Bremsenrubbeln trotz neuer Bremsscheibe und Bremsbelag? Ursache + Lösung erklärt am Hyundai i30

The vehicle is first driven to warm up the brakes, and an infrared thermometer is used to measure the brake disc temperature, which reaches almost 100 degrees Celsius. The car is then put on a brake test stand to observe the brake's behavior during partial braking. The brake judder becomes evident as the gauges swing, indicating a pulsation even with constant pedal pressure. Reheating the brakes to nearly 200 degrees Celsius on the test stand allows for observation of side runout.

The wheel is removed to allow a clear view of the brake disc, which shows slight discoloration and haze from the heat. A dial gauge is set up against the brake disc to measure side runout, ensuring the disc is firmly pressed against the wheel hub. The measurement initially shows minimal runout, suggesting the brake disc itself is not the primary problem. This process is repeated with a second dial gauge and then on the passenger side to confirm consistent and low runout.

Since the brake discs are not the issue, other components are inspected. The suspension parts, various joints (wishbone, tie rod end, ball joint), and the wheels/tires are checked for any damage, cracks, looseness, or imbalances that could transfer vibrations to the brakes. The inside of the brake discs is also examined for inconsistencies.

Upon closer inspection of the brake discs, especially on the inside, contact marks and localized spots are identified where the brake pads have left an impression. This often occurs when the vehicle has been stationary for an extended period, and the brake pads were pressed against the discs at those specific points, leading to uneven wear and judder. To rule out wheel imbalance, the front wheels are placed on a balancing machine, showing minimal imbalance (10 and 5 grams), which is deemed acceptable and not a cause of the brake judder.

The brake caliper carrier is removed, and its guides are checked for smooth movement. The guides are cleaned with a wire brush and a specialized file. Ceramic paste is applied to the clean guides. The existing brake discs show deep damage that cannot be rectified, confirming the need for replacement. The wheel hub is thoroughly cleaned using various tools to ensure a perfectly flat and clean surface for the new brake disc, preventing future contact issues.

It is crucial for the brake pads to move freely within their brackets, which is demonstrated to be difficult with the old, dirty components. The brake caliper is then cleaned, and debris is carefully scraped off the brake piston to ensure a clean contact surface. The screws for the brake caliper carrier are cleaned and, as they are not stretch bolts, can be reused with thread locker. New shims are installed onto the caliper carrier, prepared with ceramic paste on the contact areas for the new brake pads, and the carrier guides are lubricated.

The new brake disc is mounted. A tool is used to hold one brake piston in place while the other is extended by gently pressing the brake pedal. This helps assess if the piston moves smoothly or with resistance, and to push out any dirt. The process reveals a significant amount of dirt and debris around the piston, which is then cleaned. The piston boot is inspected for rust or damage. This procedure is repeated for the other side to ensure both caliper pistons operate correctly.

Torque specifications for all bolts are obtained from technical documentation. A system is used where technicians mark tightened bolts with a specific color to indicate that they have been properly torqued, ensuring accountability and safety. After assembling everything, the wheel is spun to ensure it rotates freely without any binding. The wheels are mounted, and an initial test drive is performed with careful braking to bed in the new brake pads and remove any protective coating from the discs. Finally, the vehicle returns to the brake test stand to confirm the absence of judder, verifying the repair's success before returning the car to the customer.