Audi A4 B9 Rear Brake Caliper Housing Brake Unit Right O/S 300X12 8W0615404

Audi A4 B9 Rear Brake Caliper Housing Brake Unit is an original brake system component designed for use with a 300x12 mm rear brake disc. As part of the Brake Calipers and Brackets group, it ensures proper brake pad guidance, stable mounting, and even distribution of braking force to the passenger-side wheel. Using this OEM component allows for an economical yet technically correct repair of the brake system in the Audi A4 B9 generation.

Specifications and technical data

• SKU: 8W0615404
• Mark: Audi
• Condition: Used
• OEM Part Number: 8W0615404
• Substitutable numbers: 8W0615404, 8W0 615 404
• Location on the vehicle: Rear, Right
• Category: Calipers & Brackets

Purpose and function in the brake system

The presented rear brake caliper is designed for installation on the right side of the rear axle in an Audi A4 B9, in a configuration with a 300x12 mm brake disc. It is responsible for the precise guidance of the brake pads relative to the disc, maintaining proper pressure, and ensuring the stable operation of the entire brake module on that wheel.

Thanks to its factory geometry and correct body offset, the caliper works with the original carrier, hub, and disc, maintaining the correct operating position of the pads. This is crucial for maintaining even pad wear, predictable braking force, and the correct operation of assistance systems, such as the electronic stability control.

Construction and performance parameters

The caliper body is a rigid, one-piece "housing brake unit" designed for the stock Audi A4 B9 brake system. The construction ensures:

• adequate rigidity under loads generated during rear axle braking,
• stable piston and brake pad guidance throughout the entire operating range,
• compatibility with stock mounting elements and the brake line.

Selecting this specific caliper for the 300x12 mm disc allows for maintaining factory braking characteristics without interfering with the force distribution between the front and rear axles. This is important both from a safety perspective and for the proper functioning of electronic driver assistance systems.

Benefits of using an original Audi caliper

Using an original Audi rear brake caliper instead of a worn or damaged component provides a number of practical benefits:

• Factory fitment – preservation of original mounting points, correct geometry, and compatibility with other brake system components.
• Stable braking characteristics – no need to modify discs, pads, or lines, which facilitates service and diagnostics.
• Economical repair – the used OEM component allows for cost reduction while maintaining compliance with the vehicle's factory design.

For workshops and individual users, this means easier installation, a predictable repair outcome, and a lower risk of compatibility issues in the future.

Vehicle placement and installation aspects

This caliper is intended exclusively for the rear right side of the vehicle. Correct placement on the rear axle is important due to:

• the direction of the bleeder screw and proper system bleeding,
• brake line routing and protection against abrasion,
• maintaining the correct operating direction of the mechanism relative to the disc.

During installation, it is recommended to use the appropriate tightening torques for mounting bolts and to check the condition of the disc and pads to fully utilize the potential of the newly installed caliper.

Product condition and practical application

The offered brake caliper is a used component, which allows for a cost-effective restoration of the brake system's efficiency in an Audi A4 B9. This solution is particularly attractive for post-accident repairs, replacing a single damaged caliper, or during the gradual renovation of the rear axle.

In combination with properly selected discs and pads, the rear right brake caliper allows for the restoration of stock braking parameters without the need for structural vehicle modifications or changes to Audi's factory solutions.

If you are planning a comprehensive repair or upgrade of the braking zone in your Audi and need other elements from the same group, such as additional calipers, carriers, or mounting brackets, check the available parts in the Audi Brake Calipers and Brackets category.

When selecting used brake system components, it is worth following a proven procedure for assessing technical condition and compatibility – you will find practical tips in the article Second-hand brake system: how to safely choose discs, calipers, and ABS?, which serves as a useful checklist for an informed purchase.

If you are considering a broader upgrade or repair of your Audi using second-hand parts, you will also find inspiring examples and advice in the material Audi on second-hand parts – tuning and repairs without losing quality, which describes how to combine savings with maintaining the character of German automotive engineering.