Brake Pads (Front)
Page 1 of 2: Removal

Step 1: Remove Front Wheels

With the car on the ground loosen the five wheel lugs (on both sides) using either your factory wrench or a 1/2" driver with 3" extension and (19mm?) socket. Raise the front end of the car (refer to front jacking procedure) and remove the wheel lugs the rest of the way. Remove the front wheels.

Fig 1: Loosen the wheel lugs the rest of the way, once the car is in the air.

Fig 2: Brake caliper and rotor revealed.

Step 2: Remove Brake Anti-Rattle Clips

The brake clips (shown here being reinstalled) are easily removed using a pair of screwdrivers. Pry one screwdriver between the hub and clip (where my fingers are holding the clip in Figure 3). This frees the two little catches (see Figure 3) and enables you to use a second screwdriver (wedged against the caliper) to pry the clip towards you and off the caliper.

Step 3: Remove Caliper Guide Bolts

Reach behind the caliper and carefully pry out the two small rubber dust caps (see inset, Figure 4) using your fingernails. This reveals the two 7mm allen-head caliper guide bolts (see Figure 4) which secure the caliper to the car.

Remove the two guide bolts. Use a 3/8" driver with a 7mm allen-head tip. This tip is available at most auto supply stores for about $5 and may actually be labeled a "disc brake caliper socket". You may need to give the driver a light rap with your 3-lb hammer to brake the bolts loose but these were not difficult to remove.

Step 4: Remove Brake Pad Wear Sensor (Left-Front, Right-Rear Only)

Your M3 has two brake pad wear sensors. The front sensor is located on the left-hand side and the rear sensor is located on the right-hand side. The front brake pad wear sensor runs from a wiring harness mounted to the inside of the wheel-well, around the strut (and secured by a clip mounted to it) and then back to the caliper. The small rubber cap on the brake-fluid release valve also serves to route the green sensor wire (see Figure 5).

Using a pair of needle-nose pliers, carefully remove the ceramic end (Figure 6) of the brake pad wear sensor from the worn brake pad. This sensor does not necessarily need to be replaced, but the ceramic tip is fragile so it is a good idea to pre-emptively buy an extra sensor in case you break the old one when removing it. If you choose to replace the sensor, the far end of it is located in the plastic harness box mounted to the inside of the wheel-well (Figure 7). On the left-hand side (pictured) this box contains connections for both the brake pad wear sensor (right) and the ABS sensor (left). To disconnect this end of the brake pad wear sensor, open the plastic box and snap the lower end of the wire out of the slot where it is seated. Next use your fingers, or a small screwdriver, to depress the plastic clips while pulling the harness apart.

Fig 6: Exposed ceramic end of the brake pad wear sensor.

Fig 7: Harness end brake pad wear sensor (right) and ABS sensor (left).

Step 5: Remove Caliper

The calipers may be difficult to remove, particularly if your rotors are very worn (in which case they will have a lip). You can use a flathead screwdriver, inserted into the brake pad wear sensor hole in the pad, to gently pry the pads away from the rotors. In practice, I found this difficult to do and didn't have too much trouble simply removing the caliper without spending a lot of time on this step.

Gently pry the caliper (Figure 8) away from the rotor. The inner pad is connected to the caliper and will come out with the assembly. The outer pad, shown in the photo, will remain in place. It is not secured in any way once you remove the caliper so take care not to drop it as you are removing the caliper. Once the caliper has cleared the rotor, simply lift the outer pad off of the carrier mount. The carrier mount is a separate piece of cast iron that is secured to the hub with its own two mounting bolts (see Bentley, p. 340-6, Fig. 8). This carrier need only be removed if you are replacing your rotors as well as your pads.

Finally, suspend the caliper (Figure 7) from the strut assembly. Untwist a coat hanger and thread the wire through both the caliper and the spring. Ensure that no pressure is placed on the brake hose. Note: In the photo below, you can see the old inner brake pad which is still clipped to the caliper.

Proceed to Step 2: Brake Pad Reinstallation or replace your rotors, first.