate, or more importantly, the way in which we release the brakes and roll on the throttle, determines how the load is transfered, how much load is transfered, and most importantly, how much load actually STAYS in the front of the car.
If we brake very hard, a lot of load is sent to the front. However, if we abruptly lift off the brakes and get back on to the throttle, all of that load goes right back to the rear. In fact, when you're accelerating hard, the front tires have so little load that they're barely making contact with the ground. Just think about how well your car would steer if you were doing a wheelie through the turn.
So, how can we accelerate through a corner and still maintain a healthy amount of front load and grip? The answer is proper brake release, followed by sensitive throttle input. Ideally, a passenger should not be able to tell when you've gotten off the brakes and on to the gas.
To do this, you need to revise your braking strategy. Braking "late" or "diving" in to corners and getting on the power early may seem like the fastest way around the track, but this usually slows people down. There is a way to brake late and get on to the throttle sooner, but it can't happen until you've mastered proper brake release.
To start out, brake 10-20% earlier than you normally would. Try to get all of your braking done well before the corner. At this point, you should feel like you broke too early. You have a quarter to half a second of time, which feels like an eternity, in which you don't need to be slowing down anymore, but you don't need to be turning yet. During this "dead space" you focus on one thing, and one thing only: brake release. This is your time to gradually release the brakes and begin to turn in. As you get comfortable with this, you can begin braking where you normally did before, combining this smooth brake release with your turn-in, often referred to as "trail braking." You then need to follow this up with an equally smooth and gradual application of throttle. Smashing on the gas at this point will ruin all of the work you've done up this point with your brake release.
If done correctly, one of two things will happen depending on a variety of factors:
1) The car will be perfectly neutral through the turn and will turn exactly the same amount as you turn the steering wheel.
2) The car will oversteer slightly, turning more than you turn the steering wheel.
No explanation is needed for #1. You're good to go. Congratulations, for the first time ever, your Subaru isn't fighting you through a turn.
OVERSTEER AND "ZERO-STEER"
Next, we have situation #2. This is a GOOD situation to be in, do not be afraid! Clearly, hell has frozen over, as your Subaru is oversteering. How could this have happened? The answer is you've successfully trail braked to the point that you actually have so much front grip that your car is able to turn more than you asked of it. Depending on how quickly you recognize this behavior, you may be able to experience something we call "zero-steer."
As soon as the oversteer initiates, you can roll on the power. If you're quick enough, you'll barely need to correct your steering input (counter-steer) as your throttle input will send load to the rear, reducing front grip. This reduction of front grip stops the oversteer, and you may end up with "zero-steer" where the steering wheel is in the dead center position and the car is turning around the corner almost by itself. At this point, you're simply steering with the gas pedal. More gas steers towards the outside of the turn, less gas steers towards the inside of the turn, and maintaining throttle keeps you on your current path. This is not only the fastest way around the corner, it's also the easiest on your tires. Unfortunately, even for the best of drivers, it's not something you'll experience every corner, but it's sure nice when you do.
Now, assuming you're not quite quick enough and you catch the oversteer a little late, you'll need to make a slight counter-steer correction. This is extremely fast, and extremely minor. We're not drifting, we're not going around the corner with the steering wheel turned in the opposite direction. Simply reduce your steering input (or even temporarily steer in the opposite direction for a split second) and slowly get on to power. Things will quickly sort themselves out and you'll be going around the turn with very neutral handling. Continue rolling on the power, but don't accelerate too much! You'll just end up with understeer again.
As you unwind the wheel and start exiting the corner, you can accelerate more and more. When the wheel is almost straight, you can fully accelerate. It is for this reason that we want to get the car rotated early. The more turning we do at the beginning of the corner, the less we have to do at the end, which means we spend more time on the gas, and less time steering.
I THINK THAT MIGHT BE A BIT BEYOND MY SKILL LEVEL
If this oversteer / zero-steer situation has you scared, or you don't feel that you will be able to recognize the oversteer soon enough, there is absolutely no reason that you ever need to be in this situation. The only way for this to happen is by trail braking too much. This means your brake release continued too far in to the beginning of the corner.
To assure that this doesn't happen to you, simply finish your brake release in a straight line, and start your sensitive application of throttle at turn-in. As you get more and more comfortable, you can try trail braking a little at a time. Do your brake release 1% in to the corner, then 2%, then 5%, etc. Eventually, as you get more confident, you'll find yourself trail braking the first 10% of most corners. Please, PLEASE, keep in mind that "trail braking" is NOT actual braking. This is simply combining your brake release with your turn-in. If you're actually doing any kind of real STOPPING during your turn-in, you are asking for trouble!
THAT'S GREAT AND ALL, BUT I SCREWED UP AND THE CAR IS UNDERSTEERING AS USUAL. NOW WHAT?
When you can't prevent understeer, you can eliminate it mid-corner. Doing so properly is essential, as improperly dealing with understeer is the most dangerous thing you can do, and is responsible for most accidents at the track. "But I thought understeer was safe!?" Well, it's not.
THE MOST COMMON, YET COMPLETELY UNKOWN MISTAKE WITH UNDERSTEER
Before we can talk about eliminating understeer mid-corner, we first need to understand the common mistake that most people make to get them in to really bad situations in the first place. This problem is turning the wheel MORE once the car has started to understeer.
When you think about it, it makes sense. If you want the car to turn more, you turn the wheel more, right? Wrong. What?! If you've asked your tires to turn a certain amount, and they can't, how is asking them to turn even more going to help anything?
An example of this would be in a gym. A man is bench-pressing 200 pounds. He almost has the barbell all the way up, but he's struggling. Then his friend comes over and adds another 20 pounds of weight to his barbell. In this situation, there is no way that the man will be able to lift the 220 pounds, instead, he'll probably drop the weight on top of himself. This is no different with your car, all that will happen is it will understeer more and start to drive completely off the road.
GOT IT. SO NOW WHAT?
So, your car is starting to understeer in a corner. You catch yourself right before you instinctively add more steering. Now instead of having a serious understeer problem, you have options:
1) Reduce your steering input (turn less)
2) Reduce your throttle input (decelerate)
The first option is important to consider. Many times, maintaining your current speed with just a little less steering input is all that is needed to reduce your understeer. If doing so will still allow you to make the corner, you're golden. If it's clear that you're going to drive off the road at your current radius, you move to option #2.
Option #2 has to be dealt with very carefully. As we know, decelerating will send load to the front, increasing front grip. This is a good thing, but too much, too quickly, will cause oversteer. For this reason, you need to be very gradual and sensitive. Lift slowly off the gas. With 10% less throttle will you make the corner? 20%? 30%? Are things really bad? Maybe you need to let off completely, or even brake. That's OK, as long as you do it gradually and smoothly. If you simply lift off the gas and step on the brake you will cause oversteer that is so quick and so violent, you will spin, and exit the track sideways or backwards, guaranteed.
SO UNDERSTEER IS DANGEROUS, AND OVERSTEER ISN'T? THAT SEEMS PRETTY BACKWARDS
Oversteer can be dangerous, but unlike understeer, there are two major kinds of oversteer. There's controllable oversteer, and uncontrollable oversteer. The oversteer you'll experience from trail braking for example, is easily controllable because it's gradual and you're expecting it.
Another kind of equally controllable oversteer is power-on oversteer. This is possibly the easiest kind of oversteer to correct. You got on the gas too hard, too soon, and the rear tires are spinning? Let off. Your problem is gone. The only way to spin out or crash as the result of power-on oversteer is to try to be a drifting, power-sliding, hero that doesn't want to lose a few tenths of a second letting off the gas and regaining traction. As soon as you feel that you've induced that kind of oversteer, lift your right foot and it goes away. That's all there is to it.
SNAP-OVERSTEER
Now, uncontrollable oversteer almost always comes after bad understeer and is commonly referred to as snap-oversteer. This happens when you improperly deal with understeer, and this is usually what people think about when they hear the word "oversteer." It's scary, and it's usually the only kind of oversteer that most drivers experience.
We'll take a typical understeer example. You've failed to properly load your front suspension and/or you're just entering a corner way too fast. The car begins to understeer. Because you haven't read this post, you turn the wheel more to try to make the car turn more. Now you realize that the car is almost certainly going to go off the track and you're running out of road. The outside of the corner is getting closer and closer. You panic and lift off the gas completely and suddenly, maybe even brake. In a split second you go from having excess steering input with no front grip, to excess steering input with an abundance of front grip. What happens? The car turns like you want it to, and then it keeps turning REALLY fast. You try to react by counter-steering, but by this point, it's already too late. In fact, it was already too late when you lifted 2 seconds ago. You're sideways, then you're backwards, and now you're spinning.
What should you do? Well, if you haven't already, you should be hard on the brakes. In fact, as soon as you went more than about 45 degrees sideways you should have been hard on the brakes. But what do most people do? They don't even get on the brakes until they're going backwards, and even then, sometimes they still don't brake. The net result is going off the track sideways or backwards, which can result in rolling the car or hitting a wall. All of which could have been avoided at that very moment you turned the steering wheel more.
That is truth about understeer.
