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2025
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Why are disc brakes difficult to popularize on domestic trucks?
The use of disc or drum brakes on trucks is an age-old debate. Structurally, both disc brakes and drum brakes have their own advantages and disadvantages, but disc brakes have not developed nearly as much in the truck sector as they have in passenger cars. Compared to passenger vehicles, which now have disc brakes almost universally, domestic trucks—except for some imported European heavy trucks and hazardous material transport vehicles—rarely feature disc brakes. Let's analyze whether disc brakes should be used on heavy trucks based on the inherent characteristics of braking.
▎ Disc brakes have several important features compared to drum brakes:
1. Linear braking force. They are less likely to experience situations where light pressure does nothing but heavy pressure causes locking. The braking response is proportional to pedal input, making it smoother and easier to control.
2. Strong resistance to brake fade. In simple terms, this means the braking performance is not easily reduced due to overheating from continuous braking. The principle is easy to understand: disc brakes are directly exposed to the air, allowing heat to dissipate quickly, and the heat generated is easily carried away by the air. The widely used ventilated discs and drilled ventilated discs increase the surface area of the brake disc in contact with the air and the airflow speed, further highlighting this advantage of disc brakes.
3. Good braking force consistency. One very prominent advantage of good braking force consistency is that the vehicle is less likely to veer during braking or even lose control under extreme conditions. To use a simple analogy to describe the effect of poor braking force consistency:
Assume that on the same axle, the braking force on the left side is greater than that on the right. Differential gears have a characteristic where if the resistance on both wheels is equal, the driving force is also equal. If the resistance on the wheels is unequal, more driving force is transmitted to the wheel with less resistance. The greater the difference in resistance between the two wheels, the greater the difference in driving force. At this point, because the braking force on the right side is less than that on the left, the resistance is lower, so the right wheel receives more torque, causing the entire vehicle to tend to be pushed toward the left side.
Because disc brakes provide consistent braking force, it is easier to maintain vehicle stability when braking. I think this is also why the state mandates that the steering wheels of vehicles transporting hazardous materials must be equipped with disc brakes.
4. The drawbacks are also very obvious: high cost and significant wear. Because the contact area between the disc and the brake pad is small, they can easily experience insufficient braking force under heavy loads, making their adaptability to heavy loads inferior to drum brakes. However, the issues of high wear and poor heavy-load adaptability can already be technically addressed. After all, the performance advantages of disc brakes have been proven by their application on European trucks. The main obstacles to domestic promotion still lie in the high manufacturing costs and relatively high long-term usage costs.
But I believe that no amount of investment in safety is ever excessive. The sluggish domestic transportation market has made the development of costlier disc brakes difficult. Some opinions suggest that drum brakes are more durable and provide greater braking force, making them more suitable for heavy trucks. I think the performance of disc brakes on European heavy trucks has already proven their superiority. The reason drum brakes are still prevalent lies in cost; if automakers use disc brakes, the price goes up. With the freight market sluggish and operating costs high, truck drivers, who are already heavily burdened, naturally don't want to pay more. Therefore, it is inevitable that the development of disc brakes in China has stalled.
▎Editor's Note
Fundamentally, the driving force behind technological development and application is still financial investment. The sluggishness of the freight industry has directly caused difficulties in the application of many emerging technologies. For domestic trucks to reach world-class standards as soon as possible, it still depends on the steady development of the freight market and the support and improvement of national policies.
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