When it comes to vehicle brakes, there are two main designs: drum brakes and disc brakes. Previously, we have mentioned how the difference in various forces causes your front car brake systems - as well as car tyres - to wear out quickly. Here, however, we will look at the differences in these brake types.
Normally, drum brakes are featured in trucks and other larger goods vehicles. However, while it is true that many cars favour disc brakes, they often utilise a mixed or dual braking system - disc brakes in the front and drum brakes in the back. As such, even if you don’t own a lorry or industrial vehicle, it’s worth knowing about the two different types of brakes.
Lorries and HGVs often use more drum brakes when compared to standard vehicles.
How do disc brakes work
As the name suggests, a central component to these brakes is a large spinning disc. When the brakes are applied, calipers push the brake pads against the disc, clamping down. It is this friction that then brings the vehicle to a halt. This effect is similar to the braking system seen on common bicycles.
Benefits of disc brakes
One of the key advantages to using disc brakes is that they are more effective in the heat. This is because the disc expands and is closer to the pads, even when the calipers and clamps are relaxed. As such, you don’t need to force the pedal so much to make a connection and brake.
An example of a disc brake installed behind the car tyre and wheel
Likewise disc brakes are less likely to warp, offer a better stopping power and can cool down quicker than drum brakes. This helps them avoid brake fade, where high temperatures can permanently decrease the stopping power of your brakes thanks to reduced friction.
Similarly, these brakes are also highly useful in wet conditions. The water washes off of the disc, rather than building up and preventing friction. They are also more affordable, since individual rotors or discs can be replaced, rather than having to replace entire components.
Drawbacks of disc brakes
As a disadvantage, disc brakes require more hydraulic pressure than drum brakes. They also usually require an Anti-locking (or Anti-skidding) Braking System, or ABS for short, adding to the costs. This ensures that, while effective, disc brakes are more expensive to produce, despite being easier to maintain in the long run.
Furthermore, because they are external, rather than self-contained like a drum brake, these discs tend to generate a large amount of external noise. Of course, tyre noise is also generated based on your choice of tyre, but the brakes cannot be completely silent when braking by their very nature.
How do drum brakes work
Drum brakes are named after the large drum that contains the braking system itself. Inside, there are a pair of curved brake pads. When the brake pedal is applied, a slave cylinder pushes both of these brake pads out, rubbing against the inside of the drum to generate friction.
Advantages of drum brakes
Drum brakes are simple from a design point of view and can operate via their own hydraulic actuators and mechanical design. As a result, they don’t require the ABS brakes or assistance that disc brakes do.
It’s also worth noting that drum brakes don’t require extra power and can help multiply a braking force, thanks to the large brake pads and friction generated. This is also servo effect allows the drum to easily lock the wheels.
Drum brakes can not easily expel water, leading to rust and other defects.
Likewise, drum brakes have the opposite effect in hot temperatures when compared to disc brakes. While the disc expands closer to the pads, the drum expands further away from the pads, requiring more pressure and pedal power to achieve the desired amount of braking. The hotter it gets, the harder it is to brake.
Although drum brakes to contain springs to help reset the position of the pads, the braking force is slower to disperse compared to disc brakes. This is due to the servo effect of the brakes, making them less suitable for high precision driving.
Why vehicles use both
It’s clear that both disc and drum brakes have their share of advantages and disadvantages, so it should come as no surprise that vehicle designers choose to use both in their car designs. That being said, why are the front axle brakes nearly always of the disc variety?
As we’ve previously discussed, bringing a car to a full stop requires generates a lot of inertia and momentum. Regardless of how the weight is distributed in your car, braking will cause this pressure to shift forward onto the front car tyres and brakes. Because disc variants are more versatile, handling larger amounts of heat, as well as water and other damage, they are more reliable in the front. Drum brakes, on the other hand, are useful in the rear where they can lock the wheel and apply greater force.
Having car tyres suited to your driving environment will also help with braking.
Similarly, because disc brakes work primarily through hydraulics, they’re not ideal at keeping the car from moving via the likes of gravity. This makes drum brakes better for hand braking.
Of course, it’s also worth mentioning that the type of car tyre you use is also vital. Winter tyres, for instance, often focus on offering better grip, thanks to a thick tread and directional tyre pattern.
Influence on tyres
Tyres will gain wear and tear over time as a result of being used, as well as your choice of steering system, car suspension and camber angle, but the amount of braking you do is also changes this.
As mentioned previously, braking shifts the distribution of weight to the front, where it pushes down on the front brakes (usually disc brakes) and tyres. As a result, a well maintained tyre pressure will also be useful during this process.
You should also remember that slowing the car down naturally - as much as is safe to do so - will help ease up on the wear and tear sustained by both your brakes and car tyres. Not only does this prevent unnecessary damage, it is also a useful way of improving your fuel economy.