The Skid and How to correct it/ Ross Bentley

Most skids, spins or out of control situations are a result of loss of concentration, driving beyond the limit (too fast), or a simple mistake (which usually upsets the balance and traction of the car). Getting into this kind of trouble is quite easy, especially in adverse weather conditions. And getting out of it can be easy with a little knowledge, some thought and experience.

Skid control is never easy. It is one of the most complex aspects of car control there are. It is in fact a self-contradiction: Skid-Control involves regaining control that has been lost. Knowledge and thought are always good, but during a skid, they are near completely useless. I have seen drivers who have just been practically beaten for a hour with knowledge regarding oversteer, what to do and what not to do: They set out to the SkidCar. It's not their car, there are no obstacles in sight, only open area of endless grippy tarmac, the driving speed is slow, the driver is in a “triggered” state of mind, and with a personal instructor in control besides him.

These people sit in the car, think well about what they are going to do and what they really don't want to do. They set out and...do it. Or at least, they think they did. Recap: They were told to do (a) and not to do (b). They set out, thinking very well on doing (a) and not doing (b), set out, do (b) and think that they did (a). They spend some time argue with the instructors that they did (a), try again, and the same ordeal repeats itself two-three more times. Only after that, does the driver begin to apply corrective input with some efficiency.

Now, let's move fast-forward ten months. The driver has a new car with different handling characteristics, he is driving a wet, bumpy road at dark in a speed of 50mph, alone. The car breaks loose suddenly, would he be able to mimic his still crippled level of performance at the course a year-past?

To teach skid-control to a sufficient level of skill, it would take:

1. Knowing all of the basics of car control – understanding grip, car dynamics, drivetrains and engine layouts, being aware of changes in the coefficient of friction as road conditions vary, knowing how steer, where to look and how, etc. Trying to teach or even simply portray oversteer control in an article – when isolated from these other skills – is foolish at best.

2. Acquiring the aformentioned knowledge not through articles and not via trail and error, and not even in a Skidpan tuition. It takes a special, three-four day-long course for advanced driving and car control, or a dedicated skid-control tuition at the length of seven hours at least! In both cases, the instruction must be professional and based on practice on a special simulator (SkidCar device) and a follow-up drill performed in the driver's personal car, on dry and wet tarmac, and on tight gravel. Skidpan tuitions, where they use low-friction surfaces and inclines to induce the slide, are very ineffective.

Even with (1) and (2) done, the chance for a corrective input in real time to be effective rests between 30-40 precent, and a bad, inaccurate or untimed corrective input will make matters much worst than they would have been if the driver would let the car skid to a stop or brake to a halt.

For the car to suddenly “break away” and the driver recovering from it effectivelly, is none-existant. A driver that really knows how to recover from a skid, will either avoid it or know when it is going to occur, so it's not a surprise. He knows all of the variables that can change the corrective input required: Torque, grip, setup (front to rear grip levels), driveline (rear, front, etc), tranny, cause, existance of electronic controls, skill level and qualifications, speed, even the seat! If a driver reaches a situation where his car suddenly breaks away, he might manage to recover with luck, but he will never manage to perform an accurate, effective solution.

Unfortunately, skid control practice is difficult to come by - you certainly don't want to have to do it in everyday driving! Practice and experience it only in a safe environment.

One of the most common types of skids you may face is when the rear end slides out on you - the oversteer skid. What do you do? FIRST, STAY OFF THE BRAKES! If you touch them you will make matters worse. By braking, you transfer weight forward (the car nose-dives under braking) reducing rear tire traction and most likely causing the car to spin out completely. Instead, JUST LOOK AND STEER WHERE YOU WANT TO GO - this will automatically make you steer in the direction of the skid. In other words, in the direction the rear end is sliding (this is called "opposite lock"). And sometimes, very gently increase the throttle to cause a slight weight transfer to the rear, which increases the rear tire traction. I say sometimes because giving it more throttle may make things even worse. Think about it. What got you into the problem in the first place? Usually, too much speed. The last thing in the world you need now is more speed.

Completely wrong, and for various reasons. First, oversteer is the least common type of skid! ALL cars are set to do the opposite and UNDERSTEER, because oversteer is far too complex for the average road driver! Also, oversteer is not defined as “the rear end sliding on you”. Certain combinations of coarse handling and car setup can result in the car swaying laterally without breaking traction to the rear in particular. This would not be considered as oversteer! Oversteer is defined a rear slip angle larger than the front slip angle.

Second, while it is true that “touching” the brakes “make matters a lot worst”, The average road driver – including one who is a veteren of a single skidpad tuition – will do well by STAMPING on the brakes forcifully and than declutch while straightening the steering. Yes, this will shift weight to the front and off of the rear, but it will also result in two other effects. First, a dramatic lost of speed, and an exponential reduction of the Centripetal force and Angular Momentum that is sliding the car. Also, if the car stops, the skid stops and, if you do hit something, you are likely to just brush it at 8mph instead of crushing into it at 40mph.

Also, braking hard locks up all four wheels, at least momentarily. This makes them slide in the direction in which the moment of inertia is pushing the car. This, along with the reduction of speed, can straighten the car back up.

Furthermore, even when a driver is skilled enough to control oversteer, he should never do it in the prescribed method. It might sound great, but in reality it's much more complicated. Like I have said, there are no magic solutions for a situation like oversteer, and that includes “looking and steering”. What have you basically done by steering like this? Have you removed the cause of the skid? No!

Of course, the cause of the skid cannot be known before the author be kind enough to detail it, but I will tell you of two reasons:

1. In a powerfull rear-wheel drive car (and some four-wheel drive cars), when the driver over-powers the rear wheels with torque by giving it too much throttle.
2. In all drives, by suddenly throwing the car's weight forward by sudden braking or even an aggressive lift off of the throttle, mid corner. Both cases are different and require different inputs. The type of the drivetrain also carries great importance, as well as the existance of electronic software like traction control, the given amout of torque, the amount of grip, the speed, the angle of the skid, etc.

So, you probably understand by now that this is a complicated subject, much more complicated than this article presents it. That's the problem: Presenting a deep and complex subject with extreme simplicity, pretending to teach in writing what can only be taught via an intensive, orginised training program – all without even thinking about the wide audience of drivers (at different levels of skill or understanding of car control), the driving enviornments they deal with, and whether they did understand the article or not (which someone can make sure when he is instructing a student face to-face).

Still, for the sake of disscussion, I want to try and get you to understand the subject better. Of the two different inputs the author stated: The steering and the throttle, it would appear that steering takes priority and throttle is of a lesser importance or perhaps even optional. In reality, it goes the other way around.

If we get oversteer by too much torque applied on the rear wheels, we must reduce the amount of torque applied by...reducing the throttle input. However, usually we should avoid lifting-off completely to avoid a forward weight transfer. Also, with the case of oversteer caused by such a forward weight transfer, we would have to shift the weight forward...by accelerating!

That's what makes oversteer so catchy: Do you have the Huevos Grandes required to accelerate when the car attempts a spin at a high speed (or at least, avoid jerking off of the gas)? For the sake of dissscussion, let's say you did somehow get on the gas, do you have the skill and knowledge to judge the right amount of throttle, plus the nessecary steering correction, in just the right moment?

Remember, the throttle can overpower the driven rear wheels. Even in a front-wheel drive car, the increase of speed might make matters worst (like the author stated), especially when the driver applies too much, too late or does not make any steering correction while operating the throttle. It can also make the front lose grip and get the whole car sliding away from you.

In another article on this subject, referring to the differences between the driveline configuration and it's effect on driving style, Bentley said:

"You often hear people give the advice “accelerate hard in a turn with a front-wheel-drive car to ‘pull’ you out of a skid or slide”. Think about it. If the front tires are at or near their limit of traction, and you accelerate hard, all you are going to do is increase the understeer. Again, the tires have a limit. Respect that limit.” (Ross Bentley, “Different cars, Different techniques?”)

This conclusion of Bentley is right when referring to understeer. However, regarding oversteer, he is plain out wrong! Yes, the front wheels have a limit, so you increase it by taking the steering input out (straightening the wheel) and accelerate with feel. Also, even if the tires do spin somewhat, since the accelerator is usually the weakest car control, you are able to spin the front wheels but still get the weight transferred to the rear. This is GOOD, because the spinning front wheels get pushed away and straighten the car back up.

However, remember, even one hand on the wheel has more control than two feet would have, and two hands on one steering wheel have tenfold the control and authority than one foot (right foot) operating two pedals (throttle and brakes). A throttle correction is complex!

However, a steering-alone correction, as suggested by the author, is much worst. Run the scene at 100mph. How much steering would the driver have to apply and how quickely, to get the car under his control, and how quickely would he have to remove that input to avoid being thrown the other way? Furthermore, there is a difference between “catching” the slide and “recovering” from it. By steering the car, you try to keep the front wheels rolling naturally while making the turning radius wider.

When applied with skill, this can be enough to stop the car from spinning, but not from sliding. The driver will find himself obligated to turn the wheel more and more until he reaches full opposite lock, and than wait for the car to wipe off speed, hoping it would run out of speed before it runs out of road, which sadly tends to occur earlier. Than, the side-swipe would spin the car around only to suffer a second blow from the rail.

Furthermore, turning the wheel reduces overall traction and can make the situation worst by generating drag that shifts more weight to the front, or by reducing the amount of the traction that can be used to accelerate the car and pull it from the oversteer.

I understand from where the author concluded this manner of response to be right. If you drive on good grippy tarmac, at moderate speed, in a weak Rear-Wheel Drive car without a particularly light back-end, power oversteer and oversteer caused by braking in a bend, can be resolved in a sufficient manner by simply letting go of the pedals and steering: “If in doubt, both feet out”. However, take most cars in most conditions, and this correction is less effective, particularly if you dial in normal driver's response times. Even with cars where it might be tolerated, it's dangerous to categorily instruct this manner of recovery because you inherit bad habits that you will later apply in the wrong car/situation.

Once you catch the first slide or skid, be ready for one in the opposite direction caused by over-correcting. If it happens, gently correct for it by looking where you want to go and smoothly try to ease the speed down until you get the car under control again.

As the author described it: Steering where you want to go and than perhaps adding some throttle, what will happen is that the driver will compensate with a certain amount of countersteering, and as he accelerates, the car would suddenly re-grip with the front wheels turned against the corner.

This results in a pendulum effect that makes the moment of inertia toss the whole car ever more violently to the other way, and an increase of speed with the throttle only makes it worst. Besides being physically more severe, the pendulum skid is harder to recover from, because it's sharper and the driver has to remove the steering input and start steering sharply towards the other way in a rush. Also, with the origina slide, the car spins but often stops relatively close to where it started. With the pendulum skid, the whole car (not just the tail this time!) is immediately pointed towards the outside of the corner, leading to a roll-over off of the road or a head-on collision with a car in the opposite lane.

If you experience an understeer skid, with the front end sliding or plowing towards the outside of the turn, the correction is simple. Just ease off the throttle, which transfers more weight onto the front tires giving them more traction, AND STRAIGHTEN THE STEERING OUT SLIGHTLY. Most peoples' first reaction when faced with this type of skid is to turn the steering wheel more and more. But, this increases the problem because the tires were never designed to attack the road at an extreme angle. Tires were meant to face the road with their full profile, not with the sidewall, so their traction limit has actually been decreased. So, decrease the steering input slightly and ease off the throttle gently to allow the front tires to regain their grip, and then begin to steer again.

This paragraph is better but it stands in contradiction to the former. The author says not to “force” the car with the steering when experiencing understeer, so why does he recommend just that during oversteer? It's just the same: You try to “force” the car with the steering, but it does not respond, and you simply keep on putting more and more steering, run out of steering and than it's a question of what you run out of first: The speed or the road...

However, since understeer is recovered from by decelerating, steering more to make the car slide MORE and decelerate more, can sometimes be quite effective. This is why understeer is the preferred situation for the unskilled – it solves itself, and is tolerant to steering-based corrections.

Certain car designs lead to certain handling, and therefore skidding, characteristics. Most cars with a large percentage of the weight over the front wheels (front-wheel-drive cars or rear-wheel-drive cars with heavy engines mounted up front) tend to understeer at the limit. Cars with a large percentage of weight biased towards the rear (mostly mid-and rear-engine cars) tend to oversteer naturally. This is mostly caused by a pendulum effect the weight has on the heavy end of the car. If you quickly try to change direction (as in turning into a corner) in a naturally understeering car, the weight of the front end wants to keep going in a straight line causing the car to plow. In a mid- or rear-engine car, if you lift off the throttle in the middle of a corner (causing weight to transfer off the rear tires, reducing traction and making the car oversteer), the weight of the engine works like a pendulum swinging out and trying to spin the car (“trailing throttle oversteer”).

NO road or race car oversteers naturally. Only few car used in rallycrossing and drifting have natural oversteer and very few rally cars have neutral handling. Otherwise, any car would have some degrees of understeer. Drive it on a plain road of tarmac, maintain a constant speed with throttle and turn the wheel without any Appel Contre-Appel provocation, will it spin? No. So it does not naturally oversteer. Even if you try to turn the wheel more ubruptly, you are likely to aggrevate the understeer or cause the car to “cynical-steer”, it feels like oversteer but it isn't.

As you can see, weight transfer has a great influence on how your car behaves in a skid or slide. Smoothly controlling that weight transfer is the real key to skid control.

If the car begins to oversteer skid and you can't control it as described above, you are going to spin-out. Nothing wrong with that, if you keep your cool, watch where you are going, de-clutch and lock up the brakes - and hopefully don't hit anything. Remember these words, “spin – both feet in”, meaning left foot on the clutch and right foot on the brakes. That is all you can do - besides avoiding the spin in the first place.

Correction: The clutch goes AFTER the brakes, so you have some support with your left foot as you right foot stamps on the brakes. Unless the driver is very skilled, this is the sole manner of performing a sudden stop (no attempt of threshold braking) and the only way to recover from oversteer (no attempt to correct it).

Ross Bentley, Senior Instructor, Driving Unlimited

Professional Race Driver

“But it's Ross Bentley, surely he cannot be wrong?” Well, it's either him or: Chris Harris, Martin Rowe, Tim Harwey, Tiff Needell, Jason Plato, Tommy Makinen, Danny Glatter, O'n Ya'akobson, Lior Levi, Itay Alon, Colin Mc'Rae, and many others. Either they are all wrong, or Ross Bentley is right. I doubt it.