We know that disc brakes have better braking power. But why do heavy vehicles like trucks and buses still use drum brakes?
The answer, although disc brakes have many advantages, there are some things that only exist in drum brakes.
Drum brakes have wider friction contact than disc brakes. The wider the friction contact, the greater the load the vehicle can withstand.
So it can be concluded that the drum brake is stronger than the disc brake. Although drum brake is no more responsive than disc brake. In comparison, disc brakes will stop faster. However, the braking force of the drum brake is stronger.
That is the reason why the drum brake is chosen for the for heavy trucks.
Apart from this, there are several reasons why the drum brake is more suitable.
In fact, trucks can also use disc brakes. However, disc brakes for heavy trucks, should be designed with wide brake pads and thick rotors. Of course it will cost more.
Drum brakes offer a lower price so that the total cost of the trucks can be reduced.
2. Easy to combine with air brake
Disc brakes are suitable when combined with hydraulic brakes. However, heavy trucks generally use air brakes.
And it requires a complicated adjustment to combine disc brake with air brake system. However, the drum brake is easier to combine with the air brake.
The truck drum brakes, work like motorcycle drum brake. It has pivot to move both of brake shoes. And the pivot move by a lever. This lever, move by a vacuum chamber that connected to the air brake system.
That is why drum brakes are still the main choice for heavy trucks for front and rear brakes.
3. Easy maintenance
Rather than drum brakes on light vehicles, drum brakes on heavy trucks are of a very simple construction.
As a say in the point number 2, the construction is like motorcycle drum brake that are very simple.
It makes the maintenance process easy and doesn't cost too much.
4. Avoid accidents when braking
We know trucks with high loads can not to be stopped at close range. Even if the brakes can stop the trucks in short distance, there will be a weight transfer that causes the trucks roll and potentially crash.
So in trucks, how fast the brakes can stop the vehicle is not a priority. Most importantly, how the brakes can stop the vehicle safely.
This condition is suitable for drum brakes with a character that is not very responsive but strong with high loads.