why does my BMW 3 Series E90/E91 shake when I brake hard?

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a flat surface and engage the parking brake.

2. Wheel Removal

• Use a jack to lift the vehicle and secure it with jack stands.
• Remove the wheel lug nuts with a socket wrench.
• Take off the wheel to access the brake components.

3. Brake Rotor Inspection

• Use a dial indicator gauge to measure the thickness of the rotor at multiple points.
• If warping is detected (more than 0.002 inches), proceed to replace the rotors.
• Clean the hub surface with brake cleaner and a wire brush to ensure proper rotor seating.

4. Brake Pad Inspection and Replacement

• Remove the caliper bolts with a socket wrench and carefully slide the caliper off the rotor.
• Inspect brake pads for even wear; replace if thickness is below 3mm.
• Install new pads, ensuring they are properly seated in the caliper bracket.

5. Reassembly

• Reinstall the caliper and tighten the caliper bolts to the manufacturer’s specifications (usually around 25-35 ft-lbs).
• Reattach the wheel and hand-tighten the lug nuts.
• Lower the vehicle and use a torque wrench to tighten the lug nuts to the specified torque (typically 80-100 ft-lbs).

6. Test Drive

• After reassembly, conduct a test drive to confirm the repair was successful.