The brakes on any vehicle must be working properly to ensure safety while driving. If the brakes are not functional, it may not be possible to stop the vehicle in the way that the driver sees fit. This may mean not having enough power to stop, or stopping too quickly and abruptly. There are two main components that comprise the brake system: The brake pads and the brake disc. You can replace both of these components on a BMW 325i to keep them at optimal functionality.
Engage the parking brake on your vehicle. Note that if you are changing the brakes on the back tire, you cannot engage the parking brake, as it will block access to the brakes. Just ensure that you are in "Park."
Lift up the vehicle near the tire of the brake you are replacing using your car jack.
Remove the wheel to access the brake system by removing the bolts.
Remove the dust caps that protect the caliper guide pins by pulling them gently with your hands. There should be two of them located on the inside of the caliper system, one on the top and one on the bottom.
Remove the hex bolts while securing the caliper guide pins, so the bolts can turn freely. Remove the pins after you have unscrewed the bolts. Set both in a safe place, as you'll have to re-install them later.
Press in the spring clip away from the center of the disc using a clamp, then remove it by prying it away with a screwdriver or similar tool.
Remove the brake pads and caliper by sliding them out.
Secure the caliper in place by tying it with a rope, so the brake pipes are not stretched.
Press in the caliper piston while ensuring that the brake fluid levels are appropriate.
Remove the brake carrier by removing the two bolts that secure it.
Remove the brake disc by removing the Allen bolt that secures it. It will be difficult to remove due to rusting; however, you can tap it with a hammer to loosen it.
Clean all areas of the system that seem dirty. Coat the area with anti-seize compound.
Attach the new disc and secure it with the Allen bolt.
Reattach the brake carrier and secure it with the two bolts.
Attach the new brake pads to the caliper. Slide the caliper back into position.
Secure the caliper guide pins around the caliper. Be careful not to over-tighten.
Reattach the dust caps
Reattach the wheel.
Test your brakes immediately. Torque values may have to be adjusted based on your driving feel. These values may be found in your owner's manual.
