The brake caliper is an important component of any modern brake system with disc brakes. However, the component, also known as the brake caliper or fist caliper, can wear out or break over time. In this guide, you will learn how defective brake calipers can be noticed and what the possible causes are. You will also receive valuable tips on how to replace the brake caliper in your car.

Function of the brake caliper in the car

As part of the braking system, the brake caliper ensures that the brake pads are pressed onto the brake disc precisely and with high pressure. The caliper guides the brake pads and accommodates the brake piston. The caliper itself is connected to the brake caliper carrier via guide pins and is mounted so that it can be moved.

Brake caliper transmits force during the braking process

When the driver depresses the brake pedal, this force is converted into brake pressure by the brake master cylinder. This pressure is transmitted to the brakes via the brake lines by means of brake fluid. Here, the brake piston displaces the movable brake caliper of the respective brake. The brake calipers thus press the brake pads firmly against the brake discs. When the brake pedal is released, the pressure in the brake system drops. Guided by the guide pins, the brake calipers move back to their original position. Depending on the brake system, the parking brake also acts on the rear brake discs via the brake calipers. A small motor for the function of the electric parking brake is often integrated in the brake caliper.

Causes of a defect in the brake caliper

Brake calipers are robustly constructed and are considered durable. However, in the suspension area, they are exposed to stresses from dirt, moisture and road salt. This can lead to wear and rust on the brake caliper, which is often the cause of defects that occur. A sporty driving style or the effects of an accident also occasionally lead to damage to the brake calipers.

Common reasons for defective brake calipers:

• Rust due to weather influences
• Wear due to a sporty driving style
• Damage due to an accident
• Mistakes during repair
• Cracks due to thermal stress

Symptoms of a defective brake caliper

An intact brake caliper ensures reliable braking performance in all driving situations. If a brake caliper is defective, typical symptoms often point to the damaged part. For example, when a brake caliper is defective, the car often tends to make unusual noises and vibrations while driving. The reason for this is that the brake pads rub against the brake disc due to the defective caliper. If the caliper of a brake is damaged, the braking force is sometimes distributed unevenly over the individual wheels. As a result, the car pulls to one side when braking. When the brake pedal is depressed, the usual braking effect is also not achieved. When the parking brake is applied, there is not enough force between the caliper and the disc. If the brake pads wear unevenly, a defective brake caliper is a possible explanation.

Typical signs of a defective brake caliper:

• Noises or vibrations
• Brakes pull on one side
• Braking effect is reduced
• Wear on the brake lining
• Brake comfort is poor

Replacing the brake caliper on a car

The brake caliper is one of the most important components of modern brake systems with brake discs. However, there are often signs of damage to the brake caliper, such as cracks or severe corrosion. In this case, the brake caliper must be replaced to ensure continued safety while driving. Only expert auto mechanics should replace safety-relevant components such as brake calipers themselves.

1. Inspect the brake: The brake caliper itself is not always the cause of brake problems. Worn guide pins or a defective brake piston can also be responsible for the problem. Therefore, a thorough diagnosis of the complete brake system is always essential.
2. Prepare for removal: To remove the defective brake caliper, the car is lifted onto a lifting platform or jacked up using a jack and jack stands. The respective wheel can then be removed. This provides good access to the brake and ensures the space needed for the repair.
3. Dismantling the brake line: The next step is to unscrew the brake line. This can cause brake fluid to leak out, which must be collected. To prevent further leakage of the fluid, the brake line is disconnected or sealed using a suitable tool.
4. Remove the brake caliper: To be able to remove the caliper, the brake caliper screw connections must first be loosened. For calipers with parking brake, it is necessary to unhook the brake cable. Then, remove the caliper from the caliper bracket and brake disc.
5. Check components: The brake pad is often damaged by a defective caliper or the pads wear unevenly. Therefore, the brake pads should be checked after removing the caliper. The same applies to the guide pins, dust boots and caliper carrier.
6. Installing the brake caliper: The intact brake caliper is installed in reverse order. To do this, the brake pads are inserted and the brake caliper is bolted to its retaining device. The manufacturer’s specifications with regard to tightening torque and threadlocking must be observed.
7. Install the brake line: After installing the brake caliper, the brake must be reconnected to the brake system. To do this, the brake line is connected at the intended location and tightened to torque. The same applies to the parking brake device.
8. Bleed the brake system: After assembling all components, it is necessary to bleed the brake system. To do this, loosen the bleed screw on the brake caliper and bleed the system according to the manufacturer’s specifications. Any missing fluid must then be replenished and the brake checked again.

What you should bear in mind when replacing the brake caliper

When replacing the brake caliper, there are a number of points to bear in mind. For example, brake dust should not be inhaled, as it is harmful to health. Contact with possibly leaking brake fluid should also be avoided. Depending on the manufacturer and the particular design of the disc brake, the repair procedure may differ. The design of the brake caliper varies depending on the vehicle model. Most production vehicles have a floating caliper with movable bearings. This type of caliper is also known as a fist caliper because it grips the brake disc like a fist. In luxury vehicles and sports cars, on the other hand, brake systems with fixed calipers and multiple pistons are often found.

Checking the complete brakes and brake pistons

When the brake caliper is replaced, all other components of the brakes should also be checked. Since the components of the brake system are disassembled anyway, replacing other parts is particularly easy. Brake parts such as pistons, brake pads, guide pins and brake discs can be easily checked for function and wear during the repair.

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