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Race Driving Fundamentals: Understeer

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00:00 - Understeer is probably one of the most disliked handling characteristics we'll come across in our cars and particularly if you're taking a street car to the racetrack, you're likely to find that understeer is the predominant handling trait that you'll be dealing with.
00:14 Understeer is simply where the front tyres of the car begin to slide or break traction before the rear tyres.
00:20 You may also hear the term push used to refer to understeer and these terms are interchangeable.
00:26 Understeer occurs when the car doesn't turn and follow the line you're expecting as you turn the steering wheel.
00:33 The car instead will literally under steer.
00:37 Instead of following the line you're intending, the car will run wide and push towards the outside of the track.
00:43 The fact that the car is understeering will be pretty apparent to you as the driver because the car won't respond to your steering input as you'd expect.
00:51 You can also get a feeling for what's happening with the front tyres by the feedback that you'll get through the steering wheel.
00:58 When the front tyres are providing a lot of lateral grip on the racetrack, you'll have a reasonable amount of resistance and feedback through the steering wheel.
01:06 The steering will feel heavy.
01:08 As the front tyres begin to loose grip, the steering wheel resistance tends to diminish.
01:13 This lightness in the steering wheel, coupled with a car that's running wider than our intended or expected line, are clear and obvious signs of understeer.
01:23 This is a good time to point out that since the steering wheel is our connection to the front wheels, one of the skills we need to build up is and understanding of what the steering wheel feedback is trying to tell us.
01:35 There's a huge amount of information that can be conveyed to the driver from the steering wheel resistance and interpreting this information lets the driver understand what the front tyres are doing and how much grip is available, allowing us to exploit the tyres to their maximum potential.
01:52 While rear wheel and all wheel drive cars are by no means immune to understeer, front wheel drive cars tend to be more susceptible to it because the front tyres have the job of doing both steering and applying power.
02:06 If steering and throttle application aren't managed correctly, it's easy to exceed the available grip, resulting in understeer.
02:14 No matter what driveline configuration a car uses though, the good news is that in general, understeer is fairly safe and easy to deal with.
02:23 It's relatively predictable and manageable for the majority of drivers since the natural instinct when a car is suffering from a lack of front grip is to back off the throttle which then transfers weight back onto the front tyres, helping to reinstate grip.
02:38 This is coupled with a reduction in speed which can reduce or eliminate the understeer.
02:43 This is why understeer is designed into factory road cars because it's much safer and easier for a novice driver to control than oversteer which we'll discuss in the next module.
02:54 While understeer is usually easy to manage, some novice drivers will feel the need to wind on more steering lock to try and correct the understeer.
03:03 Since we've already exceeded the available grip from the tyres, this additional lock does nothing to reduce the understeer.
03:10 Instead, this can actually result in a dangerous situation when all of the speed has been lost and the front tyres eventually grip up again, spearing the car off into the infield or causing a spin.
03:22 While car setup and suspension design is a big contributing factor to understeer and chassis balance in general, it can also be just as easily caused by the driver.
03:33 Two of the common causes of understeer at corner entry are trying to turn into the corner while still braking too hard or turning into the corner when the car is travelling too fast.
03:45 If we consider for example that the driver is braking at the limit of the available grip from the tyre, then there's no additional grip left to be able to generate lateral cornering force.
03:56 If the driver tries to turn into the corner while braking hard, the car is going to push wide of the intended line.
04:02 A reduction in braking pressure is essential to allow the car to turn in.
04:07 On the other hand, if the driver has arrived at the turn in point travelling too fast, then there's only so much lateral cornering force the tyres can generate and even if the driver is completely off the brake we may simply be expecting too much from the tyre.
04:21 Which end of the car will begin to break traction first under these conditions will depend on the car setup and driving technique but if the driver has released the brakes early, allowing weight to transfer to the rear of the car, understeer is the most common outcome.
04:37 The other situation where understeer is common is once the car is past the apex, and the driver is beginning to reapply the throttle.
04:44 This naturally results in weight being transferred towards the rear of the car and away from the front wheels.
04:51 Depending on the specifics of the car and the corner, this can result in the car understeering wide of the intended line.
04:58 In summary, the key concept to take away from this module is that understeer is where the front of the car will begin to break traction and slide before the rear.
05:07 This can be noticed by the car running wide of your intended line, coupled with the steering becoming lighter as the tyres lose grip.
05:15 Understeer can be a result of chassis setup or driver input, however fundamentally it's a result of insufficient grip on the front tyres when compared to the rear.
05:25 To correct understeer, we need to reduce the throttle input which will increase the available grip on the front tyres as well as reducing the speed through the corner, thus demanding less lateral force from the tyres.

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