When we talk about the braking system of a commercial vehicle, we usually think of brake pads, discs or drums. But between the compressed air and the wheel there is a component that turns that pressure into mechanical force: the brake chamber.
If the brake chamber fails, the vehicle does not brake as it should or does not stay locked when parked, and that is a safety problem.
In this article we explain what a brake chamber is, which types exist, how to tell when it needs replacing and what to look for when choosing a replacement part. At the end we introduce the Industrias Onyarbi brake chambers we have in stock and ready for immediate delivery.
What is a brake chamber?
The brake chamber (also called brake cylinder or brake actuator) is the part of the air brake system that receives compressed air and turns it into the movement of a pushrod. That pushrod operates the lever or slack adjuster (on drum brakes) or the caliper (on disc brakes), and that is what brakes the wheel.
It is mounted on each axle, close to the wheel, and works in very harsh conditions:
That is why the brake chamber is one of the brake parts most often inspected and replaced on trucks, trailers and semi-trailers.
Types of brake chambers
Not all brake chambers are the same. These are the differences you need to know before ordering a replacement.
Single brake chamber (diaphragm or service chamber)
It has a single chamber with a rubber diaphragm. When the brake pedal is pressed, air enters, pushes the diaphragm and the pushrod extends. When the pedal is released, a return spring pulls the pushrod back.
It only works as a service brake, the brake used while driving.
Double brake chamber or spring brake
This is the most common type on axles with a parking brake. It has two chambers in one body:
Service chamber: works just like the single chamber.
Spring chamber: contains a very powerful spring. When the circuit is charged, the air keeps that spring compressed and the wheel turns freely. When the air is released, either because the parking brake is applied or because pressure is lost, the spring extends and brakes the vehicle on its own.
That is why the spring brake is also a safety device: if air is lost, the vehicle stays braked.
For disc brakes or for drum brakes
Disc brake chambers are mounted directly on the caliper and are usually more compact. Drum brake chambers act on the lever or slack adjuster and have a threaded pushrod with a clevis.
They are not interchangeable: the mounting, the pushrod length and the stroke are different.
Sizes: 16/24, 20/24, 24/24, 24/30, 30/30…
Brake chambers are identified by numbers such as 24/30. The first number is the size of the service chamber and the second is the size of the spring chamber. They indicate the effective diaphragm area in square inches: the higher the number, the more force the chamber delivers.
When replacing a chamber, always fit the same size specified by the axle or vehicle manufacturer.
How does it work within the braking system?
- Charging the circuit. The compressor fills the air tanks.
- Braking. When the driver brakes, the brake valve sends air to the service chamber.
- Actuation. The diaphragm pushes the pushrod, which operates the caliper or the brake cam.
- Release. When the brake is released, the air exits and the return spring retracts the pushrod.
- Parking. The spring chamber is exhausted and the spring brakes the wheel mechanically.
On vehicles with ABS or EBS, the modulator valves control the pressure reaching each chamber. If the chamber is not in good condition, those systems do not work as they should.
Symptoms of a faulty brake chamber
Any of these symptoms is a reason to have the brake chamber checked at the workshop.
How to choose a replacement brake chamber
- Type: single or double (spring brake).
- Application: disc brake or drum brake.
- Size: 16/24, 20/24, 24/30…, the same as the original.
- Pushrod and clevis: length and type, on drum brakes.
- Air ports and mounting studs: same position as the original part.
- Equivalent OEM reference: cross-referencing is the safest way to get it right.
Important for workshops: the spring inside the spring brake is highly compressed and stores a lot of energy. Never open the spring chamber. Before removing it, cage the spring with the release bolt, following the manufacturer’s instructions.
Industrias Onyarbi brake chambers: in stock and ready for immediate delivery
At Industrias Onyarbi we manufacture and sell spare parts for trucks, trailers and semi-trailers, and the braking system is one of our main product families. These brake chambers are currently available for immediate delivery:
They all share the advantages of our brake range:
If you run a workshop, a distributorship or a fleet, check availability and terms with our sales team. We will help you find the equivalent brake chamber from the original part number.
Frequently asked questions about brake chambers
What is the difference between a single and a double brake chamber?
A single chamber only works as a service brake. A double chamber, or spring brake, adds a spring that acts as a parking and emergency brake.
What does 24/30 mean on a brake chamber?
These are the sizes of the service chamber (24) and the spring chamber (30), in square inches of diaphragm area.
Can I fit a disc brake chamber on a drum brake?
No. The mounting, the pushrod and the stroke are different.
How often should a brake chamber be replaced?
There is no fixed interval. It is replaced when leaks, corrosion, excessive stroke or parking brake faults appear. It is advisable to check it at every service.
Reliable brake chambers, available today
The brake chamber is small compared with the rest of the system, but it determines whether the vehicle brakes properly on the road and stays immobilized when parked. At Industrias Onyarbi you will find brake chambers for trucks and trailers with OEM equivalence and immediate delivery.
