What is understeer and oversteer in a car What I want is the detailed principle, thank you

There are three types of drive for sedans: front-wheel drive (FF), front-rear-wheel drive (FR) and all-wheel drive (4WD). The so-called front-wheel drive refers to the drive form of front-mounted engine and front-wheel drive.

This is a form of drive that has only really emerged and been technically perfected after the 1970s, and most of the current small and medium-sized cars use this form of drive. The front-wheel drive integrates the transmission and the drive axle, which is fixed next to the engine and transmits power directly to the front-wheel drive vehicle.

Front-wheel drive refers to the drive form of front-mounted engine and rear-wheel drive. This is a traditional form of drive, and the Guangzhou Peugeot sedan, which Guangzhou people are familiar with, is a typical front-rear-wheel drive car. In this form of drive, the front wheels are responsible for the steering task, and the rear wheels are responsible for the driving work.

The power output by the engine is transmitted to the rear drive axle through the clutch, transmission, and propeller shaft, which drives the rear wheels to move the car forward, and in figurative terms, "pushes" the vehicle forward.

The four-wheel drive method was originally mainly used for off-road vehicles, but now it is also popularized in some cars, most notably some Subaru and Audi models. Four-wheel drive is further divided into four modes: full-time four-wheel drive (full-time), part-time four-wheel drive (part-time), real-time four-wheel drive (real-time) and part-time hybrid four-wheel drive.

For example, the Audi A43 0 and A6L4 2 use the qua tro is a full-time four-wheel drive; In general, off-road vehicles and SUVs are most commonly used to be four-wheel drive, which can switch between two-wheel drive and four-wheel drive through a joystick or button according to road conditions; Timely four-wheel drive is controlled by the computer, and it is two-wheel drive on the normal road surface, and becomes four-wheel drive when the abnormal road surface or the driving wheel is slipping; Timing Timing 4WD can be freely selected according to the driver's preference.

From the aspect of vehicle handling and safety, the center of the engine and drive shaft of the front-wheel drive car is in the front of the vehicle, and the driving wheel is also in the two front wheels, so when cornering, the center of gravity of the front part is forward due to inertia, and it is easy to break through the ground adhesion of the front wheels, resulting in understeer, commonly known as "pushing the head". The rear-wheel drive car is more average than the front-wheel drive car in the center of the vehicle, and it can generally reach the optimal ratio of 50 50, and the limit value of cornering is higher, however, because the front wheel of the car is directly dominated by the steering system has changed the direction of travel, and the driving wheel behind still has the inertia to move forward, so it is easy to oversteer, commonly known as "tail flicking". Four-wheel drive is a more balanced drive that avoids understeer and oversteer, but because the engine torque is distributed to the front and rear wheels, some power is sacrificed and it is more fuel-intensive.

The general car is three laps on the left and three laps on the right, but the position of the pull rod in the direction of some cars is misaligned, resulting in more than three laps on one side, and the steering angle exceeds the normal value, which is oversteering; If the other side is less than three turns, and the steering angle is less than the specified value, it is understeer.

Understeer is also called pushing.

Oversteer is also called tail flicking, which is drifting.

Understeer refers to a steering angle that is smaller than that of the front wheels when cornering due to insufficient friction on the front wheels.

Oversteer, which refers to the outward sliding of the rear wheels due to insufficient friction of the rear wheels

The reason for the lack of steering is that the deflection angle between the front wheels and the ground is established faster than the deflection angle between the rear wheels and the ground.

2.The factors that lead to understeer are as follows:1

Uneven weight distribution: Balanced weight distribution 50336050. If the front body mass is greater than the rear body mass (with a mass distribution of 50336050, such as 60336040), the car will suffer from understeer.

Conversely, if the front body mass is less than the rear body mass distribution 50336050 (e.g., 40336060), the vehicle will oversteer; The stiffness of the front suspension, including spring rate, shock absorber stiffness and anti-roll bar stiffness, is too high; The rear suspension stiffness (including spring rate, shock absorber stiffness and anti-roll bar stiffness) is too low; The center of the front roller is too high relative to the rear side; And the center of the rear tilt is too low for the center of the front tilt.

Oversteer is the need for a vehicle to reduce the angle of the steering wheels to maintain the desired path of travel. The torsion angle of the car body is greater than the angle of the steering wheel; Understeer is the result of the vehicle needing more steering wheel angles to maintain the desired travel lane, and understeer is caused by a greater velocity-slip rate at which the front tyre meets the ground than the rear-tyre.

Understeer and oversteer are important criteria for measuring the balance of vehicle handling, and in simple terms, understeer is the phenomenon when the front wheels of a car do not follow the direction of the steering wheel, but continue to move forward in a straight line. If the driver doesn't expect the car to react like this, it can be a scary experience. Although understeer is more common in front-wheel drive vehicles, it can still cause understeer if the driver is not careful when driving a rear-wheel drive vehicle.

When entering a corner, if the speed is too fast for the front axle to cope with the curve of the corner, the grip of the front wheels will fail sooner than the rear wheels. At this point, the car will slide straight forward without turning. In addition, if you brake hard to lock the front wheels when cornering, the car will also suffer from understeer, unable to turn and go straight ahead.

How does oversteer happen? When the rear wheels of the car lose grip while the grip of the front wheels is still valid, the rear end of the car will spin out of control and then flick its tail, allowing the car to enter a state of rotation. Generally speaking, rear-wheel drive vehicles are more prone to oversteer, as the driving wheels are more likely to slip and exceed the critical point of losing grip.

Oversteer can be more frightening than understeer for inexperienced drivers, especially if the rear of the car starts to skid. Lucky friend, the car will make a 360-degree rotation and stop when oversteering; Unfortunately, the car may skid and crash into other vehicles or objects. There are two factors that contribute to oversteer: worn tires and high-powered rear-wheel drive models.

Once the tires of a car are worn to a certain extent, their grip on the road is relatively weak, and it is easy to slip when cornering, causing oversteer. A high-performance rear-wheel drive car that accelerates when cornering can also cause the rear wheels to oversteer beyond the critical point of grip. (Photo by photo:.)

Yalan Chen) @2019

What to do with oversteer and understeer:

1. Understeer is commonly known as "pushing head", which is manifested as the actual steering angle of the vehicle in the bend is smaller than the rotation angle of the front wheels, that is, the front wheels have slid outward, in more popular terms, the turn is more acute than the actual turn of the car. The consequences of understeer can be as low as sliding the car into the opposite lane, or as severe as sliding off the road and causing an impact.

2. Oversteer is generally the opposite of understeer, oversteer is commonly known as "tail flicking", which is manifested as the actual steering angle of the vehicle in the bend is larger than the rotation angle of the front wheel, that is, the rear wheel has slid outward, and the same is explained in popular language that the turn is not as sharp as the car is actually turning. When oversteering, the vehicle can easily spin or even slide off the road surface and collide;

3. Due to the characteristics of the vehicle, the front-wheel drive models are often more likely to have "understeer", and the rear-wheel drive models are often more prone to "oversteer", but this situation is not absolute, and the rear-wheel drive models will also have "understeer", and it is not uncommon for front-wheel drive models to have "oversteer". Let's analyze the specific causes of "understeer" and "oversteer".

1.Steering is a common phenomenon in front-wheel drive vehicles, and oversteer is a common phenomenon in rear-wheel drive vehicles. Our family cars are more inclined to turn.

2.Turning, commonly known as pushing the head, is the phenomenon of the front of the car turning into the curve and sliding to the outside of the curve. Front-wheel drive vehicles with engine front steering.

3.Front-engined vehicles are relatively heavy, and inertia can lead to cornering phenomena when cornering quickly.

4.Rear-wheel drive vehicles can oversteer. Oversteer is dangerous. When the vehicle makes a quick turn, the vehicle follows the required trajectory but slides to the inside of the curve. Cars that are prone to oversteer are very prone to losing control when cornering quickly, and the driving technique is very dangerous.

5.If the weight ratio of the front and rear of the car is relatively balanced, then the car will oversteer. The front-to-rear weight ratio of many sports cars is the same, such as BMW, Cadillac ATS, Alfa Romeo Ju, etc.

6.Family cars are prone to turning. After turning, the driver can correct the curved trajectory by slowing down and correcting the direction, making it safer.