What is a Tandem Master Cylinder? 

A tandem master cylinder is a braking system used in automotive vehicles. In this system, a master cylinder is used to compress the nonhydrolic oil into hydraulic oil. In this article, I will discuss the topic “What is a tandem master cylinder”.


What is a Tandem Master Cylinder?

The tandem master cylinder is a crucial part of the hydraulic brake system, which is responsible for converting the force applied to the brake pedal into hydraulic pressure that ultimately slows down or stops the vehicle.

The term “tandem” in the context of a master cylinder refers to the arrangement of two separate hydraulic chambers within the cylinder. Each chamber is connected to a different brake circuit, usually dividing the braking system into front and rear circuits. The primary purpose of this design is to enhance safety. If one circuit fails (due to a leak or other issues), the other circuit can still operate, providing some level of braking functionality.

This type of master cylinder and brake line system assures greater safety, even if a pressure leak should occur in the brake line of one circuit, the other braking circuit works so that the vehicle provides a certain degree of braking.

In some cars, the front wheel brake system is of the disc brake type, and a drum-type brake(leading trailing shoes) is employed for the rear wheel brakes. The parking brake is mechanically operated by a wire and link system. It works on the rear wheels only. The same brake shoes are used for the parking and foot brakes.

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Working of Tandem Master Cylinder



Under normal conditions, depressing the brake pedal forces primary piston “A” towards the left, as shown in Fig. This movement pressurizes the oil immediately ahead for front left and rear right brakes. By this pressure and by the force of the return spring, secondary piston “B” moves similarly to pressurize the oil for the front right and rear left brakes.

In the event of the front left and rear right brake circuit failure, depressing the brake pedal causes primary piston “A” to move as above but, because the front left and rear right brake circuit cannot hold pressure, the oil immediately ahead of this piston does not get pressurized.


As piston “A” keeps moving to compress the spring, it begins to push piston “B” when the spring has been compressed fully, as shown in Fig. From this point onwards, piston “B” moves to pressurize the oil ahead and thus acute, the front right and piston “A” has little effect in pressuring its oil at first, because the initial rise in oil pressure causes piston “B” to promptly yield and move towards the left.

Very soon the forward end of piston “B” comes to and bears against the head of the cylinder. From this point onwards, the leftward movement of piston “A” becomes effective in pressurizing the oil ahead of it for front left and rear right brakes. The last pic shows the secondary piston “B” at a halt.

Tandem-Master-Cylinder-working (2)

In tandem master cylinder braking systems, even and rear splitting have also been used. In this system, one cylinder operates the front brakes while the other cylinder operates the rear brakes. However, there is a distinct advantage in the case of diagonal splitting. Here, if one circuit fails, the braking is halved and the braking stability is unaltered.

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Components of Tandem Master Cylinder


A tandem master cylinder consists of several key components that work together to convert mechanical force into hydraulic pressure for the operation of the vehicle’s brakes. Here are the main components:

1. Master Cylinder Body

The main housing contains various internal components. It usually has two separate chambers, each connected to a different brake circuit. This body helps to make contact of each of the components with each other.

2. Brake Fluid Reservoirs

Typically, there are two reservoirs attached to the master cylinder—one for each brake circuit. These reservoirs store brake fluid, which is essential for the hydraulic operation of the braking system. These brake fluid reservoirs need to be calibrated properly for the efficiency of the brake application.

3. Piston

Inside each chamber of the master cylinder, there is a piston connected to the brake pedal. When the brake pedal is depressed, the piston moves, creating hydraulic pressure in the brake fluid. This piston in the system is the one-way pressing machine and has the greater mechanical force to press the hydraulic oil. This piston is made of aluminum alloy makes it lightweight and strong.

4. Primary and Secondary Cups/Seals

These are rubber seals that prevent brake fluid from leaking between the piston and the cylinder walls. There is a primary cup on the side facing the brake fluid, and a secondary cup on the opposite side. The seals are used to stop the flow of the brake fluid, coming out of the system.

5. Pushrod

The pushrod connects the brake pedal to the piston inside the master cylinder. When the brake pedal is pressed, the pushrod transfers this force to the piston, initiating the hydraulic pressure. This push rod is responsible for the brake system to operate perfectly. The connection of the push rod and the piston needs to be precise and accurate so that it can operate without lag.

6. Check Valves

Check valves are used to maintain brake fluid pressure and prevent it from flowing back into the master cylinder when the brake pedal is released. This helps maintain responsiveness in the braking system. These valves are also responsible for way flow of the oil.

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Application of Tandem Master Cylinder

The tandem master cylinder has a wide range of applications in automotive vehicles. So, the application of these types of tandem master cylinder are-

  1. These types of master cylinders are commonly used in cars and other passenger vehicles.
  2. Larger vehicles, including trucks and commercial vehicles, often employ tandem master cylinders to handle the increased braking demands.
  3. Tandem master cylinders are frequently used in motorcycles equipped with dual disc brakes, where separate hydraulic circuits are dedicated to the front and rear brakes. This design enhances braking efficiency and safety for motorcycle riders.
  4. Tandem master cylinders are employed in off-road vehicles like ATVs (All-Terrain Vehicles) and dirt bikes.
  5. Tandem master cylinders find application in industrial vehicles, such as construction equipment and heavy machinery, where robust and reliable braking systems are essential for safety and productivity.

Advantages of Tandem Master Cylinder

The tandem master cylinder has several advantages like-

  • The tandem master cylinder has two separate chambers, each connected to a different brake circuit (typically front and rear brakes). This design provides redundancy, ensuring that if one circuit fails due to a leak or other issues, the other circuit remains functional. This enhances overall safety and reduces the risk of complete brake system failure.
  • The dual-chamber design allows for independent control of the front and rear brake circuits.
  • Tandem master cylinders are designed to provide a more responsive and consistent brake pedal feel
  • The dual-chamber design helps in dissipating heat more effectively. During heavy braking or prolonged use, brakes can generate significant heat.
  • This type of master cylinder is versatile and can be adapted to various types of vehicles, including cars, motorcycles, trucks, and industrial machinery.

Disadvantages of Tandem Master Cylinder

The disadvantages of these types of master cylinders are-

  • The complexity can make manufacturing, installation, and maintenance more intricate.
  • These types of master cylinders have higher manufacturing costs.
  • In some cases, if there is an imbalance in the front and rear braking systems or if one circuit is used more frequently, it may lead to uneven wear on the brake pads.
  • While the tandem design provides redundancy, there is still a risk that both circuits may fail simultaneously in certain scenarios, such as a catastrophic failure of the master cylinder.

Conclusion on What is a Tandem Master Cylinder

It’s important to note that modern vehicles often use anti-lock brake systems (ABS) in conjunction with tandem master cylinders to further enhance safety and control during braking events. ABS helps prevent wheel lockup and skidding during hard braking, especially in slippery conditions.

Frequently Asked Questions(FAQ’S)

What is the purpose of having dual circuits in a tandem master cylinder?

Dual circuits allow the braking system to be divided into two independent circuits, usually front and rear brakes. This design ensures that if one circuit fails, the other remains operational, providing a crucial safety feature.

How does a tandem master cylinder contribute to brake balance?

The dual-chamber design of a tandem master cylinder allows for independent control of the front and rear brake circuits, facilitating a balanced braking performance tailored to the vehicle’s weight distribution and braking requirements.

Is bleeding the brake system different for a tandem master cylinder?

Bleeding a brake system with a tandem master cylinder may be more involved, as it requires careful attention to both circuits to ensure proper removal of air bubbles. Following manufacturer-recommended bleeding procedures is crucial.

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