OversteerFrom TrackpediaOversteer, skidding or "loose" is the tendency of some cars to lose grip and skid away from corners with the rear axle. At the beginning of this procedure, the front of the car seems to turn too much too quickly, hence the name "oversteer". For the unskilled, there's one way out of oversteer and one way only: Full-force braking!
Causes of oversteerAs discovered in the Undesteer article, oversteer is not the basic handling characteristic of any car. Furthermore, a car that turns by tilting it's front wheels into the corner (as all cars do) will never experience oversteer untill afer turning the wheel into the corner. This fact alone can help drivers anticipate when oversteer is likely to occur. Oversteer is caused by one of two causes. The first of which is an agressive shift of weight to the front of the car. If you brake around the corner or even drive through it off-throttle, you are likely to experience oversteer at the limit, after you finished turning the wheel into the corner. In fact, the oversteer would be strongest if you jerk off of the gas or stab the brakes just after you finished turning the wheel into the corner. This will cause the car to oversteer extremlly sharply, unless you brake hard enough to overload the front wheels, which will rather cause understeer again. This kind of oversteer is likely to be caused by a bad attempt at recovering from understeer: The driver will steer more and more sharply into the corner and, eventually will panic and sharply close the throttle or brake, which will than make the car react the sharp steering input suddenly and tighten the line and cause sudden oversteer. Another cause of oversteer is sharp acceleration. If you drive a powerfull rear-wheel driven car (and some all-wheel drive cars), especially on slippery surfaces, and you accelerate suddenly at the apex of the turn (after turning the front into the corner) you will shift weight to the rear wheels, giving them more grip, but you will also 'preoccupy' them with acceleration so much that they would not be able to accelerate and turn simultanously, so the rear will kick around. Other causes of oversteer are when the car passes on a slippery patch of road. First, it's front wheels touch the oil or ice and slide into an understeer but the understeer quickly resolves itself when the front touch the grippy pavement again. By now, the rear will be placed on the slippery patch and start to oversteer. This is an extremlly hard kind of oversteer to recover. It happens suddenly, with little feedback or readiness of the driver. Likewise, a downhill incline could cause oversteer (generating a weight shift to the front), as could a bump or crest on the road (causing the most agressive kind of slide). The last possible cause of oversteer is a strict provocative action of the driver: Either suddenly pulling the handbrake after turning the wheel, shifting to a low gear, kicking the clutch while applying throttle (in a strong rear-wheel drive) or turning from side to side. You turn the wheel right, and the center of gravity moves right and understeer is experienced. If you now turn back to the left in just the right moment, you will create a pendulum effect that would multiply the forces working on the car. The center of gravity will suddenly shift from side to side (rather than from side to center) and the car would slide. Scenario 1: In this video, instructor Itay intentionally oversteered the car with the brakes and countersteered (note the application of the correct steering technique!) while keeping neutral throttle. By keeping the power neutral, the rear re-gripped, but the front did not loose traction and was able to steer the car back on the right track. By correcting eariler, one could avoid countersteering, and therefore apply more power to actually accelerate out of the oversteer. Oversteer recoveryThe basic technique often thought to counter oversteer includes an operation called "countersteering". Originally, this refers to a biking manouver. Another name is "Opposite Lock", which in turn first refered to a rallying technique that involved creating oversteer by an early and ubrupt turn-in, and sustain the slide towards the corner with sharp countersteering, effectively turning the wheel from the edge of the rack to the other edge (from lock to lock). We will use both terms loose during disscussion, but opposite lock usually refers to sharp countersteering. The idea of countersteering is to keep the front wheels pointing the car towards the intended direction, and thus balancing out the rear and front axles of the car by matching the angle of the front wheels to the slip angles of the rear wheels and making the radius larger. This might manage to "balance" the slide at slower speeds, but not to recover from it. Meaning, if applied quickly and correctly, opposite lock might stop the back-end from attempting a spin, but the car will keep on driving sideways untill it starts to run out of speed, which often does not happen before you run out of road. However, persuming that the slide did end, the lock is being put through again and the car keeps on driving and to avoid sliding the other way. This technique is fine at a very basic level, but is not always the appropriate technique. One particularly irrelevant technique is to "steer into the skid and power-out" or "opposite lock & throttle", which is a good recipe for flying across the other way far more agressively. The rule "if in doubt, both feet out" might work in slower speeds, but is also usually incorrect. In a slightly more advanced level, oversteer has different methods to deal with according to the event. However, as said, other factors are in work too. Therefore, a whole veriaty of suggested solutions can be made. However, before we even begin to disscuss the technical recovery, we need to know how and when to apply it. The problem with oversteer it that it is less expected, more misleading, and therefore, any countermeasures are taken, if at all, at a generally late stage of the skid. However, there is a method of sensing the skid beforehand, like with understeer. While the latter is being felt through the steering wheel, oversteer is felt through the back of the seat. It's therefore imperative that the driver be positioned correctly in the car, and seating upright, with his back and bottom tight into the back of the seat. This can be maintained by operating the clutch before turning into corners, and than leaning the left foot against the footrest and squizzing it. Scenario 2: Former rally-driver Lionel Firm drives a car on a skidpan simulating grip levels of ice. When the car understeers, lifting off of the power generates oversteer but due to a quick reaction, Firm gets on the gas before the car sways from the intended direction, thus removing the need to countersteer and because of that, he can actually acclerate (and not just keep a constant speed) and power out of the slide, because he does not need the front wheels to redirect the car back on the right line, as it still is on that line. Less steering -- more power. Firm also talks about an intersting method of prolonging the slide: Accelerate somewhat with the wheel still turned inside. In given conditions, the increase of speed keeps the slide going.  
Scenario 3: Tomi Makinen explains how to make an emergency recovery from sharp oversteer in a WRC car. Once the rear starts to slide, the center-differential transsmits power to the front to pull it back straight. Thus, by applying a lot of power, the driver gets the front tires to spin and push back into the right line. Because the front wheels are already spinning, one needs to keep the wheel straight or countersteer just slightly. Usually, you do not want to countersteer if the wheels are spinning. Scenario 4: In this case, Jason Plato was snapped completly sideways and had to correct as hard as possible to redirect the car. By getting hard on the gas, he got the front wheels to spin back towards the right direction and also to shift weight backwards. With the addition of full opposite lock, it straightened him out very nicely. However, if the speeds involved were higher, the engine might lack the ability to spin the front wheels, in which case it would be better to keep constant throttle rather than accelerate. As Tim Harvi mentions, this is impossible in a RWD, as the rear wheels would spin rather than the front. The only case where a correction without throttle is acceptable, is if power oversteer occurs in a modest uphill/off-camber slope, it might be appropriate to gently let go of the throttle and blip it if nessecary. Beware of the tankslapper, though. Therefore, both inducing and controlling oversteer is a balance of steering and throttle inputs, and should be done at the nenosecond when you feel the back sliding: Front-wheel driven carsThe solution for a front wheel driven car is to reduce the steering angle or straighten the steering, while picking up the throttle slightly to pull the car forward and back straight. Some trainers say that if the angle of the oversteer is such that requires to turn the wheel against the corner, it's likely that you made the input too late or that you did not use enough throttle. This is not entirely true. Some situations of oversteer are likely to require some countersteering, but even than the steering angle required is quite shallow, so I usually say that "there is no opposite-lock in a front-wheel drive." In fact, even if it does seem you need to countersteer, it might not be necessary. How? If the car is powerfull enough, it might be possible (in the slower corners and on slippery surfaces) to accelerate just enough to spin the front wheels slightly; just enough to still get some acceleration going and allow the rear to grip again, but also to spin them wheels, which will cause them to push back into line, with the steering still pointed straight or near-straight. If you have to countersteer, reduce the throttle input to constant throttle, so the car is rolling sideways at a constant speed. Accelerating or decelerating when sideways with the wheel turned against the corner - is likely to end badly, or at least reduce the efficiency of the recovery. If you are off-throttle, the rear will keep on coming around. You might manage to "catch" it with the steering, but if you don't manage to bring it back to straight, what difference does it make? You will find yourself sliding sideways on full opposite lock. Any attempt to brake or too apply the throttle input at this stage will kick the car in the opposite direction, so you just have to wait in hope that it would lose momentum before it runs out of road, which is unlikely, especially when going downhill. Rear or All-Wheel DriveIn cars that are rear or all-wheel driven, you cannot harness the throttle as much to your rescue. In fast corners, if you react quickly enough to a slide, you might not have to countersteer, just pick up the throttle with enough feel to get the car pitched around the corner. However, in most situations, it's likely that a certain countsteering be required.
Scenario 5: Chris Harris is intentionally creating the slide and, out of an attemp to pursue greater angles and longer slides, he puts the steering correction before the throttle application. This is not like the (bad) technique of countersteering and accelerating, because than the rear grips with the front tires pointed against the slide, throwing the car the other way. Additionally, it makes the slide longer and possibly causing you to overshoot and miss the point of no return. Here the wheel is straightened before the power is being applied. Particularly mark his words: "The cars often get to big angles but the front wheels are always dead straight". There's normally no countersteering involved in correcting FWD oversteer. It would normally indicate a bad/late/exaggerated correction. In each case, looking where you want to go is really important and will determine your success. If you haven't done so from the beginning, you will need to shake your head away from the wall you will probably be facing, and focus on a visual target in the direction of intended travel. Once the technical skill is mastered, looking where you want to go is what will determine the success of the procedure in real-time. Here is an example: Just work percisely with the throttle while looking and steering in the right direction. If you just let your eyes steer, you get one of the following: (a) Under-reaction: The front will stop the spin or "catch" the slide, but will not stop it, so the driver would have to keep steering untill he runs out of lock and hope for the car to lose speed and regrip, before it runs out of road. IIn given conditions this can be misinterprated as a clean recovery. (b) Over-reaction: a stronger, faster and more dangerous slide the other way. (c) No reaction: The car spins and the spin can even be aggrevated by the steering correction.  If we refer to the car as a whole as a body capable of sustaining a certain amount of energy, and as we steer into the corner and get oversteer, should we simply turn the wheel the other way, we will only increase the amount of force acting on the car. Similarly, if we add power without correcting with the steering, our chance of recovery is also decreased. If we first correct with the steering and than add throttle, we end up giving the car too much of both applications.
Another extremity is Correcting oversteer on ovals: On an oval track or traction circle exercise, the seating position is brought much closer to the wheel to endure the almost constant G-Forces. This, however, makes it hard to impossible to apply large corrective steering inputs quickly. Therefore, if you don't get the slide worked out immediately, let go and allow the steering to do it's job. Letting go of the steering is also exceptable in big drifting angles. Correcting with the transmission If you accidentally shiftlock (I.E. Make a sudden and inapropriate downshift) or shortshift (resulting in understeer), you need to declutch and shift back into the appropriate gear. Correcting with the clutch is another technique, used on extremly slippery surfaces (smooth ice, epoxy skidpads, aquaplaning, etc...
Scenario 6: Martin Rowe (Rally driver) uses left foot braking to control the bias of the car to induce slight oversteer into the corner. By doing so he earns a better turn-in and, when he picks-up the throttle before the APEX, he achieves neutral handling ("No understeer, no oversteer"). Later on, he reaches greater angles to intentionally slide the car. By accelerating moderatly, he shifts weight back so that the car will eventually pull back, but also shifts weight off of the front tires, so that the effect of countersteering is slightly hindered and the car is held sideways for longer. The difference between both cases is the angle of slide -- in the first case, the slip angle is very small and the car is not thrown off course, thus a greater amount of power can be applied. In the second case, the car is thrown sideways and countersteering is nessecary to keep the car heading the right way, hence it's important to keep neutral throttle to make a faster correction.
TransitionsOversteer itself isn't all that dangerous, because the front is very likely to keep the car approximately at the same radius. However, it is time consuming, and -- if on the edge of the roadway, usually if oversteer results as a transition from power understeer -- there is a danger of the car's rear hitting an obstacle (which could than spin it's front away from the corner too, particularly if countersteering is involved). Additionally, there is the danger of the car regripping and pitching towards the center of the corner (appear in sharp corners), or losing control completly (usually in a transition from ploughing understeer), and being spun and ripped off from the road. However, the greatest risk is actually from the things oversteer can transit into. In Oversteer drills in Driver's Edge, that this driver has a hard time due to seating position, not looking where she wants to go while this one spins because she tries to shuffle her hands, and this one because she's slow in catching the tail. We should mention that these drills are performed at slow speeds, in RWD BMW's, and that the instructors tend to flick the transmission into neutral to block transmission of power and somewhat assist the correction, and even so the recovery is often quite late, so the correction method is far from ideal. Perhaps the most dangerous outcome of oversteer is the pendulum effect. Countersteering without proper timing for the second steering manuever and/or the throttle application, would cause the car to slide in the other direction. The pendulum skid is typically going to be more aggressive (about 1.5 times as much!) and unexpected, and harder to control since you already have the steering turned sharply in one direction. The car is already going to be off-line, so the opposite skid is likely to render it almost immediately off-road. Sometimes, the resonance is such that the force of the skid remains nearly identical as the car "wiggles" it's tail side-to-side, which is known as a tankslapper. It occurs when you steer the car off-throttle in just the right timing. Alternativelly, too strong a power application is going to cause the car to straighten back unsmoothly, called a "tankslapper." This is an undesired effect that causes needless loss of speed and a possible pendulum effect. A car can also transition into an understeer. This can occur when the driver countersteers off-throttle. The countersteering, if timed just right, will make the front roll out as to keep the whole car moving sideways (rather than spinning). As the car rolls, it will wipe off speed. As speed is reduced, the weight transfer to the front would be reduced and the car will eventually lose momentum. Sometimes, this will make the car understeer forward towards the inside of the corner. Excessive or untimed throttle applications can cause a similar effect. The solution is to reduce the steering lock and make necessary throttle inputs. If unhelpfull, the solution is to remove the steering input, brake and than steer back on track.
DriftingDrifting refers to a controlled and sustained sort of oversteer. While oversteer can be intentionally induced and recovered in any car, it can only be sustained for a relatively large duration of time, with a powerfull, manual rear-wheel drive (preferably with a front-mounted engine), equipped with a limited slip differential. The reason being that, in such a car, oversteer can be more easily caused due to power ("power oversteer"), by spinning the rear wheels, rather than by locking them by letting off of the power input ("snap oversteer"). Many four-wheel drive cars behave like rear-wheel drive due to the power bias, but since the front tires are also under power, it will be hard to induce a sustained drift. There are multiple methods of inducing a drift, rather than just brutally apply the power. It can be induced by any means that would either spin or lock the rear tires, and than sustained with power, the slide the car sideways through corners. It is not the fast way around, due to a constant lost of speed during skidding and spinning wheels, but it's also not mearly for the show. In sharper and tighter corners over slippery terrain, like in a Rally stage, a small amount of control oversteer will help to get the car around the tighter corners. Scenario 7: Tiff uses a basic powersliding technique. By getting hard on the gas, the rear wheels are overpowered and spin. By lifting-off, power oversteer is arrested, but the car is still sliding somwhat because of a forward weight shift (beneficial if you want to sustain the slide). Than, getting back on the gas slightly more gently keeps the rear wheels spinning and the car oversteering untill it runs out of momentum (again, a situation to be avoided in a race, but desired in a drift. Notice that without decreasing the power input, the car spins in spite of countersteering. Neutral handlingNeutral handling is a situation between understeer and oversteer. It is where all four wheels slip in unison. It is experienced when the driver enters the corner with the weight on the front (by trail braking) at just the maximum speed possible to take the turn neatly. After the wheel is turned, the car will briefly slide outside on all it's four wheels. This is neutral handling. Some people consider it an ideal situation for cornering and for car design. If the car is set to understeer at the limit, it will slide it's front wheels and push out of the corner, while the rear wheels still haven't fully exploited their grip. The opposite effect will be achieved when the car is oversteering. An oversteering car is also unstable under braking and while trail braking into the corner, and when accelerating out of it in a powerfull rear-wheel drive car (like professional race cars). If the car was to be neutral, it would exploit all of it's available grip and be slightly faster. However, a neutral car, other than being hard to design, will be even harder to control. It too will tend to be unstable under braking and when accelerating out of corners. Furthermore, once the car breaks loose neutrally, it will do so sliding laterally over all four wheels. This kind of slide occurs without any relative movement of one axle relative to the other, thus being hard to detect in time. It's better to make an understeering car that is slightly slower inside the corner, but is more controlled and allows to accelerate harder out of the corner. |