LESSON 2: Understeer and Oversteer
Enabling Learning Objectives
1. Define Understeer. Give an example of when understeer may occur.
2. Define Oversteer. Give an example of when oversteer may occur.
3. Explain what a tire’s “Foot Print” is.
4. Define Counter steer.
5. List and describe two (2) ways to prevent oversteer.
6. List and describe two (2) ways to prevent understeer.
7. List and describe two (2) ways to correct oversteer once it has occurred.
8. List and describe two (2) ways to correct understeer once it has occurred.
9. List and describe three (3) different types of differentials.
Terminal Learning Objectives
Create a journal or log book. Take your vehicle to a safe location or track and bring your car to the limit at which you experience oversteer and understeer individually. Write down your experiences and details of how each is experienced. Such things that can be noted are speeds traveled, degree or difficulty of turn taken, whether it was oversteer of understeer, how much input was given, whether the throttle was depressed or left alone, etc. Compare notes with other students to see their findings.
1. Understeering: what it is, how it happens and how you can stop it.
Understeer is when your vehicle turns less than the steering input given. Have you ever been playing a video game, such as Gran Turismo 3, and had a few situations where it seemed no matter how hard you turned the wheel the car just didn’t want to follow the front wheels? That’s understeer, this situation is caused by a number of factors. Understeer, especially in FRs, is considered a lack of skill because of the type of situations that have to present themselves in order for understeer to occur. The following will describe the situations in which you may experience understeer.
Loss of front tire traction:
If your front tires are weak, hot, cold or badly worn, you will, most likely, experience understeer. This is because the amount of traction, or force enacted through friction that causes items in motion to stop, that is dedicated towards guiding the front end of the car in the designated direction is deteriorated by a great amount. This creates a situation in which the front tires cannot find the grip needed to pull the car around so the cars forward momentum is continued and the car will actually slide over the front tires partially, if not completely, nullifying the steering of the front tires.
Front wheel lock (skidding):
Much the same as the above mentioned item, the traction on the front tires is lost so greatly that the front tires cannot do any steering. In addition to this, the front tires are ceased. This causes steering failure because the front tires, must stay in constant rotation in order for them to correctly guide the car in the direction they they are pointing. When the front tires are locked, the cars forward momentum is continued and the car will continue in a straight line no matter which way the tires are facing or how much they are turned.
The front wheels are doing all or part of the driving:
As far as this lesson is concerned there is no real concern with this, but it is good to know for reference purposes. In order to grasp this concept, you have to understand that tires are only capable of doing 100 percent of any one thing at a time. When you have power going to the front wheels (in the instance of a FF) 100 percent of the power is going towards driving the car forward. You can see that this leaves no room for the front tires to do any guiding. This is why you will always hear about FFs constantly battling with understeer through turns. Under hard driving, a front wheel drive will experience a condition called “Complete Understeer” in which the car literally cannot turn at all. This is due to the fact that the person who is driving the car is trying to “overdrive” the abilities of the front tires. The only way to combat this type of understeer is to brake or lift your foot off of the accelerator throughout the turn.
2. How do you stop understeer from occurring.
There are a few ways in which FR cars can prevent understeer from occurring. Since FR cars aren’t very prone to this condition the prevention measures aren’t very plentiful so it’s up to the individual driver to posses the skill to stop understeer before it happens.
That’s right! The number one way to prevent understeer from happening is practice and plenty of wheel time. Understeering in an FR is usually chalked up to a lack of skill and/or experience with the vehicle operator due to the fact that understeer isn’t a condition in which FR cars are very prone to. So the way that most instructors will tell you to help prevent understeer is to simply get out on the track and practice.
Make sure front tire condition is adequate for the type of driving you will be performing:
Simply put, make sure your tires are right for the conditions. If you know you will be driving harder than usual (e.g. track driving) then make sure that your tire pressure and tread wear are substantial. Likewise, if you know that you will just be driving in idea conditions in traffic or city driving, then your tires won’t necessarily have to be in as good of a condition as if you were on the track.
Learn Proper Braking Techniques:
ABS, or Anti-Lock Braking System, is a huge crutch that modern drivers have come to depend on. They can literally step on the brakes as hard as they please and they will almost never experience wheel lock. This is something that most drifters don’t have the luxury of and even if you do, you should still learn threshold braking because the old saying stands true, “A good driver without ABS will stop and corner better than a poor driver with ABS.” To this day, nothing that technology can produce can substitute for the proper use of your right foot. How you brake is very important to controlling your car through a turn. If you learn proper threshold braking techniques then you will find that your car will almost never experience understeer under braking.
***NOTE: Threshold braking will be covered in lesson 4 of this section.***
3. What to do one understeer occurs.
Once understeer has happened a good question comes to mind, and this is what even the most experienced drivers can forget, what to do next. The following steps, if followed carefully can be very useful in aiding in the correction of understeer. Remember, I can only guide you in the prevention and correction of understeer, the rest is totally up to you and your willingness to practice.
DO NOT PANIC:
This is the first and most important and crucial step in correcting understeer. Panic is the number one killer of cars and drivers alike. It is very important that you understand that understeer is not life threatening if corrected tactfully, if you panic the chance of you being able to correct understeer in time is greatly reduced.
Slow down, but do not lock your front wheels:
If possible, try to avoid using the front brakes. If your car is understeering, using the brakes may only make the situation worse. Release the gas and brake, if you drive a manual transmission car, depress the clutch to relieve the drive off of the rear wheels even further. This should help to propel the car in the right direction.
Do not try to correct this with further steering input:
If your wheels are not locked completely in the turn, then you will want to continue turning in an attempt to alleviate understeer. If your wheels are, in fact, already locked completely to the left or right or further steering input does not assist, then DO NOT attempt to steer in the other direction, this will only worsen the understeering condition and, in most cases, create an out of control spin that could place you and your car in further danger. Keep steady application of the steering wheel input and rely on other factors to correct this.
If you have time to use the brakes, do so gradually and slowly:
If you are understeering but you sense that you have enough time to react with the brakes then apply the brakes SLOWLY and GRADUALLY until the front end begins to steer in the guided direction. This is to ONLY be used if the cause of the understeer is too much speed for the front tires to compensate for. If your cause is simply a loss of traction on the front wheels or front wheel lock, do NOT use this technique.
Release the front brakes:
This technique is to ONLY be used if the cause of you understeering is a forward skid. If your front tires are locked, your car cannot turn, what you will want to do is to deliberately, not quickly, release the brakes. In other words, do not snatch your foot off of the brake pedal, rather, steadily remove your foot off of the brake pedal until the car returns to the guided direction.
Use the emergency brake:
WARNING! This is a highly advanced technique and should only be used by highly experienced and trained drivers. This technique, if used in correctly will only worsen your situation by either contributing to the understeer or sending your car into and out of control skid. If you feel that you are ready to try this maneuver practice it in a large open area first before having to rely on it in time of emergency. What you will want to do is induce understeer (by any means) then while your car is skidding forward, quickly and abruptly yank the E-brake up. This will lock your rear wheels and cause the rear end to shoot around in the guided direction of the front wheels. Once again, this technique requires a lot of skill to pull off properly and should not be used by amateurs. If you pull the E-brake to slowly, the rear tires will simply slow down causing your car to understeer more and if you aren’t ready for the sudden jolt caused by the car whipping around then you will spin out of control rending you out of control and placing your car in more danger than it was when you were understeering.
If you’ve ever spun out while making a turn, had to correct or straighten a car out after or in the middle of a turn, then chances are you’ve experienced oversteer. Oversteer is the opposite of understeer, in which your car will turn MORE than the given steering input. The fact that you are most likely driving a rear wheel drive car puts you in a high susceptibility for this to occur. Also, unlike understeer, oversteer isn’t usually looked at as being the drivers fault. Unless the driver has blatantly oversteered the car by error, this can usually be looked upon as a slight error in judgment or a fault in the track’s texture or conditions of the tires.
A popular argument amongst instructors is the gravity of this condition. While all will admit that this condition is in fact dangerous, a lot will argue that it is no where near as dangerous as understeer especially when concerning drifting. This is due to the fact that oversteer is easier to correct and prevent than understeer, where as understeer is something that an inexperienced driver will most likely not expect, oversteer is something that is more forcefully triggered. Some conditions in which understeer occur are as follows:
Too much steering input for the turn:
This is part of the operator error factor that is associated with oversteer. If you are taking a mild to moderate degree turn and you give full steering input, chances are your car will “over turn” the angle of the turn. This is common amongst beginner to intermediate drivers. However, it is NOT uncommon for an advanced driver to experience this as well.
Loss of traction at the rear wheels:
As implied, this is the exact opposite of the equivalent condition when understeering. Instead of not enough grip in the front, you have “too much” grip in the front and not enough in the back. This will cause your front end to swing the rear end of the car around. This condition often results in a spin out.
Wheel lock at the rear wheels:
Like front wheel lock, rear wheel lock is dangerous. This occurs when a person attempts to turn and applies full pressure to a non-ABS driven system or when a person applies the emergency brake during a turn. This condition, like the above mentioned condition, will most often result in a spin out.
Too much power given to the rear wheels during a spin (fish tailing):
If you were to approach a turn at a lower speed and then abruptly accelerate, your rear end would noticeably swing out causing the operator to have to take corrective measures to straighten the car out. This occurs because the rear tires have 100 percent of their function dedicated to accelerating the vehicle so griping throughout a turn is not something they are able to do. When this occurs an audible squeal will most likely be heard coming from the rear of the car as the rear tires begin to lose traction and literally spin over the ground as the vehicle is turning, this has the same, but more controllable, effect as rear tire traction loss.
An “UNLOADING” of the rear wheels:
As it implies, this is when you “unload” all of the driving stress off of the rear wheels. This causes the weight to transfer forward reducing rear traction and consequently causing the rear end to swing around. An example of this would be to make a moderate speed turn and the push the clutch in and rapidly “pop” the clutch out. This will cause the stress to rapidly unload and load to the rear wheels. This techniques is known as clutch kick and will be covered in later lessons.
5. Ways to prevent oversteer.
There are several ways to prevent oversteer. As with oversteer they are mostly concerned with the operator, but they can also be prevented through measures taken during and before driving.
As with understeer, you can prevent oversteer by getting in the driver’s seat and getting some wheel time. All instructors will agree that practice is the only way to get a feel for your car’s rhythm and balance and to take advantage of that during drifting.
Maintain and always check your tires:
Tire pressure and tread wear are HUGE deciding factors in oversteer. Higher tire pressure in the rear will cause the “footprint”, or portion of your tire that makes contact with the ground”, to reduce causing rear traction to suffer. Also, if tread wear is heavily apparent this will cause grip to suffer and while it may not bother you when drifting you will notice that every day driving will be extremely demanding and require large amounts of concentration, this will also account for early driver fatigue.
Practice proper braking techniques:
Once again, as with understeer, oversteer can be prevented by properly braking and never “over braking” your turn. You do not want to slow down to a speed that is unnecessarily slow for your turn you are attempting to make. This will cause most, even the most experienced, drivers to compensate by accelerating and this will cause a power oversteer.
Proper throttle control:
As mentioned above, if you accelerate heavily into a turn this will cause your rear end to break traction and cause oversteer. If you practice proper throttle control throughout turning you will notice that you can control your turns and actually take them faster then if you were accelerating fully.
6. How do you correct oversteer once it’s occurred?
There are a several ways in which you can correct oversteer if you are experiencing it. These, like understeer, require concentration and precise judgment. If applied correctly, you will be able to get out of most, not all, oversteering situations, and you should be able to have a good understanding of what your car wants to do when you experience these and attempt to correct the situation. Remember unlike understeer, oversteering situations almost ALWAYS require corrective steering input.
Relax and try not to panic:
Believe it or not, even though oversteer is considered not as dangerous or as scary as understeer, drivers, especially inexperienced or beginning drivers, tend to tense up more when oversteering because the thought of spinning is scarier to most people than sliding in a straight line is. You have to try to remain calm and depend on your training to kick in when you need it most. Panicking will only cause you to hesitate or take corrective measures to hastily which will only put you in a more grave situation.
Gradually release the throttle:
If you have experienced oversteer because of heavy acceleration, then you will want to gradually but deliberately release the throttle until the car begins to correct. Simply put, do not snatch your foot off of the gas pedal, take it easy and reduce gas pressure until the car begins to go where you put it. Remember as with all oversteering situations, corrective measures call for corrective steering input.
Try to reduce traction in the front wheels:
This is a more advanced technique, but can be mastered in a few hours of continuous practice. What you will want to do is when you begin to oversteer, take your front wheels just passed the threshold of lock. This will cause your front tires to lock and unlock rapidly but should induce enough corrective understeer to give you time and ability to correct your car’s oversteer.
Counter steering is the act of steering against the direction of the car’s rear end movement. For instance, if you turn left and your rear end starts to swing around to the left, you will steer right in order to counter the turn, hence the term “counter”. Counter steer is highly important in drifting and even though it is naturally applied by all drifters it is rarely done correctly by novice to intermediate drifters. Counter steering is the most basic and effective way to correct oversteer. There is a method of counter steering used in drifting called “Tracing” in which you only give the amount of corrective input required to keep your car sideways, this will be covered in later lessons.
Very briefly, a good way that drivers, from the most novice to the most experienced, will try to combat over and under steer is through the use of differing types of differentials. A differential is a unit used in your car’s drivetrain that delivers and distributes power to the driving wheels of your vehicle. The way it distributes power is determined by its design and how it is set to engage. The basic types of differentials are as follows:
Open Differential (a.k.a The Stock Diff.)
An open differential operates through a set of three spider gears. One is placed on the bottom and one is placed on either side of the differential housing. The main gear (bottom) is driven by the driveshaft and will apply power to the individual spider gears depending on which wheel has LESS traction. This is apparent in most cars that come from manufactures today. Due to the fact that in a turn the outside wheel wants to spin faster through the inside wheel, this differential was made to assist that. This creates a greater feeling of control when daily driving and in some cases when driving on the track. You can experience an open differential by having a friend accelerate rapidly and watch to see as only one tire (the power wheel) will leave down a track on the ground. This differential isn’t very good for drifting as there is always one tire with constant traction, but it is still very possible to drift with this differential although most will recommend that you get the following differential.
Limited Slip Differential (L.S.D The Drifters Drug)
LSDs are very popular amongst drifters. This type of differential uses clutch-type gearing, as opposed to spider, to deliver equal power to the wheels while accelerating. Due to current technology, almost all LSDs will still be able to differentiate the inside and outside wheels during normal day to day driving, which is why most drivers will chose this differential. There are 4 basic types of LSD: the 1 way in which the control is noticeable under acceleration only, the 1.5 way in which control is noticed under acceleration and throttle off, the 2 way in which acceleration and braking both are given locking points, finally the adjustable in which you can, either manually or electronically, adjust the points in which your LSD engages to lock both wheels in the same rotation.
This is tailored for the more serious drifter who has a separate car for drifting and driving. This differential literally locks the two wheels together so that they will always rotate at the same speed regardless of what the action is. There is still the ability for the inside and outside wheels to differentiate but it takes a lot more for the wheels to do this and if you accelerate in anyway while turning both wheels will quickly meet the same speed. This, once again, is intended for the drifter who has a car for DRIFTING ONLY and one for driving home. This differential utilizes a single clutch and gear to actuate between differentiating and locking.
The Solid Differential
This differential really isn’t even intended for drifting but can be used. As the name implies this is a solid gear that links both wheels at the same speed. There is no differentiating action at all between the inside and outside wheels. This is NOT intended for daily driving and will make a normal car EXTREMELY difficult to drive. This differential was made for drag racing so that power is always distributed evenly and so that draggers will not have to worry about any “excess” moving parts in the rear end.
Differentials are very useful when driving or drifting and provide for amazing amounts of control over your vehicle when used correctly. Take some time and do some research to find out which differential is right for you.