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Thread: Oversteer

  1. #1
    WVSTREETS Guest

    Default Oversteer


    Oversteer an overview

    Oversteer, like understeer, results from the car reaching the limits of traction on a corner. In this case, the rear tyres reach the limit of adhesion before the front. This leads to 'the back coming out' (see Figure 1). The good thing about oversteer is that you normally go through the hedge backwards, thus preventing expensive repairs to the front of your vehicle! If you manage to performed sustained, controlled oversteer this is know as drifting.
    Figure 1: Oversteer in action (click to enlarge)

    A. The point of turn-in

    B.
    The car has turned in to the corner normally, all wheels are gripping effectively

    C.
    The rear wheels are starting to lose adhesion, the driver compensates by steering left to keep steering aligned to the desired driving line (counter steering, explained below)

    D.
    The car is at the limit of left hand lock, a spin is likely at this stage.
    Figure 2: A close up at position C in Figure 1

    Oversteer is more exciting than understeer and like most exciting things (such as jumping off cliffs) there is an element of risk involved. Most 'driver's cars' have a tendency to oversteer when on the limit around corners, and this property can be found in a variety of vehicle layouts and drive formats.
    Oversteer factors involved

    Oversteer results from a number of factors, some of which involve the natural handling characteristics of the car, and some result from the way it's being driven.
    Passive factors at work (the natural properties of the car):
    • Weight distribution (front or rear bias)
    • Engine and drive layout
    Active factors involved (the way it's being driven):
    • Cornering speed
    • Throttle
    • Braking
    • Steering inputs
    • Weight transfer
    Symptoms of oversteer

    It's unlikely you'll experience oversteer unless you're driving a car fast or the roads are slippery.
    • The rear of the vehicle becomes unstable and 'light' due to lack of grip
    • The car starts to rotate so driver is facing the inside of the corner
    Causes of oversteer

    There are four major active causes of oversteer, but what you're likely to encounter depends on the car being driven (for more information on this please skip to the next section). Causes include:
    1. Entering the corner too fast
    2. Accelerating into the corner, too early or too aggressively
    3. Braking into the corner or mid corner
    4. Lifting off the throttle mid-corner. This scenario is also known as:
      • lift off oversteer
      • snap-oversteer
      • trailing-throttle oversteer
      • throttle off oversteer
      • lift-throttle oversteer
    To view a blog post on lift off oversteer, please click here
    Oversteer and racing / performance cars

    Most performance cars have a tendency to oversteer as they are usually developed to provide a large amount of grip at the front wheels (to turn into corners well at speed), and a large amount of power (usually at the rear wheels). This means that if traction is lost it will usually be at the back first. See our grip section for more information. Thus in most cases the ideal cornering technique in a performance car needs to try and reduce or control oversteer.
    Preventing and correcting oversteer - rules of thumb

    To correct any form of traction loss, you need to consider why you've exceeded the limits of grip at the wheels. In all cases of oversteer, counter steering is also required (explained here).
    1. Entering the corner too fast
    Enter a corner too fast and you're asking for trouble. Unless of course you have a lovely long run off to play with or if you're driving Silverstone in a go-kart. Its not the quickest way to take a corner and leads to increased risk of oversteer. If you have entered a corner too fast, ensure that every input you make is incredibly smooth, and take the easiest route. Next time make sure you're entry speed is slow enough to maintain grip, you can build up speed as you gain experience.
    2. Accelerating into the corner, too early or too aggressively
    If you manage to break traction at the back when applying throttle, you're probably in a powerful car and need to be less aggressive. If you're spinning wheels, the power is not transferring to the road and you're not benefiting from the many horses you have sitting under the bonnet. Gently ease off the gas and you should regain adhesion at the rear wheels.
    3. Lifting off the throttle mid-corner
    If you are on the power mid-corner and close to the limit, do not lift off the throttle. The resulting forward weight transfer can upset the balance of the car and allow the rear wheels to break loose. In a front wheel drive car, re-applying the throttle can often help in this situation.
    4. Braking into the corner or mid corner
    You should avoid braking in corners in most situations, however there are circumstances which require the use of the anchors. Ensure braking inputs are especially smooth, gentle and progressive, and if a squirrel has just run out in front of you, try steering around rather then doing an emergency stop. To correct brake induced oversteer, smoothly (but rapidly) release the brake and adhesion should be reintroduced.
    Correcting oversteer - counter steering / opposite lock (use in all scenarios)

    Whatever the cause of oversteer it is important to keep the front wheels pointing in the direction you're hoping to go. If you fail to do this, the most likely result is a spin. This technique is known as counter-steering or applying opposite lock (see Figure 3). You should apply enough steering lock to point the wheels in the direction of the slide as shown below. Too little and you're likely to spin as the back continues to come round, too much and the car will rapidly over-correct, often resulting in a spin in the opposite direction. The skill can only be mastered with plenty of practice and should become instinct if you're planning to drive fast on a track.
    Figure 3: Counter steering / using opposite lock

    Oversteer and different drive / engine layouts

    Rear wheel drive
    In a rear wheel drive car you have the benefit of sharing the demands on adhesion between the front and rear wheels. The front wheels do the steering and the rear do the accelerating (and deceleration under engine braking). This usually results in a more balanced vehicle. In most conventional front engine, front wheel drive vehicles such as the Ford Fiesta it is rare to ever experience anything other than understeer.
    Rear wheel drive cars can experience oversteer for different reasons depending on where the engine is located.
    Rear wheel drive, front engine e.g. BMW M3, Mazda MX5

  2. #2
    WVSTREETS Guest

    Default Re: Track Racing- Oversteer

    Cause of oversteer
    Likelihood of oversteer
    Entering the corner too fast
    High
    Accelerating early or aggressively
    High
    Lifting off the throttle
    Med
    Braking
    Med
    In a front engine car, most of the weight is over the front wheels. This usually results in higher natural levels of grip at the front (which is useful for steering and braking). The comparatively unladen rear wheels may have lower natural levels of grip, which can lead to oversteer especially when accelerating round a corner. This is the reason some very high powered cars have wider wheels and tyres at the back.
    Question: When a front-engined rear-wheel drive car accelerates hard in a corner, there is a high possibility of oversteer. I also understand that weight is transferred to the rear under acceleration, therefore i would like to know how the rear wheels can still lose traction when weight is transferred to the rear and on to the rear wheels.
    Answer: There are many factors at work when cornering and its a fine balance of forces. Its important to understand that when youre cornering there is much less grip available for acceleration and braking. For a rear weight transfer to occur in the first place, you need to have the grip available to put the power down if you try to accelerate hard youre likely to overwhelm the rear tyres and spin one or both of the wheels. This reduces the physical grip dramatically which can then lead to oversteer.
    Rear wheel drive, rear engine e.g. Porsche 911

    Cause of oversteer
    Likelihood of oversteer
    Entering the corner too fast
    High
    Accelerating early or aggressively
    Med
    Lifting off the throttle
    High
    Braking
    High
    Rear engine, rear wheel drive vehicles such as the Porsche 911 can oversteer for different reasons to front engine varieties. In this case most of the vehicle weight is over the rear wheels, leading to greater levels of natural grip at the back, which should lead to an inherent low risk of oversteer. However, there is another force at work here momentum. Objects with greater mass carry more momentum and are harder to change direction at speed. In the case of rear engine cars, the rear has more momentum than the front which can lead to a greater risk of oversteer as a result of braking or lifting off mid corner.
    Mid engine cars can also oversteer for similar reasons, but tend to provide a better balance of under and oversteer.
    Front wheel drive (front engine) e.g. Peugeot 205 GTi, Renault Clio Cup

    Cause of oversteer
    Likelihood of oversteer
    Entering the corner too fast
    More likely to understeer initially
    Accelerating early or aggressively
    Low
    Lifting off the throttle
    High
    Braking
    High
    Sporty front wheel drive cars are more likely to experience oversteer than a standard car due to the vehicle setup. Dial out the inherent understeer tendencies of a front wheel drive car using clever engineering, and the result is a better 'turn in' and an increased ability to oversteer due to the naturally light rear. In this case, it is usually possible to accelerate out of the oversteer situation, using the rearward weight transfer to actively increase levels of grip at the back. Front wheel drive cars are especially prone to lift off oversteer due to the forward weight transfer combined with light rear end.
    Question: When a FWD car accelerates, weight is transferred to the rear. Does this mean that the front of the car where the engine is located becomes lighter than the rear during acceleration?
    Answer: Firstly, the weight transfers which result from acceleration are perhaps not as great as you think. This is because you're unlikely to be able to accelerate as quickly as you can brake or change direction with the steering - thus the advantages or rear weight transfers are usually slightly less than in other directions. It's very unlikely any front engine car could accelerate to the point that the rear weights more than the front. There will be some transfer of weight onto the rear wheels, but not that much.
    Four wheel drive e.g. Subaru Impreza, Nissan Skyline, Audi Quattro

    Cause of oversteer
    Likelihood of oversteer
    Entering the corner too fast
    Med
    Accelerating early or aggressively
    Med / High
    Lifting off the throttle
    Med
    Braking
    Med
    Four wheel drive vehicles can oversteer as much as rear wheel drive cars, depending on setup. However, due to the sharing of drive forces over all four wheels, there is less risk of oversteer due to too over-exuberance with the throttle pedal. Treat as a rear wheel drive vehicle and you won't go far wrong. With particularly powerful four wheel drive vehicles it may be possible to enter a 'four wheel drift'. This is a particularly spectacular way of exiting the road!
    An incredible four wheel drift in an Audi Quattro courtesy of www.bruze.nu

    Simple modifications to make a car less prone to oversteer

    If you have a track car and find oversteer a problem, you can complete some relatively easy modifications which can make the handling more neutral. These include:
    • Reducing the rear tyre pressure
    • Softening rear springs or anti-roll bar
    • Use softer rear tyres
    • Increase rear down force (if aerodynamics fitted)
    Disclaimer: Always stick to the manufacturers recommended limits when altering tyre pressures, and never modify a road car.

  3. #3
    Join Date
    Mar 2006
    Location
    Morgantown,wv
    Posts
    389

    Default Re: Oversteer

    oversteer is like crack. Its dangerous, addicting, gives you a high, and you wanna do it all the time. Unfortunately if you do it in the wrong place you will get arrested. Sometimes i like to sneak an oversteer here and then when i think noone is looking, but who doesnt????

  4. #4
    Join Date
    Mar 2006
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    Morgantown,wv
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    Default Re: Oversteer



    theres some of my fwd oversteer. lets see everyone elses

  5. #5
    Join Date
    May 2005
    Location
    Wheeling, WV
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    5,618

    Default Re: Oversteer

    brian did robbie vennimen use to have this honda....i know it's had more turns than a door knob around the grove

    224hp/280tq | 17lbs of boost | Neuspeed P-Flow Intake | Replacement Forge DV | EuroJet Boost Gauge
    "And remember kids, procrastination is like masturbation: in the end, you're just screwing yourself."

  6. #6
    Join Date
    Mar 2006
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    Morgantown,wv
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    389

    Default Re: Oversteer

    yeah.. car was beat when i got it.. i revived it.

  7. #7
    Join Date
    May 2005
    Location
    Wheeling, WV
    Posts
    5,618

    Default Re: Oversteer

    you gonna bring your civic up this year for some autoX?

    224hp/280tq | 17lbs of boost | Neuspeed P-Flow Intake | Replacement Forge DV | EuroJet Boost Gauge
    "And remember kids, procrastination is like masturbation: in the end, you're just screwing yourself."

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