front-wheel drive car-tail-flick
rear-wheel drive car-push the head
four-wheel drive car-swing together!
The first snow in 2020 comes earlier than ever before, and the end of the year is the peak season for car sales. In order to no longer squeeze the "second road car on the eighth floor", many consumers can't restrain their desire to buy a car.
However, every snowy day is a stage where the traffic accident rate is soaring. The maintenance plant is basically "full of cars"; the reason is that a large number of novices generally do not have the driving experience on snow and ice, even after the snow melts. It is also difficult to control vehicles safely in the stagnant water section. You must know why the road after the rain is called "slippy road"! ——The reason is that the friction coefficient of the tires will drop by 30%-40%, and the braking distance will be prolonged proportionally. Therefore, the safety distance has to be enlarged a lot. What about ice and snow?
basic driving precautions
highway driving after snow is relatively simple, because the snow is still in a relatively soft state, the first batch of vehicles to enter the snow need to pay attention to only the starting and "speed" (turning speed) control. If the snowy road at the start is still soft, the forward gear can be controlled in the second gear and the accelerator can be controlled; manual transmission vehicles can be semi-linked for a relatively long time, and automatic transmission vehicles only need to be controlled after upshifting through M gear (manual mode) Starting speed. When starting with a small number of forward gears, the "wheel torque" will be greatly amplified. If the speed is high, the torque will easily be greater than the coefficient of friction between the tires and the snowy road, resulting in wheel slip. Therefore, the fueling valve must be slow. The slower the vehicle starts, the more stable it will be; the third gear is recommended for starting on ice, because the larger the number of forward gears, the lower the torque of the wheel at the same speed, and the friction coefficient on the ice surface Only one-tenth of conventional roads!
Key point: The braking distance on icy and snowy roads should be extended several times! The reason should not be repeated. The braking distance should be increased as much as the friction coefficient decreases; therefore, when driving and decelerating on snow and ice, the distance from the vehicle in front should be at least about 100 meters, and the speed should be controlled within 20km/h.
What you need to pay attention to is the strength and method of braking. Regardless of snow or ice, the brake pedal must not be stepped too heavily, otherwise the wheels will lock easily; even if the ABS system can prevent locks, it will lock on ice. The body slips at the moment of death. Therefore, the braking deceleration must be slow, which is why it is recommended that the safety distance between vehicles be large enough.
try not to use the "engine braking" method at the same time. When a manual transmission car is downshifted and decelerates, there will be a frustration, and the body posture may deviate due to the frustration; when an automatic transmission car decelerates to a low speed, it should [engage N gear], That is, the neutral gear is used to reduce the speed by braking. The reason for
is the deceleration process of D gear, which is the interaction between the brake and the brake disc torque. Even if the brakes are stopped, the actual wheels are still driving the brake disc output torque; therefore, it is difficult to stop when braking on the ice surface of D gear. After removing the neutral gear and cutting off the power output of the engine, it can not skid when it is about to stop. If there are doubts about this kind of operation, you can choose the ice surface of the clear channel for testing.
Safe driving · Necessary configuration
snow chain is the most important configuration!
No matter whether the car is front-wheel drive, rear-wheel drive or four-wheel drive, without snow chains, it can only do the "make-up driving" described in the first section. The difference is nothing more than stability at the start, but it is easy to slip when turning.
1: The three major front-wheel drive cars are concentrated in the front of the car, and the front wheel grip of the car is much greater than the rear wheel; therefore, it is easy to see that the front wheel can be guided normally when turning, but if the speed is faster, the rear will "flick" . If you want to make a safe turn, you must strictly control the speed of the turn. However, braking on ice is difficult. Such an operation will inevitably increase the driving risk factor. The solution of
is to install snow chains on the front and rear wheels, iron snow chains are mainly used on snow, and snow chains with TPE material and ice-breaking nails are mainly used on ice.
2: Rear-wheel drive cars have the same grip on the front wheels, and the kerb quality is often greater than that of the same-level front-wheel-drive cars. The theoretical driving stability should be higher; but ordinary passenger cars that can use the rear-drive system, such as cars and MPVs They are generally performance cars ≥2.0T. The power reserve of this car determines that the output power of the 2/3 gear will be high, that is, the torque of the rear wheels will always be large, soThe vehicle is prone to skidding when starting, and the torque of the rear wheels is greater than the friction of the front wheels when turning-the front wheels lose their guiding function and the body will be pushed straight.
So rear-wheel drive cars are easy to push the head, but the so-called push head and front-wheel drive understeer are not the same concept. The reason why the push head goes straight is only because the power is too strong; and the rear-drive vehicle's tail flick is also because the output power is greater than the friction. , Causing the wheels to spin at a high speed, causing the wheels to appear centrifugal force to pull the body to slip. Therefore, rear-wheel drive vehicles also need to install snow chains on the front and rear wheels, otherwise poor driving skills will be more difficult to control than front-wheel drive vehicles.
3: Four-wheel drive vehicles also need snow chains! Because the front and rear wheels can output power, this is two problems with that the friction coefficient of each wheel on the ice is only 0.1; no matter how many wheels are driven, the wheels will slip and stability at the start?
and the front and rear wheels of four-wheel drive vehicles will produce centrifugal force when turning. A slight error in the throttle control will cause the entire vehicle to "translate"; then the tire chains are indispensable for stable driving. ! ——This kind of system cannot use four-wheel drive on the road with excessive friction, because the electronic control system will force the four wheels to drive at the same speed, but the speed of the four wheels is completely different when the car turns; if you use anti-skid If the chain is forced to use a four-wheel drive, the rear wheel will push the front wheel to walk in a straight line when turning, and the snow chain on the front wheel is likely to "scrub off".
Summary: These are the precautions for driving on ice, in short, it is a jingle.
start slowly
slow down
safe distance
icy road is best not to drive, if you have to drive, you must prepare snow chains, otherwise you may have to wait in line to repair the car.
This article comes from the author of Autohome and does not represent the viewpoint of Autohome.
