Truck Braking Systems Explained

How does a braking system on a lorry work?

Unlike passenger cars, lorries mainly use an air braking system. This system uses compressed air to transmit braking force to the vehicle’s various axles and any trailer or semi-trailer.

The air is produced by a compressor and stored in air reservoirs. When the driver presses the brake pedal, this air pressure is directed via valves and pipes to the brake components. This generates sufficient force to bring a vehicle weighing tens of tonnes to a controlled stop.

Modern lorries are also equipped with electronic assistance systems such as ABS ( Anti-lock Braking System ) and EBS ( Electronic Braking System ). These systems ensure that braking force is distributed optimally and that the driver retains maximum control, even during emergency stops or in poor weather conditions.

The key components of a lorry braking system

A modern braking system consists of a large number of components that must work together perfectly. If a single component fails to function properly, this can affect the performance of the entire system.

ABS sensors and pulse rings

ABS sensors continuously measure the rotational speed of the wheels. If a wheel is in danger of locking up during braking, the system intervenes immediately. This ensures the lorry remains controllable and optimises the braking distance.

Faulty sensors or damaged pulse rings can lead to error messages on the dashboard, reduced braking performance and failure to pass roadworthiness tests.

EBS valves and pressure sensors

The Electronic Braking System (EBS) forms the electronic brain of modern braking systems. EBS valves and pressure sensors process information from various sensors and ensure that the correct braking pressure is applied to each wheel.

Particularly in recent MAN, Volvo, Renault and Mercedes-Benz models, these components play a crucial role in the vehicle’s safety and efficiency.

Air dryers and air receivers

Air forms the basis of every air brake system. However, moisture in compressed air can cause serious problems, such as corrosion, freezing or damage to valves.

That is why the air is first passed through an air dryer before being stored in the pneumatic cylinder. A faulty air dryer is often underestimated, but can eventually lead to costly damage to various parts of the braking system.

Pipes and quick-release couplings

The compressed air must circulate safely and efficiently throughout the entire vehicle. Various pipes , couplings and connections are used for this purpose.

Even a small air leak can cause a loss of pressure, slower braking responses and increased strain on the compressor. Regular inspection of pipes and quick-release couplings is therefore essential.

Brake pads, brake linings and brake discs

In disc brakes, brake pads apply pressure to the brake disc. The resulting friction causes the vehicle to slow down.

Brake pads and brake discs are among the most common wear parts on a lorry. Timely replacement prevents damage to other components and ensures optimum braking performance.

Brake drums and brake shoes

Although disc brakes are becoming increasingly common, drum brakes are still used on certain axles and vehicles.

In this system, brake shoes press against the inside of a brake drum to slow the vehicle down. Proper maintenance remains important to prevent uneven wear and reduced braking power.

Brake calipers, brake cylinders and spring-loaded brake cylinders

Brake calipers convert air pressure into mechanical braking force. If a brake caliper becomes stuck, this can lead to excessive wear, overheating and uneven braking behaviour.

Brake cylinders and spring-loaded brake cylinders also play a crucial role. Spring-loaded brake cylinders, in particular, are important for the parking brake function and the safety of stationary vehicles.

Brake regulators

Brake regulatr ensure that braking force is distributed correctly depending on the vehicle’s load. This not only increases safety but also helps to minimise wear on brake components.

Common brake problems in lorries

Even the most reliable lorries will, sooner or later, experience wear and tear or faults in the braking system. By identifying problems at an early stage, serious damage and costly repairs can often be avoided.

Warning lights on the dashboard

ABS or EBS warnings must never be ignored . They often indicate faulty sensors, damaged wiring or problems with electronic components.

Slow pressure build-up

If it takes longer than usual for the air pressure to reach the required level, this may indicate a faulty air dryer, leaking pipes, a worn-out compressor or problems with the air receivers.

Air loss

Hissing noises or a rapid drop in air pressure are clear signs of a leak in the system. Small leaks can quickly develop into bigger problems.

Uneven braking

Does the lorry pull to one side when braking? This may be due to worn brake pads, faulty brake calipers or problems with brake force distribution.

Excessive wear

If brake pads, brake discs or brake shoes are wearing out faster than normal, it is important to investigate the underlying cause. Often, the cause lies with a faulty brake caliper, incorrect adjustment or a problem in the air system.

Why preventive maintenance is so important

For transport companies, downtime means a direct loss of time and money. A faulty braking system can also lead to safety risks, failure to pass roadworthiness tests and unexpected repair costs.

Preventive maintenance offers several benefits:

• Improved road safety

• Reduced risk of unexpected downtime

• Longer service life of components

• Lower long-term maintenance costs

• Better vehicle performance

• Greater reliability for drivers and transport companies

By regularly inspecting brake components and replacing them in good time, many problems can be prevented before they have serious consequences.

Conclusion

A lorry’s braking system is a complex interplay of mechanical, pneumatic and electronic components. Parts such as ABS sensors, EBS valves, air dryers, air reservoirs, brake pads, brake discs, brake calipers and spring-loaded brake cylinders all contribute to the safe and reliable operation of the vehicle.

Whether it’s a MAN, Volvo, Renault Trucks or Mercedes-Benz, regular maintenance and high-quality parts remain essential to guarantee maximum safety, performance and operational reliability. By identifying wear and tear in good time and taking preventative action, hauliers and workshops can significantly reduce costly faults and unwanted downtime.

Are you looking for the right brake parts for your lorry, or would you like technical advice from our specialists? Our team will be happy to help you find the right solution for your vehicle or fleet.

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