Why do the front brake pads wear faster than the rear wheels?
Older drivers who drive more miles know that the front wheel brake pads, brake discs, tire wear are faster than the rear wheel, and the brake pads and discs are larger than the rear wheel, what is the reason? Let's illustrate this with a front drive
Whether the car is driving forward or braking, the final rely on the friction with the ground, if there is no friction with the ground, either can not go, or can not stop. Let's look at the brake first, when we step on the brake pedal, through the brake oil to transfer the brake force to the brake pump, the brake pump to push the brake pad to hold the brake disc, the disc and the disc friction to produce brake force, do not let the wheel rotate, and then the wheel through the friction with the ground, to achieve the role of the brake.
Therefore, the greater the friction between the tire and the ground, the greater the friction between the brake pad and the disc, the better the braking effect. Because the brake pads and discs are the first threshold of braking force, they must generate enough friction to brake force. If the brake pads are of the same material, the braking force can only be increased by increasing their contact area.
Therefore, the larger the brake pad, the greater the braking force, because when braking, the role of the front wheel is much larger than the rear wheel, so the front wheel needs greater braking force. The car is moving forward, and when it brakes, the car will continue to move forward because of inertia. The inertia force moving forward is not in the same straight line as the friction force behind the wheel, the inertia force moving forward in the center of gravity of the car, the friction force moving backward on the ground, at this time the inertial force is greater than the friction force and the height is high, under the action of these two forces, a forward rolling torque is formed, so that the head of the car is pressed down, the tail is tilted upward, and there is a forward rolling trend. In this way, the pressure of the front wheels of the car on the ground increases, and the pressure of the rear wheels on the ground decreases, plus the weight of the front of the car is large, and the pressure of the front wheels is also large. And because the friction is proportional to the pressure between the two objects, the braking force generated by the front wheel is larger than the braking force of the rear wheel, so the brake pads are larger than the rear wheel, and the wear is faster than the rear wheel, generally changing the front brake pads twice to change the rear brake pads once
Some models will also make the front wheel is the disc brake, the rear wheel is the drum brake, many people think that the drum brake heat dissipation is poor, unreliable, do not want to buy such a car, or want to change the disc brake after buying. In fact, there is no need at all, because the rear wheel brake force is not large when braking, if it is not often a long downhill section, it will not produce brake overheating. Even if you often walk a long downhill section, hang to a reasonable gear, and cooperate with the engine brake, the brake does not need to step on a lot.
Finally, look at the tires, the front wheel brake force, tire wear is also large. The most important thing is that the front wheel as a driving wheel, driving time with the ground has greater friction, the rear wheel is from the driving wheel, only need to follow the rolling, the friction is very small. Therefore, the front tire is more serious than the rear tire wear, and often do a four-wheel transposition, which helps the four tires wear evenly, and generally 20,000 kilometers need to transposition once.
