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Extreme and defensive driving
Dmitry Aleksandrovich Liskin

The book is devoted to extreme and defensive car driving. The content is divided into two parts: В«defensive drivingВ» and В«extreme drivingВ». The first part is independent and is mainly aimed at mastering of defensive techniques. The second part is devoted exclusively to extreme driving and is aimed at developing driving skills, which will allow you to get the best lap time.

Extreme and defensive driving

Dmitry Aleksandrovich Liskin

В©В Dmitry Aleksandrovich Liskin,В 2021

ISBNВ 978-5-0053-7232-1

Created with Ridero smart publishing system

Introduction

Extreme and defensive drivingВ вЂ“ are strongly coupled driving styles, covering body ofВ knowledge about cars, its components and parts and how it works, driving experience and skills. Extreme driving means driving aВ car at its limit ofВ potential and learning basics sports elements (high-speed cornering, drifting, braking methods, study ofВ special terminology and so on) toВ achieve aВ minimum lap time. Defensive driving is focused on preventing crashes related toВ aВ partial loss ofВ control over car (for example, when the front wheels lose grip with the road inВ aВ corner).

Control aВ racing car is aВ mastery that takes years toВ master. Handling aВ sport car byВ aВ professional racer is comparable toВ virtuoso playing ofВ aВ musician on the guitar or piano. You ask: вЂњWhy do we need extreme and defensive driving skills, when we are either driving calmly inВ aВ straight line or standing inВ aВ city traffic jam?вЂќ The answer is simple: no one is immune toВ accidents on the road that can occur no matter what your driving style is. If aВ driver does not have the necessary skills, defensive driving techniques are not worked out and are not brought toВ automatismВ вЂ“ the driver can count on luck only.

Content ofВ the book is divided into two parts: вЂњdefensive drivingвЂќ and вЂњextreme drivingвЂќ. The material is built byВ an education course and is not difficult toВ master byВ aВ person, who has basic skills ofВ driving car and is familiar with how it works. The content includes:

вЂў tests results, their analysis and generalization;

вЂў descriptions ofВ operation ofВ car components, that affect behavior ofВ car and control techniques;

вЂў the techniques and methods ofВ extreme and defensive driving;

вЂў requirements for successful completion ofВ the driving techniques;

вЂў description ofВ the driving techniques inВ circuit racing;

вЂў aВ set ofВ exercises for self-training ofВ drivers and racers.

The book is not aВ collection ofВ postulates and canons, but is aВ help inВ mastering driving skills. The author is not responsible for road traffic accidents, related toВ aВ lack ofВ understanding ofВ operation ofВ car components, the driving techniques and their incorrect doing, with inappropriate technical characteristics ofВ cars and accidents caused byВ non-compliance with precautions when performing the exercises. All techniques should be performed after preliminary tests on the car and careful training ofВ the driver. The responsibility for driving lies entirely with the driver.

DEFENSIVE DRIVING

First part ofВ the book is independent and is mainly aimed at mastering ofВ defensive techniques. ToВ bring the techniques toВ automatism, at the ends ofВ the chapters exercises and tests are offered that simulate situations that may arise on the road. InВ the text ofВ the first part ofВ the book there are practical parts вЂњtestвЂќ for testing car and the defensive techniques and вЂњrequirementsвЂќ for successful completion ofВ the defensive techniques. Driving techniques are shown inВ the form ofВ flowcharts and marked with the letterВ M.

Front wheels sliding

The phenomenon when car not answers steering wheel turns, moves along straight trajectory (or trajectory begins toВ straighten) due toВ loss ofВ grip ofВ the front wheels on the road, is called understeer. Car shows understeer (low steerability), when the front wheels slide on the road.

The figure shows, how we entered aВ corner at aВ fairly high speed and pressed the brake pedal toВ the stop, which caused the front wheels toВ lock and, as aВ result, front wheels sliding.

Consider what happens with aВ contact patch ofВ the front tyres toВ the road when understeer due toВ heavy braking.

The figure schematically shows deformation ofВ aВ tyre during front wheels sliding, when the front wheels are turned byВ the steering wheel at aВ large angle. Contact patch is marked gray. When braking, load on the front axle increases, so contact patch also increases. When understeer, the tyre deforming, contact patch rotates toВ direction ofВ movement, and so-called tyre slip occurs. Tyre slip is angle ofВ twisting ofВ contact patch relative toВ direction ofВ movement ofВ the wheel. Steerability factor is defined as ratio ofВ rear wheels contact patch toВ front wheels contact patch. If front tyres deformation exceeds rear tyres deformation, steerability factor is less than one. InВ this case, they say understeer or low steerability.

Sliding ofВ the front axle is reflected inВ feedback ofВ the steering wheel. If at entry toВ aВ corner, the steering wheel turned with some effort, and after car stopped obeying the steering wheel and the steering wheel began toВ rotate more easily, then sliding ofВ the front wheels began. After the front wheels regain traction, feedback ofВ the steering wheel is also restored.

Sliding ofВ the front wheels is aВ cause ofВ accidents. Let us list causes ofВ understeer, which are related toВ driver errors:

вЂў too high speed or large angle ofВ turn ofВ the front wheels on entry toВ corner;

вЂў excessive braking during cornering (including wheels lock).

Common mistake: aВ driver over speeds at entry toВ aВ corner and, fearing that trajectory would not fit into borders ofВ the corner, turned the steering wheel deeper into the corner and pressed the brake pedal. If the front wheels are turned too much, they slide on the road. After pressing the brake pedal, the front wheels lock. InВ the end, trajectory becomes straight, car go out ofВ the corner or collides with aВ barrier.

When entering aВ corner at high speed you may feel that trajectory will not able be laid within the corner. When it seems that we do not fit into aВ cornerВ вЂ“ it is important not toВ lose your composure. InВ no case you should sharply hit the brakes and continue toВ turn the steering wheel inВ direction ofВ the corner, as these actions will only worsen the situation, there will be sliding ofВ the front wheels. It is necessary toВ depress the throttle pedal and start toВ slow down smoothly inВ the corner. Let us consider examples ofВ trajectories ofВ passing through aВ corner.

1В вЂ“ is вЂњidealвЂќ trajectory ofВ sports style cornering, 2В вЂ“ entrance toВ the corner was aВ high speed, 3В вЂ“ speed on the corner entry was so high that no chance toВ avoid way out ofВ the corner.

While driving along trajectory 2, speed ofВ car gradually decreased with help ofВ soft braking. Note that radius ofВ trajectory 2В gradually decreases, as with smooth braking speed ofВ car gradually decreases. It can also be seen that when driving along trajectory 2, car moves along outer edge ofВ the road, unlike trajectory 1. If the front wheels began toВ slide, trajectory 2В would straighten out and not fit into the corner. If at entry toВ aВ corner it is found that initial radius ofВ trajectory is too large, this does not means that it will not be possible toВ lay trajectory within the corner.

What can be methods ofВ dealing with front wheels sliding, if it still occurred?

1. If sliding is caused byВ braking, the first step is toВ depress the brake pedal. This should put control back inВ our hands.

After the wheels have regained their grip on the road, you need toВ start soft braking if you need toВ slow down.

2. If the steering wheel is turned at aВ too large angle, straighten it toВ restore grip ofВ the front wheels on the road. Speed ofВ car, grip ofВ the tyres on the road, turn angle ofВ the wheels are interrelated parameters. There is no point toВ turn the steering wheel at too large angle if car is not able toВ move along trajectory ofВ desired radius: instead ofВ small radius we get sliding ofВ the front wheels and straightening trajectory ofВ movement.

3. Drifting is controlled process, unlike sliding ofВ the front wheels. Therefore, it is possible toВ stop sliding ofВ the front wheels byВ drift. ByВ causing the rear wheels toВ slide, we regain control ofВ car. InВ addition, speed ofВ vehicle will fall during side sliding. There are various ways toВ cause the rear axle toВ slide. Let us look some ofВ them.

a) Sliding ofВ the rear axle can be triggered byВ using the handbrake. After sliding occurs, you need toВ turn the steering wheel against ofВ drift direction (against ofВ direction ofВ car rotation), so that car does not turn around. After speed ofВ movement drops, we restore trajectory.

b)В AВ small slide ofВ the front axle that occurs at exit ofВ aВ corner can be extinguished byВ sharply pressing ofВ the throttle pedal (this is used for aВ rear-wheel drive car only, sufficiently high engine torque is required).

ToВ eliminate understeer at exit ofВ the corner, we sharply pressed the throttle pedal. When the rear axle start drifting, we had toВ depress throttle pedal and turn the front wheels toВ the left toВ stop increase ofВ the drift. After that movement speed decreased.

c) Drifting ofВ the rear wheels on rear-wheel drive car can be caused byВ following method: press the clutch pedal, press the throttle pedal and gain high engine speed, then depress the clutch pedal without depressing the throttle pedal. After that, if engine torque is enough and it is sufficiently inert, the rear wheels should start slipping and the rear axle begin drifting. This technique can be used if there is shortage ofВ engine torque or time toВ perform receptionВ b).

Jerk traction created byВ aВ method b) -c) will cause drift ofВ the rear axle, slightly speeding up car. After drift occurs, you may depress the throttle pedal and try toВ stabilize car, winning distance from edge ofВ the road. It should be borne inВ mind that drift ofВ the rear axle is no less dangerous than slide ofВ the front axle. Therefore, you need toВ apply all the techniques consciously, after training and careful preparation.

During cornering there is aВ roll ofВ body and the wheels on outside ofВ corner are loaded with mass ofВ car, and on inside, on the contrary, they are unloaded.

Hereafter for brevity wheels, on which vertical load increases, we will call loaded, and wheels vertical load on which decreasesВ вЂ“ unloaded. When wheel is loaded, its grip on the road (friction force) increases, and when wheel is unloaded, its grip decreases.

Important note: limited slip differential may be required toВ cause rear axle drift due toВ the engine torque. ToВ provoke drift, the engine torque must be transferred toВ both loaded and unloaded wheels, which can be only byВ limited slip differential. If motor has low torque and differential has no internal friction, there may be difficulties inВ creating drift.

Consider the demonstration ofВ understeer on example ofВ emergency maneuvering, this is relevant for city conditions. Let us say that obstacle has appeared inВ our path while we are moving. Our task is toВ avoid obstacle and come toВ the stop without incident. ToВ simulate such situation, we will use aВ test inВ the form ofВ special markings and placed cones on the test ground.

Along the strip ofВ cones we will accelerate the car. After we achieve fixed speed (inВ this case, we will gain speed ofВ 75В km/h), we will move strictly straight along the strip ofВ cones toВ the vertical marking, without taking any action. As soon as we achieve the line, our hands will be untied, we will be able toВ perform any actions with the controls. Shaded areaВ вЂ“ is an area where may be obstacles. Hitting the shaded area or turn the car around will be considered as aВ failure. We need toВ avoid sector ofВ expected location ofВ obstacles and stop. Let us call this test вЂњundersteer testвЂќ.

So, the first test. We gain 75В km/h, after the line we brake, trying toВ go left the leftmost cone.

Pressing the brake until it stops caused the front axle toВ slide, and the car hit into the shaded area. If there was an obstacle, there would be collision. Aggressive braking during maneuvering is unacceptable. Now we are going toВ maneuver without braking. As inВ the previous test, we gain speed ofВ 75В km/h and move strictly inВ straight line, after the marking we try toВ perform the maneuver.

When we achieve the line, we depressed throttle pedal and turned the steering wheel sharply toВ the left. The car started drift and almost turned around. This is due toВ our car has high steerability. Return toВ the starting position and repeat the test. Now we work with the steering wheel more precisely and composedly.

We successfully went around the shaded area byВ depressing throttle pedal and working with the steering wheel only. After bypassing the danger zone, we braked toВ the stop.

InВ this test you can select geometric parameters: distance from vertical marking toВ the shaded zone and its length from the center ofВ the acceleration band.

For fixed dimensions, there is maximum speed at which car can pass the test. InВ this case speed was 75В km/h. At higher initial speed, the car inevitably hits into the shaded area.

Understeer and sliding ofВ the front wheels occurs, as rule, when driving cars that have low steerability. For vehicles with low steerability, sliding ofВ the front wheels is quite often.

Exercise 1. Provoke sliding ofВ the front wheels byВ locking the wheels with heavy braking, when moving around aВ ring or passing aВ corner. Depress the brake pedal and regain control ofВ car.

Exercise 2. Repeat previous exercise, but now press the brake pedal not toВ the end, aВ little weaker. Gradually reducing effort on the brake pedal, find optimal pedal position when the front axle does not slide and trajectory is maintained, but car reduces speed as quickly as possible.

Exercise 3. Provoke understeer byВ turning the steering wheel too much. Take control ofВ car back byВ slide ofВ the rear axle with handbrake.

Exercise 4В (for rear-wheel drive). Accelerate smoothly at exit ofВ aВ corner toВ get sliding ofВ the front wheels. Suppress understeer byВ causing the rear axle toВ drift with help ofВ engine power. This may be sharp press on the throttle pedal or spin ofВ engine with subsequent depressing ofВ clutch pedal.

Exercise 5. Place cones on aВ ground toВ perform the test described inВ this chapter. What is maximum speed at which car can pass your test?

Exercise 6. Moving at constant speed, turn the steering wheel toВ find position ofВ the front wheels, at which radius ofВ trajectory is minimal, but the front axle does not slide.

Exercise 7. Place cones on aВ ground that simulate aВ corner. Make long distance behind the cones, ensuring safe exit from the corner. Enter corner at speed at which the front wheels slide and car go out ofВ the corner. With help ofВ previously practiced techniques, extinguish speed at entrance toВ the corner toВ overcome slide ofВ the front axle.

Steerability

Steerability is one ofВ the most important characteristics ofВ car. InВ many cases behavior ofВ the vehicle can be described byВ the term ofВ steerability. SteerabilityВ вЂ“ is speed ofВ change the longitudinal direction ofВ the body when the steering wheel is turned while driving. Steerability shows how car will behave while moving after turning the steering wheel.

Steerability may be low, neutral, or high. Steerability affects the behavior ofВ car inВ corner and, as aВ consequence, the technique ofВ passing corner.

Let us run aВ couple ofВ tests. We will use two cars. The first is aВ retro car, aВ 1970В rear wheel drive sedan. Like many cars ofВ those years, it has aВ big and heavy engine, which is located inВ the front. The second is aВ modern 2011В front wheel drive hatchback with aВ lighter engine, which is also located under the hood inВ front ofВ the front axle. Fuel injection on the hatchback engine is carried out byВ injectors controlled byВ an electronic engine control unit. Torque ofВ this engine is lower and shifted towards higher rate (compared toВ the sedan engine), but the engine develops more power at high rate.

The tests will be carried out on aВ single corner. We will enter the corner at over speed, at which aВ car does not вЂњbuild inвЂќ the corner aВ little.

At the entry toВ the corner depress the throttle pedal and press the clutch pedal, after which we quickly turn the steering wheel all the way toВ the corner and keep the steering wheel inВ the full turned position. When speed drops below 10 km/h, press the brake and stop. First, we test the retroВ car.

After turning the steering wheel the car did not move along trajectory ofВ desired radius. The front wheels began toВ slide. You can see the tyre trace ofВ the left front wheel unloaded inВ the corner. Eventually, the car flew out ofВ the corner. When trajectory is straightened, there is slide ofВ the front axle and car cannot move along trajectory ofВ desired radius, it is said that car shows low steerability or understeer. Car with low steerability when maneuvering is disposed toВ sliding ofВ the front axle. When driving car with understeer, the body unwillingly turns after turn ofВ the steering wheel.

Now we mount the hatchback and repeat the same experiment.

We got trajectory with smaller radius. If you compare the final positions ofВ the bodies, the sedan body turned at angle less than the hatchback body.

InВ the modern car, inВ addition toВ sliding ofВ the front axle, began drift ofВ the rear axle, after which the car lost speed inВ drift and went inside the corner. This means that the carвЂ™s steerability is high. High steerability is accompanied byВ oversteer and sliding ofВ the rear axle. When you turn the steering wheel the body ofВ car with high steerability begins toВ turn quickly inВ the direction ofВ corner, and there is drift ofВ the rear axle.

Let us compare the characteristics ofВ the cars. The old sedan front track is less than the rear track, the hatchback has the conversely. The sedan has engine at the front, like the hatchback, but the base is longer, which means the center ofВ mass is moved away from the rear axle. The automobiles have different body typesВ вЂ“ sedan and hatchback. Thus, the steerability is affected byВ width ofВ the front and rear tracks, mass and its spacing. Let us look at some examples.

InВ race cars prepared for drag racing, the front track is less than the rear, and the heavy engine is at the front, at large distance from the rear axle. All this creates desired very low steerability. Besides, on the front axle ofВ these monstersВ вЂ“ are very light wheels with small diameter compared toВ the rear. The huge wheelbase allows you toВ accurately adjust trajectory.

InВ the rally hatchbacks with front and all wheel drive are popular. The front track is usually wider than the rear. The steerability ofВ the rally cars with these types ofВ drive is often high.

Cars prepared for oval racingВ вЂ“ are front engined sedans with large wheelbase and less the front track than the rear. Their steerabilityВ вЂ“ isВ low.

InВ circuit racing cars with different steerability are used, depending on type ofВ race track, driving style and preferences ofВ racer. Beginning drivers who participate inВ circuit races usually prefer stable and predictable car behavior and tend toВ choose low steerability. High steerability allows you toВ enter corners faster, but driving car with high steerability requires the racerвЂ™s driving skills and special car settings.

Let us sum up the results ofВ our tests and reasoning.

вЂў on car with low steerability it is easier toВ fly out ofВ the turn;

вЂў hatchbacks have higher steerability than sedans;

вЂў if the motor is distanced from the rear axle we get less steerability;

вЂў low steerability is priority for drag and speed racing, such as oval;

вЂў high steerability is well suited for non-speed tracks with lot ofВ corners.

Settings that result inВ reduce ofВ steerability:

вЂў narrow ofВ the front track and widen ofВ the rear track;

вЂў increase the front clearance and decrease the rear clearance;

вЂў increase deflection rate ofВ the front suspension springs and decrease deflection rate ofВ the rear suspension springs;

вЂў increase the bump and rebound resistances ofВ the front shock absorbers and decrease the bump and rebound resistances ofВ the rear shock absorbers;

вЂў increase the stiffness ofВ the front antiroll bar and decrease the stiffness ofВ the rear antirollВ bar;

вЂў use ofВ more hard front tyres and soft rear tyres;

вЂў increase pressure inВ the front tyres and decrease pressure inВ the rear tyres;

вЂў increase camber ofВ the front wheels and decrease camber ofВ the rear wheels;

вЂў increased toe inВ ofВ the front and rear wheels;

вЂў increase aerodynamic downforce ofВ the rear ofВ car and decrease aerodynamic downforce ofВ the front ofВ car;

вЂў increase side aerodynamic drag ofВ the rear ofВ car and decrease side aerodynamic drag ofВ the front ofВ car;

вЂў move the center ofВ mass toВ the front axle (distance the center ofВ mass from the rear axle);

вЂў decrease inertia moment (mass or diameter) ofВ the front wheels and increase inertia moment ofВ the rear wheels.

Opposite actions lead toВ increase ofВ steerability.

Influence ofВ the aerodynamic elements on car behavior strongly depends on speed ofВ movement. At low movement speeds effect ofВ the aerodynamics on behavior ofВ car is negligible. But at high speeds, when heavy air flows, influence ofВ the aerodynamics becomes significant.

InВ practice, as aВ rule, it is difficult toВ talk about neutral steeringВ вЂ“ this term exists inВ theory and mathematics. After tests, you can only tell what kind ofВ steering appropriate ofВ carВ вЂ“ understeer or oversteer and how pronounced oversteer is. Only theoretical calculations (we are talking about so-called steerability factor), which take into account large number ofВ variables, can accurately tell what kind ofВ steerability car has. Oversteer can be estimated qualitatively byВ angle ofВ drift or byВ distance between traces ofВ the unloaded inВ corner wheels ofВ the front and rear axles.

Besides drift angle, steerability can be evaluated byВ passing the following test.

Test ofВ steerability. Gain certain speed, press the clutch pedal and quickly turn the steering wheel toВ fixed angle. After vehicle is rotated 180В degrees, determine the distance between the starting and ending positions ofВ car.

Let us run this test on the hatchback and measure distance between initial and final trajectories.

As result the distance was slightly more than four lanes. If the greater distance obtained inВ the test, therefore, lower steerability. After changing vehicle settings (for example, spring rates, stiffness ofВ antiroll bars), you can repeat the test and compare the results. Initial speed and turn angle ofВ the front wheels must be the same. Steerability, which we have determined byВ methods described inВ this chapter, we will call steerability or steerability ofВ coasting motion.

InВ the tests we turned the steering wheel against stop (angle ofВ turn ofВ the wheels is about 40В degrees), the front wheels slide. If you turn the front wheels at aВ smaller fixed angle (10вЂ”15В degrees), drift angle (steerability) will be higher, since load on the front tyres will be less.

With help ofВ the controls, you can increase or decrease steerability. For example, if you press hard on the throttle pedal on rear wheel drive car while cornering, the rear axle can easily slides. That is pressing the throttle pedal on rear wheel drive car leads toВ acceleration not only, but also increases steerability. On front wheel drive car, on the contrary, pressing the throttle pedal causes car toВ straighten trajectoryВ вЂ“ this is effect ofВ reducing ofВ steerability. Oversteer (high steerability) may be created byВ using the handbrake: it is often possible toВ see drivers inВ rally races enter the hairpins with sliding ofВ the rear axle, locking the rear wheels.

Steerability created with help ofВ the controls will be вЂњaddedвЂќ toВ the vehicleвЂ™s steerability. Let us say if car has very low steerability, it will be more difficult toВ send it into drift due toВ traction on the rear axle than car with high steerability.

Exercise. Try toВ determine steerability ofВ your car. For this purpose you may place cones on ground that simulate aВ corner and do the test. Do not forget about safety: car can show very low steerability, or it can start slide and turn around, so there should be enough space on the ground.

Be careful! Incorrect вЂњtuningвЂќ ofВ car (it may be suspension parameters, track, ground clearance) can make your car unsafe. Manufacturers design passenger cars inВ such way that they are stable and do not roll over during sudden maneuvering. If there is aВ risk ofВ overturning inВ aВ corner, turn the steering wheel against the direction ofВ the corner toВ return vehicle toВ the four wheels.

It is worth noting that electronic drive control systems, electronic control ofВ torque distribution on the wheels, dynamic electronic motion stabilization systems can distort perceived steerability ofВ car.

Drift: causes ofВ origin and methods ofВ fighting

When the front axle slides, we lose control. Unlike understeer, driftВ вЂ“ is aВ controlled sliding ofВ car. There may be one or both axles inВ the slide. Tendency toВ drift and behavior ofВ machine when drift are influenced byВ such parameters as the type ofВ drive, steerability, the type ofВ differential. During drift, the rear axle tends toВ bypass the front. For clearness, if longitudinal direction ofВ the body deviates toВ the right from direction ofВ movement, we will say that car drifts toВ the right (drift direction is toВ the right), and angle between direction ofВ movement and longitudinal direction ofВ the body will be called drift angle.

This rear-wheel-drive car is specially prepared for drifting. It is equipped with limited slip differential, high torque motor, negative camber ofВ the wheels and an increased full lock angle ofВ the front wheels. On aВ front-wheel-drive car it is may be easily get out ofВ any angle ofВ drift, if engine torque is sufficient toВ maintain skid ofВ the front wheels. For example, on this car, we entered and exited drift several times one after another.

The sliding behavior ofВ an all-wheel-drive car depends on distribution ofВ the torque among the axles. If main part ofВ the torque is applied toВ the front axle, behavior ofВ car will be close toВ behavior ofВ aВ front-wheel-drive car. This all-wheel-drive car feels like aВ front-wheel-drive car: when pressing the throttle pedal the car tends come out ofВ drift.

But unlike front-wheel-drive, on all-wheel-drive car it is possible toВ maintain stable drift due toВ part ofВ engine torque transmitted toВ the rear axle. InВ addition it is easier toВ maintain aВ slide on all-wheel-drive car than on rear-wheel-drive car (with an appropriate ratio ofВ the torques transmitted byВ the engine toВ the front and rear axles), since traction on the front axle will not allow car toВ turn around.

It is worth noting, that when drive inВ reverse when turn the steering wheel the front axle can drifts. We accelerated inВ reverse and quickly turned the steering wheel, whereupon the car turned almost 180В degrees.

Inability toВ drive car inВ aВ drift often leads toВ accidents. Rear-wheel-drive car with usual differential (zero or low friction) is quite difficult toВ drive inВ aВ drift. Take for testing aВ rear-wheel-drive car with zero-friction differential (factory) on the rear axle. Let us look at what may be causes ofВ occurrence and ways toВ provoke rear axle drift.

1. Braking byВ handbrake. It is the simplest and most understandable cause.

2. Aggressive throttling on aВ rear-wheel-drive car. Please noteВ вЂ“ with aВ standard differential the first starts toВ skid wheel from the inside ofВ corner (the unloaded wheel).

3. Speeding ofВ engine and depressing the clutch on aВ rear-wheel-drive car. If you push the clutch, gain engine speed and, without releasing the throttle, release the clutch, the rear wheels will skid.

We revved up the engine and casted off the clutch pedal. The both rear wheels began toВ skip, the rear axle began toВ drift.

4. Engine braking on aВ rear-wheel-drive car. When the throttle pedal is released, firstly, the front axle is loaded and the rearВ вЂ“ is unloaded.

Because ofВ this grip ofВ the front tyres with the road increases, the rearВ вЂ“ decreases. Secondly, there is aВ braking effort on the rear wheels caused byВ engine braking. These facts lead toВ increase ofВ steerability and can cause drift when maneuvering on aВ rear-wheel-drive car, especially on aВ high steerability car. Soft braking with engine braking together can have the same effect. InВ addition, roughs on the road unload the rear axle awhile, which combined with engine braking increases risk ofВ sliding on aВ rear-wheel-drive.

5. Downshift without throttle blip on aВ rear-wheel-drive car with aВ manual gearbox. After lowering the gear and releasing the clutch pedal the engine is forced toВ gain speed inВ aВ short time distance, which can be indicated byВ aВ jump ofВ the tachometer needle. On rear-wheel-drive, this is equal toВ action ofВ the handbrake.

6. Braking with aВ strong shift ofВ brake balance toВ the rear axle. When balance ofВ the braking system is shifted toВ the rear axle, steerability may increases during braking. It may happen that the rear wheels will be first toВ brake.

7. Rocking the center ofВ mass. Rocking can cause drift when passing an S-like corner.

When direction ofВ movement changes, the energy stored inВ the compressed suspension, is freed and pushes car inВ opposite direction, which can lead toВ drift.

8. Together pressing the throttle and brake pedals on aВ front-wheel-drive car. Moving along the ring on aВ front-wheel-drive car, let us press the throttle and brake pedals at one time.

There was drift ofВ the rear axle, the car rushed inside the ring. That is, the pressed throttle and brake pedals on aВ front-wheel-drive car create oversteer. Since we pressed on the throttle when braking, there was traction from the engine on the front axle. The rear axle brakes more intensively than the front, not exclude the rear wheels may be locked. Braking byВ the rear wheels creates oversteer, which is similar toВ braking byВ the handbrake. ToВ describe operation ofВ the front axle we take into account the several factors:

вЂў due toВ the roll inВ the corner the left wheels were loaded with mass ofВ the car, and the right wheels were unloaded;

вЂў the front wheels are affected byВ the engine torque and braking effort;

вЂў the engine torque is divided between the front wheels byВ the differential.

On the front axle ofВ the car aВ zero-friction differential is installed, which transmits half ofВ the engineвЂ™s torque toВ the each wheel. ToВ explain the test results, we assume that the engine torque is enough toВ maintain traction on the front wheels when the brake pedal is pressed full way down.

For demonstrativeness ofВ illustrations we introduce the concept ofВ equivalent force. Equivalent force is the force that must be applied toВ the top ofВ wheel toВ obtain the torque on wheel (this may be engine torque or torque generated byВ aВ braking system).

The figure shows the force was applied toВ the top ofВ the wheel and compels the wheel toВ rotate faster clockwise.

Let us draw equivalent forces that occurred when one time press the throttle and brake pedals inВ the previous test.

At the left figure black arrows indicate equivalent forces created byВ braking system, white arrowsВ вЂ“ equal equivalent forces corresponding toВ torque produced byВ the engine and is divided between the wheels byВ differential. The right figure shows the resulting equivalent forces on each front wheel, which corresponds toВ the resulting torque (difference between engine torque and brake system torque). We did not press the brake pedal toВ the end, the braking effort on rear loaded wheel was not enough toВ lockВ it.

If braking effort is high enough, the rear wheels may become locked. Let us imagine aВ case when the rear wheels are locked. Note the locked wheels with crosses.

Direction ofВ the equivalent forces corresponds toВ direction ofВ movement ofВ the front wheels. Front unloaded wheel has worse grip on the road than the loaded one, and there is aВ chance that it starts toВ slip. If the unloaded wheel starts toВ skid, the main part ofВ the engineвЂ™s power will be transferred toВ it.

Although pressing the throttle and brake pedals creates oversteer on aВ front-wheel-drive car, steerability may be reduced byВ engineвЂ™s torque. If the rear wheels are locked, but the engine has an enough high torque, car will not turn around inВ aВ drift due toВ high traction on the front wheels. At the same time, if braking effort on the front wheels is fully compensated byВ the engine torque, maximum steerability will be achieved.

Increased friction ofВ differential allows you toВ transfer more torque toВ loaded front wheel and thus more efficiently implement engine power. Let us represent equivalent forces, when aВ limited slip differential is set on the front axle.

The left figure shows equivalent forces generated byВ braking (black arrows) and engine torque (white arrows). Figure on the right shows resulting equivalent forces on the front wheels after subtracting the braking effort from engine torque. AВ greater amount ofВ torque on loaded front wheel means that more engine power will be transferred toВ the wheel compared toВ situation, when aВ zero-friction differential was installed.

Thus, traction on the front wheels when braking creates oversteer. Presence ofВ aВ small traction on the front wheels during braking is equivalent toВ shifting balance ofВ braking effort toВ the rear axle. But too much traction on the front wheels can lead toВ straightening ofВ trajectory (understeer).

InВ addition toВ the previous reasons, drift can be caused byВ aВ sharp change inВ the road surface. For example, if aВ driver inadvertently drove aВ rear wheel toВ wayside ofВ the road on which there is ground or snow, car can drift. An inexperienced driver, as aВ rule, does not operate with information about condition ofВ the road surface and how it should affect the braking path and control technique. If you move inВ the вЂњnormalвЂќ tempo, familiar for dry weather, aВ rear-wheel-drive car can easily start drift at exit ofВ corner on aВ wet road. Another danger may be invisible ice under the snow. Unsuspecting driver moving quite calmly on the road or passing aВ corner, can hit into emergency situation.

You can create oversteer inВ all the ways that you can create rear axle drift. For example, shifting the brake balance toВ the rear axle will increase steerability when braking at entry toВ aВ corner. On aВ front-wheel-drive car steerability can be improved byВ using the throttle and brake pedals together.

Ways toВ go out ofВ drift

Front-wheel-drive

Consider ways toВ get out ofВ drift. At first consider the front-wheel-drive type. We will provoke drift byВ the hand brake. When the rear axle begins drift, we must press the throttle pedal toВ 100% and direct the front wheels against direction ofВ drift toВ stop the drift.

There are noticeable traces left byВ locked rear wheels during the action ofВ the handbrake. The first was locked the unloaded wheel. After the end ofВ handbrake action, the throttle pedal was pressed and the steering wheel was turned against ofВ the drift direction. It may be seen unloaded front wheel began toВ grind after pressing the throttle pedal. This is explained byВ the fact the machine has aВ zero-friction differential. Before the end ofВ the drift the steering wheel was returned toВ the вЂњstraightвЂќ position, after the throttle pedal was released.

The psychology ofВ an untrained driver forces him toВ release the throttle pedal when aВ drift occurs, regardless ofВ the drive type. This is aВ common error inВ driving aВ front-wheel-drive car. Finding himself inВ an unfamiliar situation, overcame byВ sense ofВ fear, the driver releases the gas pedal. So the drift increases. Eventually, driver loses control over the car, the car continues toВ move byВ inertia, as if there is no driver inВ it.

For successful exit from any angle ofВ drift on aВ front-wheel-drive car engine torque must be enough, toВ keep skidding ofВ the front wheels at least on the first gear, otherwise the engine will fail. If drift angle ofВ 90В degrees or more occurs it is likely, that you will have toВ lower the gear, toВ increase torque on the front wheels.

Rear-wheel-drive

On aВ rear-wheel-drive car the throttle pedal must be released when exiting from drift. Let us take aВ rear-wheel-drive understeer car. We will provoke drift ofВ the rear axle byВ pressing the throttle pedal roundly when passing aВ corner. ToВ stop drift, depress the throttle pedal and turn the steering wheel against ofВ drift direction. When drift begins toВ decrease, we will immediately return the steering wheel toВ the вЂњstraightвЂќ position.

When exiting aВ drift with help ofВ steering the maximum drift angle from which you can exit depends on the maximum turn ofВ the front wheels. Note that during exit from drift, the front wheels ofВ the car are directed along the direction ofВ movement. If aВ zero-friction differential is installed on the rear axle and no friction is created inside the differential when negative load, then braking byВ the engine will create noticeable oversteer. Therefore, inВ the case ofВ zero-friction differential, it is better toВ squeeze the clutch during fight with drift, toВ exclude engine braking.

At next, we will try an experiment. Let us see, what happens if press together the throttle and brake pedals, while the car is inВ aВ drift.

During pass the corner we provoke drift byВ throttling. Then we hit the throttle and brake pedals at the same time. The front wheels were locked, and there was traction from the engine retained on the rear wheels. Rear unloaded wheel began toВ skid. Trajectory straightened and drifting stopped. There are visible tyre traces, left byВ locked front wheels and unloaded rear wheel, which slipped on the asphalt.

Consider what happened toВ each axle when the throttle and brake pedals were pressed together. Since the drive is carried out on the rear wheels, the front wheels will only be affected byВ the braking effort, which causes the front wheels toВ lock. Locked front wheels cause understeer. Now let us look at what happens toВ the rear axle. For now imagine, that the rear axle has aВ zero-friction differential. The rear wheels will have braking efforts and equal engine torques.

The left figure shows equivalent forces, created byВ braking (black arrows), and equivalent forces, caused byВ engine torque (white arrows). At the right figure the resulting equivalent forces on the rear wheels are shown inВ white arrows. High braking effort on the front wheels locked them. On the rear axle aВ small traction was retained. As you know, traction on the rear wheels leads toВ loading the rear axle and unloading the front. ToВ lock the front wheel is easier, when the front axle is less loaded. As aВ result, conditions for understeer are created.

The torque on the rear axle can be adjusted so that the braking effort is compensated: neither traction nor braking effort will act on the rear wheels. InВ this case only the front wheels will brake, which is similar toВ aВ strong shift ofВ brake balance toВ the front axle. As for power, it is distributed unevenly between the wheels: zero-friction differential transfers the main part ofВ engine power toВ the unloaded wheel.

At the figure the arrows show the power transmitted toВ the rear wheels.

The torque on unloaded rear wheel causes it toВ spin rapidly and skid on the road surface. When the trajectory gradually straightens and roll ofВ the body decreases, the unloaded wheel regains grip on the road, speed ofВ rotation gained byВ it decreases sharply. At that there is aВ push against the direction ofВ drift, which causes the trajectory toВ straighten even more.

If aВ high-friction differential is installed on the rear axle, more engine torque will be transmitted toВ rear loaded wheel, than toВ rear unloaded wheel. When the throttle and brake pedals are pressed at the same time, there will be less understeer, than inВ the case ofВ aВ zero-friction differential, since the increased torque on rear loaded wheel will push the car inВ the direction ofВ increasing drift.

The figure shows the total equivalent forces, when aВ high-friction differential is installed on the machine. AВ high-friction differential transfers more than half ofВ engineвЂ™s torque toВ rear loaded wheel. The increased traction on rear loaded wheel pushes the car even deeper inВ the direction ofВ drift (toВ the left inВ the figure plane). An addition increase ofВ the torque on rear loaded wheel leads toВ an increase ofВ engine power transmitted toВ this wheel.

Thus, the same time pressing the throttle and brake pedals on aВ rear-drive car creates understeer and allows you toВ get out ofВ drift. InВ the future this method ofВ fighting with drift on aВ rear-wheel-drive car will be called aВ defensive вЂњthrottle+brakeвЂќ technique. As aВ rule, at drift angle ofВ approximately 45В degrees (the angle must be checked for each car) and more вЂњthrottle+brakeвЂќ technique does not work, since traction on rear loaded wheel causes car toВ turn around.

It is important toВ understand, that вЂњthrottle+brakeвЂќ technique forced aВ car toВ move straight. When performing the technique drifting stops, the machine continues toВ move inВ aВ straight line inВ the same direction, inВ which it was moving before performance the technique. Therefore it is necessary toВ calculate trajectory and duration ofВ вЂњthrottle+brakeвЂќ pulse. If aВ driver has reacted toВ drift inВ time, aВ short impact on the brake pedal and steering correction may be enough. Note, that вЂњthrottle+brakeвЂќ technique allows you toВ get out ofВ drift, without turning the front wheels.

Since the front wheels are locked, it does not matter, which way they are turned. But toВ successfully take control at the end ofВ the technique, when the front wheels are inВ locked condition, you should put the steering wheel straight. There are two reasons for this:

вЂў the suspension geometry is such, that when the front wheels are turned byВ the steering wheel, the front ofВ car come down; the straighten wheels will lift the front ofВ car back; the greater front clearanceВ вЂ“ the lower steerability;

вЂў if the front wheels are set inВ the straight position, car will remain neutral behavior after releasing the throttle and brake pedals (the carвЂ™s behavior will not change).

At the end ofВ вЂњthrottle+brakeвЂќ technique it is enough toВ align trajectory with aВ corrective steering. If it is necessary toВ avoid an obstacle or bend trajectory because ofВ other reasons, you should turn the front wheels previously, during perform the technique, when the front wheels are locked.

The torque transmitted toВ rear loaded wheel depends on engine torque. If engine torque is high enough, efficiency ofВ вЂњthrottle+brakeвЂќ technique may fall: when together pressed the throttle and brake pedals the rear wheels start toВ skid. InВ this case toВ exclude skidding ofВ rear loaded wheel, you should limit effort on the throttle pedal during performance the technique.

For вЂњthrottle+brakeвЂќ technique toВ work on aВ rear-wheel drive car, the brake system must be properly configured. It is necessary, that both front wheels are locked when the brake pedal is fully pressed both when moving forward inВ aВ straight line, and when passing corners toВ the left and right or when the car is inВ aВ drift. InВ addition, the braking effort on the rear wheels should not be too high, and engine torque should not be too low. If the rear wheels will be locked, the engine will stall.

Requirements for successful exit from aВ drift on aВ rear-wheel-drive car with help ofВ вЂњthrottle+brakeвЂќ technique

вЂў both front wheels must lock when the car is inВ aВ drift;

вЂў the rear wheels must not be locked;

вЂў skid ofВ rear loaded wheel should not occur;

вЂў differential friction should not be too high;

вЂў drift angle should not be greater, than about 45В degrees.

The last two requirements are very conditional. Performing ofВ the technique may differ on different machines, so you need toВ perform concrete tests. It is not difficult toВ test вЂњthrottle+brakeвЂќ technique: you just need toВ provoke aВ drift and press the throttle and brake pedals.

It was not said, but was obvious, that toВ perform the above-listed techniques an anti-lock system should not be installed on car, which prevents the wheels from locking byВ the brake system. InВ the presence ofВ an anti-lock system it is impossible toВ perform defensive вЂњthrottle+brakeвЂќ technique on aВ rear-wheel-driveВ car.

Recommendations for driving aВ car inВ aВ drift

вЂў while driving car inВ aВ drift, your hands should be relaxed, you do not need toВ hold the steering wheel with aВ death grip;

вЂў while drift turn your head and direct your gaze along the direction ofВ movement ofВ car, keep the hood inВ the background, so you will definitely feel angle ofВ drift;

вЂў when fighting with aВ deep drift direct your gaze forward, through the windshieldВ вЂ“ this will help you maintain your orientation inВ space.

Notes on performing ofВ вЂњthrottle+brakeвЂќ defensive technique on aВ rear-wheel-driveВ car

вЂў during perform the technique you should toВ straighten the front wheels or turn them byВ the steering wheel inВ the direction, inВ which you want toВ continue move at the end ofВ the technique;

вЂў if the engine torque is quite high and the rear wheels start toВ skid when performing the technique, you need toВ limit effort on the throttle pedal: the traction on the rear axle is only needed toВ unload the front;

вЂў the duration ofВ the technique is controlled according toВ trajectory ofВ movement.

Exercise 1. Work out the skills ofВ getting out from drift with help ofВ steering. Actions will vary depending on the type ofВ drive: on front-wheel-drive type it is necessary toВ increase the traction and toВ turn the steer against direction ofВ drift, on rear-wheel-driveВ вЂ“ you need toВ let go ofВ the throttle pedal, press the clutch pedal and direct the front wheels inВ the direction ofВ motion (you should toВ rotate the steer against the direction ofВ drift until desired position ofВ the front wheels).

Be careful! When exiting aВ drift on aВ rear-wheel-drive car there should not be aВ long pause after turning the steer against direction ofВ drift. Otherwise there may be aВ response from the car, and there will be aВ rhythmic drift. As soon as drift has started toВ stop, you need toВ immediately return the steer toВ the вЂњstraightвЂќ position.

Exercise 2. Create oversteer on aВ front-wheel-drive car at the entrance toВ aВ long corner (arc) with help ofВ вЂњthrottle+brakeвЂќ technique. Repeating the training, try toВ gradually increase speed ofВ entering the corner.

Exercise 3. On aВ rear-wheel-drive car, press the throttle pedal at the exit ofВ aВ corner, toВ trigger drift. Without releasing the throttle pedal, sharply hit the brake pedal with your left foot, toВ eliminate the drift. After stopping drifting release the pedals and restore trajectory byВ the steer motions. Repeating the exercise, determine angle ofВ drift, more than which the technique вЂњthrottle+brakeвЂќ does not work. Limit effort on the throttle pedal if there is aВ skid ofВ rear loaded wheel and efficiency ofВ вЂњthrottle+brakeвЂќ technique decreases.

Remember that on aВ front-wheel-drive car one time pressed the throttle and brake pedals increases steerability, while on aВ rear-wheel-drive carВ вЂ“ they decrease it. If this is the first time when you are perform the technique, limit speed and provide braking distance enough inВ all possible directions.

Exercise 4. On rear-wheel-drive or all-wheel-drive cars, prepared for drift, the exercises вЂњringвЂќ, вЂњeightвЂќ and the passage ofВ aВ hairpin with drift ofВ the rear axle will be useful. Rings should be selected inВ different diameters toВ work out different speed modes.

We press the throttle pedal with pulses, as if groping for optimal traction, and at the same time we steer. Our goal will be aВ stable retention ofВ trajectory radius and minimal fluctuations inВ drift angle.

Exercise 5. Go through aВ 180-degree turn (hairpin) with the rear axle drifting. At entrance toВ the corner provoke drift byВ rocking, handbraking or including aВ low gear.

At exit ofВ the corner maintain drift byВ alternately pressings the throttle pedal. Try toВ get maximum acceleration at exit ofВ the hairpin.

Exercise 6. Another useful exercise for training driving aВ car inВ aВ drift is the вЂњeightвЂќ. InВ the middle ofВ the eight we perform the so-called reversal: we accelerate car, then release the throttle pedal and rotate the steering wheel inВ the opposite direction when moving toВ the next half ofВ the eight.

If there is feedback on the steer it should start toВ rotate itself against the direction ofВ drift. The feedback force depends on the castor inВ aВ car and settings ofВ the feedback force inВ aВ car simulator.

Exercise 7. Try toВ cause the front axle toВ drift while reverse moving byВ sharply turn ofВ the steer. Do not forget toВ squeeze the clutch, so that the engine does not stall during skidding.

Practical advices for aВ driver

1. Use light footwear with soft, non-thick, flat soles for driving. Rightly chose footwear will help you feel the pedals better. InВ any case do not drive aВ car inВ вЂњflip-flopsвЂќ, slippers or shoes with aВ long heel, this can lead toВ an accident situation. If footwear has aВ heel, it should not be long. Shoelaces are also dangerous. Scarves, ties, long sleeves, hair, and wired headphones can also interfere for driving.

2. Wear gloves while driving. InВ gloves with aВ rubberized palm (so-called вЂњdippedвЂќ gloves) or leather gloves hands cling better toВ the steering wheel and the gear lever, and hand tires less during driving. If you are aВ novice racer, you may get В« dippedвЂќ gloves for training, which you can buy at any building supplies store.

3. Place your hands on the steering wheel at 9В and 15В oвЂ™clock or 10В and 14В oвЂ™clock (according toВ the clock face). InВ these positions you can comfortably rotate the steering wheel within about 200В degrees. If you need toВ turn the steering wheel at aВ greater angleВ вЂ“ continue rotation ofВ the steer with change ofВ hands position. AВ steering error will be crossing ofВ hands inВ the lower sector ofВ the steering wheel.

4. Use right steering wheel. Spokes ofВ the steer should not prevent hands from being placed inВ the 9В and 15В oвЂ™clock or 10В and 14В oвЂ™clock positions and fingers from squeezing the steering wheel inВ these positions. It is possible placing ofВ the spokes, inВ which they pass under or above handsВ вЂ“ so you will feel right position ofВ hands on the steer. It is not recommended toВ use aВ steering wheel cover, as it will dull feels, received from the steering wheel.

5. Take into account condition ofВ the road surface toВ choose speed ofВ movement. Let us assume, that you are on an unfamiliar road or road state may have changed significantly recently due toВ weather conditions. You may estimate condition ofВ the road surface with help ofВ braking with wheels locking. At low speed (10вЂ”15В km/h), hardly press the brake pedal toВ lock the wheels, and wait for stop. The worse the grip, the greater braking distance. When you get more experience aВ short-time wheels lock will be enough toВ estimate aВ road surface. This skill is very useful inВ winter: for example, aВ situation may be when the road is snow covered, and thereВ вЂ“ is bare ice under the snow, which aВ driver does not suspect.

6. Do not listen toВ music when driving. This takes away your attention and impairs your concentration on driving. The same applies toВ conversations on cell phone. AВ missed beep or even aВ scream can cause inconvertible events.

7. Do not move inВ neutral gear. Some drivers, trying toВ save on fuel, move downhill and enter corners inВ neutral gear. This makes driving aВ car unsafe. Disconnecting the engine from the transmission makes it impossible toВ control aВ car with help ofВ engineвЂ™s torque. The throttle pedalВ вЂ“ is aВ very important element ofВ controls inВ both front-wheel-drive and rear-wheel-drive vehicles.

8. Do not keep your hand on the gear lever. Many drivers drive inВ city traffic aВ car with aВ standard gear box inВ aВ relaxed pose, when left hand is on the steering wheel and right handВ вЂ“ is on the gear lever. Both hands should be placed on the steering wheel. Right hand moves toВ the gear lever only when it is necessary toВ change the gear.

Turnaround while reversing (police turn)

Police turn is familiar toВ many from films. It is rumored that drivers ofВ the special services keep it on board. Police turn allows you toВ quickly turn aВ car around with help ofВ front axle drift, which can be created while driving inВ reverse.

Despite seeming from the outside difficulty ofВ the technique, it is quite simple toВ perform. Consider performing the technique on front-wheel-drive and rear-wheel-drive cars.

Rear-wheel-drive

Firstly it is necessary toВ select the reverse gear and accelerate along aВ straight section ofВ trajectory. It should be noted, that during reversing after releasing the throttle pedal the engine starts braking. Engine brakingВ вЂ“ is aВ braking torque (some kind ofВ braking effort). Braking on the rear axle while driving inВ reverse creates understeer, similar toВ how high braking effort on the front wheels causes sliding ofВ the front axle when driving ahead. Therefore after performing acceleration it is necessary toВ disconnect the engine and transmission before performing the technique.

ToВ produce drift ofВ the front axle, you need toВ quickly turn the steer. After drift occurs, wasted no time, it is necessary toВ immediately return the steer toВ the straight position. When longitudinal speed will be zero, the first gear can be switched on. Let us show at the figure performance ofВ turnaround.

Initially we were moving inВ aВ straight line inВ reverse, but deviated from the straight line and after performing turnaround left the marked lane. Drifting ofВ the front axle did not begin immediately: at beginning turn ofВ the steer the car deviates from straight trajectory.

ToВ stay inВ the lane, during acceleration it is needful toВ slightly deviate from straight line movement with aВ short movement ofВ the steer toВ the side, opposite toВ direction ofВ turning. It is important toВ do this during accelerationВ вЂ“ if there is no traction on the rear axle when the steer deviates from the вЂњstraightвЂќ position, the car will start toВ turn around. Preliminary shift inВ the opposite side not only increases space for maneuver, but also intensify further sliding ofВ the front axle due toВ rocking. Let us show at the figure performance ofВ reverse turn with aВ preliminary deviation.

As you can see, we succeed toВ stay within the marked lane.

If aВ car does not respond well toВ performing police turn, you can use at one time pressing ofВ the throttle and brake pedals. Engine torque, transmitted toВ the rear axle, will prevent the rear wheels from braking, but high braking effort on the front wheels will lock them, causing aВ car toВ turn around. Let us illustrate at the figure reverse turn perform using the throttle and brake pedals.

Front-wheel-drive

On aВ front-wheel-drive car engine braking when reversing creates oversteer. We should seize this. But so that the engine does not stall during perform the technique, it is necessary toВ press the clutch, when engine speed drops toВ idle. Let us show at the figure performing aВ turnaround on aВ front-wheel-driveВ car.

Preliminary deviation should be performed byВ aВ very short and smooth steer motion, as aВ car may start toВ turn around. On rear-wheel-drive traction on the rear axle protects from turning, which is not present on aВ front-wheel-drive car during acceleration.

Regardless ofВ the type ofВ drive, some machine settings contribute toВ perform ofВ turnaround. Shifting the center ofВ mass toВ the rear axle (aВ small proportion ofВ the weight on the front axle) will make it easier turn ofВ the front axle around the rear axle. Besides, the more aВ car shows understeer when driving ahead, the more oversteer will occur when driving reverse. Therefore understeer will be another positive point for performing aВ police turn. So, factors, that affect steerability when driving inВ reverse are as follows:

вЂў shifting the center ofВ mass toВ the rear axle;

вЂў understeer when moving ahead.

Steerability when moving reverse affects on success ofВ turnaround performance. AВ turnaround while reversing can be performed with help ofВ aВ rightly set ofВ the brake system.

Exercise 1. Try toВ perform aВ police turn on aВ rear-wheel-drive vehicle inВ all the ways, described inВ this chapter. Which ofВ the ways toВ perform aВ turnaround is the most optimal for yourВ car?

Exercise 2. Perform aВ police turn on aВ front-wheel-drive vehicle. Be careful when performing aВ preliminary deviation, as front-wheel-drive vehicle shows oversteer during reverse acceleration (opposite toВ aВ rear-wheel-drive vehicle, which shows understeer during reverse acceleration).

Exercise 3. What settings must be changed, toВ increase carвЂ™s steerability when reversing? Test steerability ofВ reversing at different settings.

Return from an obtuse drift angle

Turnaround ofВ aВ car on the road is unlikely, but it can be quite dangerous, if it happens for some reasons when moving at high speed. When sliding at aВ large angle (90вЂ”180В degrees), it is impossible toВ control trajectory ofВ movement and predict behavior ofВ machine. An untrained driver will not be able toВ take any correct actions during turnaround ofВ aВ car toВ overcome drift.

It is known, that on aВ front-wheel-drive car it will not be difficult toВ get out ofВ almost any drift angleВ вЂ“ it is just needful toВ press the throttle pedal and turn the steer. For aВ rear-wheel-drive car there is an effective вЂњthrottle+brakeвЂќ technique, but drift angle, which can be overcome byВ this technique, is limited. Regardless ofВ the type ofВ drive, machine can be quickly returned, using dosed braking effort inВ definite range ofВ drift angles.

Let us try an experiment. We will move around aВ ring inВ reverse. While moving, press the brake and clutch pedals all the way down.

The sports carвЂ™s braking system is very powerful and can lock both the front and rear wheels. After pressing the clutch and brake pedals all the wheels locked, and the car continued toВ slide move inВ aВ straight line. The front wheels locked aВ little earlier than the rear ones. The final position ofВ the body is at small angle relative toВ the initial position. Let us repeat the test with less effort on the brake pedal.

When the brake pedal was pressed, both the front wheels and rear left wheel locked. The car almost turned around. If initial speed ofВ movement was greater, the car would most likely perform aВ turnaround before stopping. Braking efforts on both rear wheels are the same, but at the beginning ofВ braking weight ofВ the car puts more pressure on rear right wheel, than on rear left wheel. Therefore braking effort, which should lock right rear wheel, must be higher, than braking effort on the rear left wheel. InВ the next test we will push the brake pedal even more weakly, but we will try toВ provoke lockage ofВ the front wheels.

After pressing the brake pedal both front wheels locked, both rear wheels rotate, until the car stopped. The results are similar toВ the previous test: the car began toВ turn around after pressing the brake pedal. On all cars, as aВ rule, brakes ofВ the front wheels are much stronger than brakes ofВ the rear. If the brake system is correctly set, when the brake pedal is fully pressed when moving on an asphalt road inВ reverse inВ aВ corner or inВ an obtuse slide angle both front wheels must lock, and the rearВ вЂ“ continue toВ rotate.

Based on the previous experiments, let us formulate test for performing aВ car turnaround with help ofВ the brake system.

Turnaround test when reversing with help ofВ the brake system. While reversing around aВ ring, abruptly push the clutch and brake pedals toВ the end. Both front wheels must lock, rear loaded wheel must not lock. After pressing the pedals car should turn around.

Locking ofВ the front wheels when the brake pedal is pressed must occur for any level ofВ wheel loading. For example, when aВ car move inВ aВ drift, the body rolls, and some wheels are loaded, othersВ вЂ“ are unloaded. If the braking system is weak, front loaded wheel may not lock.

The test must be performed inВ clockwise and counter-clockwise move directions, since the braking system can work вЂњcriss-crossвЂќ, creating slightly different braking efforts for wheels on the same axle (depending on correct setting ofВ the braking system).

Practice shows, that turning around with help ofВ the brake system is not effective, if drift angle is close toВ 180В degrees or equal toВ 180В degrees (reverse moving). When pressing the brake pedal the front wheels lock, there is braking effort on the rear wheels, but car will not turn around. Therefore firstly it is necessary toВ deflect trajectory byВ turn the steer, after which already lock the front wheels with the service brake. InВ addition, drift angles inВ range ofВ approximately 90вЂ”140В degrees are also unsuitable for performing turnaround using the brake. While moving inВ drift at these angles rotation speeds ofВ wheels is low and their locking will not significantly change angle ofВ drift.

On aВ rear-wheel-drive car you can increase angle ofВ drift, if you cause the rear wheels toВ skid (gain engine speed inВ first or second gear and release the clutch pedal). On aВ front-wheel-drive car wheels skidding should reduce drift angle. On both front-wheel-drive and rear-wheel-drive vehicles the torque and inertia moment ofВ the engine should be enough toВ cause the drive wheels toВ skid. InВ addition, toВ create skidding ofВ driving wheels, anti-skid system (traction control) should not be installed onВ car.

The figure shows performing turnaround using the brake, when the car is moving inВ deep slide. InВ the chapter вЂњTurnaround while reversing (police turn)вЂќ, it was noted, that the success ofВ turnaround is affected byВ reverse steerability, namelyВ вЂ“ it should not be too low. The same requirement applies toВ performing turnaround with help ofВ the brake.

Requirements for successful return from an obtuse drift angle with help ofВ the brake system

вЂў when moving inВ an obtuse drift angle after pressing the brake pedal toВ 100%, the front wheels must lock, rear loaded wheel must maintain rotation;

вЂў drift angle should be high enough, but should not be close toВ 180В degrees (reverse moving), approximate angle rangeВ вЂ“ is from 140В toВ 160В degrees;

вЂў steerability ofВ reverse moving should not be tooВ low.

Let us try another experiment. When the car is inВ drift (angle ofВ about 150В degrees), turn the steer toВ stop inВ direction ofВ increasing drift angle. We will assume, the car is moving inВ neutral gear or with pressed clutch pedal, and the front wheels are inВ the вЂњstraightвЂќ position.

As we can see, after turning the steer the car began toВ slowly turn around. Trajectory was slightly curved. Tyre traces were interrupted, as the car moved almost inВ reverse for short distance. Steer turn allowed not only toВ turn around, but also toВ bend trajectory against the direction ofВ drift. We observed similar trajectory bending, when performing aВ police turn (trajectory bending was undesirable, we tried toВ eliminate it with help ofВ preliminary deviation).

Let us compare two ways ofВ return from drift with an obtuse angle: byВ locking the front wheels and turning the front wheels.

Left part ofВ the figure shows turnaround, made byВ locking the front wheels, and the right partВ вЂ“ shows turnaround, accomplished byВ turning the steering wheel (police turn). Turnaround ofВ the car with help ofВ the brake system is faster and trajectory is generally close toВ straight line. The second method, unlike the first, allows you toВ deflect trajectory inВ the direction, where rear part ofВ car looks when moving inВ drift (when the front wheels are locked, there is also deflection ofВ trajectory, but it is very small). Moreover the higher steerability when reversing, the faster turnaround will occur after turning the steer and the less curvature ofВ trajectory willВ be.

Aerodynamic elements, which increase side resistance toВ air movement ofВ rear part ofВ the body, can contribute toВ passive safety ofВ aВ car.

At the figure hatch marks the rear antiwing. When drifting occurs when moving at high speed, such aerodynamics on the rear ofВ aВ car can create an effort, which prevents increasing ofВ drift. Like tail ofВ an arrow, which stabilizes it inВ flight, aerodynamic elements on the rear ofВ aВ car prevent occurrence ofВ drift, but, at the same time, reduce steerability. And the higher speed ofВ movementВ вЂ“ the stronger effect. At low move speed and correspondingly low air flow rate the aerodynamics will not affect behavior ofВ the vehicle. Using such ofВ aerodynamics is justified: toВ pass high-speed corners it is not needful for high steerability, as angles ofВ corners are small, but for passing slower and sharp corners (for example, hairpins) need high steerability.

Notes on performing turnaround with help ofВ the brake system

вЂў if car has aВ powerful braking system, which can lock all wheels or road surface has aВ low grip on tyres (wet asphalt, snow-covered road), it is necessary toВ limit effort on the brake pedal, so as not toВ lock rear loaded wheel;

вЂў if car has already started toВ turn when performing turnaround, you may release the brake pedal;

вЂў when the front wheels are inВ locked condition, you should toВ straighten themВ вЂ“ so that car remains neutral behavior after releasing the brake pedal;

вЂў after drift angle becomes small (approximately 10вЂ”30В degrees), you may switch toВ tackle control byВ working the steer;

вЂў if machine has received aВ large moment ofВ rotation and drift angle increases rapidly, you should not wait for drift angle reaches 140вЂ”160В degrees and lock the front wheels toВ slow down the rotation; but after stopping the increase ofВ the drift, drift angle should hit into range ofВ approximately 140вЂ”160В degrees toВ complete turnaround.

Exercise 1. Provoke aВ drift with an amplitude ofВ more than 90В degrees on aВ front-wheel-drive car. Create skid ofВ the front wheels inВ the first or second gear toВ get out ofВ the drift.

Exercise 2. Provoke aВ drift with angle greater than 90В degrees on aВ rear-wheel-drive car. ToВ increase drift angle, cause the rear wheels toВ skid inВ the first or second gear.

Exercise 3. Provoke aВ slide angle ofВ 140вЂ”160В degrees. Return car, using the brake system toВ lock the front wheels. As soon as car starts toВ turn around, the brake pedal may be released.

Exercise 4. Provoke aВ sliding angle ofВ 140вЂ”160В degrees. Turn the steer inВ direction ofВ increasing drift toВ turn car around. Straighten the steer before completing turnaround.

Which ofВ the ways toВ get out ofВ drift, used inВ exercises 3В and 4, allowed you toВ perform turnaround faster?

Exercise 5. Accelerate car inВ reverse. Perform aВ small turn ofВ the steer toВ bend trajectory ofВ movement. Then perform turnaround byВ locking the front wheels.

Rocking, rhythmic drift

InВ the chapter вЂњDrift: causes ofВ origin and methods ofВ fightingвЂќ it was shown, that when passing an S-like corner drift can occur when moving toВ the second half ofВ the corner, which is related toВ the rocking ofВ car body. Let us understand, what causes occurrence ofВ drift and learn how toВ fight with rhythmic drift.

When passing aВ corner, centrifugal force causes the center ofВ mass ofВ car toВ move toВ the wheels, which are located on the outside ofВ aВ corner. Suspension springs ofВ the wheels, which are loaded with carвЂ™s mass, are compressed and store mechanical energy. When changing the direction ofВ corner the energy is released, the springs are discharged and push the center ofВ mass inВ the opposite direction, and other two springs begin toВ shrink. Definite frequency ofВ changing direction ofВ corners is able toВ increase amplitude ofВ movement ofВ the center ofВ mass. Resonant increase inВ movement ofВ the center ofВ mass ofВ machine is called rocking. Rocking can be longitudinal and transversal.

Longitudinal rocking

Longitudinal rockingВ вЂ“ is alternately moving the center ofВ mass along the direction ofВ car body (forward-backward) with increasing amplitude. During longitudinal rocking the front and rear suspension springs are alternately compressed and stretched.

Compressions and stretches ofВ suspension springs during driving can be caused byВ road roughness and resonant processes, which are related toВ characteristics ofВ suspension. InВ virtue ofВ loading ofВ the front and rear axles alternately changes, grip on the road ofВ the front and rear wheels changes sequentially. On the one hand, when the front axle is partially unloaded, grip ofВ the front wheels on the road worsen. For example, if the front axle bounces on aВ hillock inВ aВ corner, car will move almost straightforward during the front axle is inВ unloading state. On the other hand, unloading the rear axle can cause vehicle toВ drift. Unloading ofВ the rear axle is well felt, when aВ descent begins.

Longitudinal rocking is an undesirable effect, since

вЂў behavior ofВ machine becomes less predictable;

вЂў the best grip on the road is achieved, if load between the axles distributed evenly; longitudinal displacement ofВ the center ofВ mass redistribute load ofВ axles, the total tyre grip on the road is reduced;

вЂў efficiency ofВ acceleration and braking is reduced.

Longitudinal rocking can occur at small oscillation amplitudes and be invisible toВ aВ racer. When drive axle hits aВ hole, suspension contracts, and motor speed increases. When leaving aВ hole, suspension is released, motor speed decreases. ToВ change engine speed, it is needful toВ make an effort. The engine connected toВ transmission is able toВ partially absorb longitudinal rocking. Suppression ofВ longitudinal rockingВ вЂ“ is one ofВ the reasons not toВ disconnect the engine from transmission while driving.

Undesirable longitudinal vibrations on road roughness can be caused byВ incorrectly selected spring rates and resistances toВ bump and rebound ofВ shock absorbers. Often longitudinal rocking occurs on aВ car with weak shock absorbers and very strong springs: such aВ suspension does not вЂњswallowвЂќ roughness, but pushes away from them, while vibrations ofВ the body increase.

Bump resistance ofВ suspension is created byВ springs and shock absorbers. If aВ compressive force is applied toВ aВ suspension, aВ suspension movement, byВ which it is compressed, depends on springs. Shock absorbers are necessary toВ dampen compression-stretching vibrations ofВ springs and create additional resistance toВ the movement. How quickly bump or rebound occurs, mainly depends on shock absorbers.

When suspension springs are compressed, shock absorber rod moves inside shock absorber body, the shock absorber creates bump resistance. When shock absorber rod is pulled out ofВ the body, the shock absorber creates resistance toВ so-called rebound.

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