In 1917, a mechanic invented a new type of brake that was hydraulically operated. A couple of years later he improved his design and introduced the first modern hydraulic brake system. Although it was not completely reliable due to problems with the manufacturing process, it was adopted in the automotive industry with some changes. That man’s name was Malcolm Loughhead and, in addition, the disc brakewould also become one of the founders of Lockheed Corporation.
Today, due to advances in materials and improved manufacturing, disc brakes are much more effective and reliable. Most modern vehicles have four-wheel brakes, operated by a hydraulic system. These can be disc or drum, but since the front where the brakes play a more important role, rare is the car that does not have a set of discs at the front. Because? Because during a stop, all the weight of the car falls forward and, therefore, on the front wheels.
Parts of a disc brake
Like most parts that make up a car, a braking system is a mechanism made of multiple components for the whole to function properly.
The main ones in a disc brake are:
- Tablets: They are located inside the caliper on both sides of the disc so that they can slide laterally, towards and away from the disc. A brake pad consists of a pad of friction material molded to a metal backing plate. On many brake pads, noise-reducing shims are attached to the plate. If any of them are worn or near that limit, or have any damage, all axle pads should be replaced.
- Tweezers: Inside it contains the piston that presses the pads. There are two: fixed and floating. The former are often installed in sports cars and luxury cars. Most vehicles on the road today have floating brake calipers, and almost all have one or two pistons on the inner side. Compacts and SUVs typically have single-piston calipers, while larger SUVs and trucks have dual-piston calipers in front and single-piston calipers in the rear.
- Discs: They are mounted on the hub and rotate integrally with the wheel. During braking, the vehicle’s kinetic energy is converted into heat due to friction between the pads and the disc. To better dissipate, most vehicles have ventilated discs on the front wheels. The rear discs are also made ventilated on the heavier ones, while the smaller ones have solid (non-ventilated) discs.
Regarding the material, due to the high temperatures that disc brakes can reach, are often made of molten iron due to the materials’ ability to withstand extreme heat, ease of manufacturing and low production cost. That said, some brake discs are made from carbon-based compounds, ceramics, and alloys, but they tend to be more expensive. These types of systems are only reserved for high-performance vehicles, where effective stopping at very high speeds must be guaranteed.
Types of brake discs
Once the basics of brake disc systems are understood, it is interesting to summarize in points what types of brake discs we find in cars since, the higher the range, the larger and better brake discs we will find in the vehicles we see on the street. In this list we will gradually relate the virtues and characteristics of the simplest discs to the carbon-ceramic discs that we can find in the highest ranges of premium cars on the market.
Conventional brake discs
- Material: Cast steel.
- Use: Suitable for most vehicles for daily use.
- Characteristics: Durable and affordable, they provide efficient braking under normal driving conditions.
slotted discs
- Material: Cast steel.
- Use: Improved performance in intensive driving conditions.
- Characteristics: The grooves help evacuate the heat and gases generated during braking, thus improving efficiency and reducing the risk of slipping.
perforated discs
- Material: Cast steel.
- Use: Improved cooling and performance in more demanding driving conditions.
- Characteristics: The holes allow greater heat dissipation, prevent the accumulation of gases and water on the braking surface, thus improving braking effectiveness.
Composite discs
- Material: Combination of steel and composite materials.
- Use: Improved performance in sports vehicles.
- Characteristics: The combination of materials provides greater heat resistance and reduces the weight of the assembly, improving braking capacity and response.
Carbon ceramic discs
- Use: High performance and competition applications.
- Features: Extremely light, they offer excellent resistance to heat and wear. Ideal for high-performance cars such as the Alfa Romeo Giulia QV or the Porsche Taycan as they reduce unsprung weight, improve brake response and provide greater durability in driving moments more adapted to the circuit than to the road.
How do disc brakes work?
Disc brakes are similar to bicycle brakes. When pressure is applied to the lever, it pulls on a metal string that presses two shoes against the rim of the bike’s tire, causing friction with the rubber pads. Similarly, in a car, when pressure is applied to the brake pedal, this forces fluids circulating through pistons and tubes to squeeze the brake pads. In a disc brake, the pads squeeze the disc rather than the wheel, and the force is transmitted hydraulically rather than through a cable.
The friction between the pads and the disc slows down the vehicle, causing the disc to become very hot. Most modern cars have disc brakes on both axles, although in some models with limited motorization or with a few years behind them, the disc brakes are maintained. drum brakes behind. Either way, the harder the driver presses the pedal, the greater the pressure inside the brake lines and the harder the pads will squeeze the disc. The distance that the pads have to travel is small, only a few millimeters.
Do disc brakes need maintenance?
As a result of friction, brake pads need maintenance or else problems may appear such as squealing or creaking and braking power that should not be optimal. If the problems are not resolved, it may lead to a failed technical inspection (ITV). The most common type of service required for disc brakes is little more than changing the pads.
These generally have a metal piece called wear indicator. When the friction material is on its last legs, the indicator will contact the disc and make a squeaking noise. This means it’s time for new brake pads. Checking for wear will require some tools and time, as well as ensuring that the wheel bolts are torqued correctly. For some it may be too much, so if you want to save time, it is best to go to a trusted workshop.
How often should disc brakes be changed?
Even in normal driving situations, disc brakes endure a lot of stress and, over time, certain components will need to be replaced. The pads need to be replaced more frequently, although when is undetermined.
That depends on your particular driving habits, as well as the material they are made of, but it varies. between 40,000 and 120,000 kilometers. Discs usually last between 80,000 and 120,000 km (and sometimes longer), while the calipers and pistons should last the entire life of the vehicle.
Advantages and disadvantages of disc brakes
Advantages:
- They are lighter than drum brakes.
- They have better cooling (the braking surface is directly exposed to the air).
- They offer better resistance to fading.
- They provide uniform pressure distribution.
- Replacing brake pads is a relatively simple task.
- By design, they are self-adjusting brakes.
Disadvantages:
- They are more expensive than drum brakes.
- Greater pedal pressure is required to stop the vehicle (which is why a brake booster is necessary).
(NOTE: Article originally published on 10/24/2020, corrected and expanded)
