In this tech article we will discuss replacement of the rear brake pads on the E30 BMW. While this tech article is specific to the E30, it applies to most other BMW models with floating calipers as well.
I had begun to notice that my brakes had started to squeak a bit. Shortly afterwards, I noticed the "brake linings" light come on in the dash. This is a a visual system BMW uses to indicate that the brake pads will soon need replacement. As I did before with the front brakes, this article covers the replacement of the rear brakes.
I started by ordering up new brake pads and brake pad sensor from Pelican, of course and began the process. That said here's how it is done.
First, loosen the lug bolts but do not remove them. Just loosen them, then snug them up. Next, jack up the car in a safe manner.
Once the wheels are removed you will see the disc brake assembly. Look at the backside of the caliper. You'll see an electrical connection coming out of the right rear caliper. This is the wire harness for the rear brake wear sensor. Unplug this sensor where it plugs into the harness, as shown in the photo.
Now look at the rear calipers, you will notice two plastic grommets at the top and the bottom of the caliper. You will need to remove these in order to continue. Once you have them out, use an Allen wrench to remove the two bolts at the top and the bottom of the caliper. Once removed, the caliper should slide off.
Now, take a look at the old brake pads. You can see how worn they are from the pics. Compare these to the new pads. Notice the brake wear sensor on the old pads. This will give you a good idea of how the sensor works. Essentially when the pads wear down to a certain point, it wears away the outside cover of the sensor, eventually wearing it down enough to the point where the metal strip inside contacts the rotor, and completes the electrical circuit, and the light on the dash illuminates. We will be replacing these sensors as well.
The next step is to remove the brake rotors. You need to remove them in order to have them surfaced. Re-surfacing brake rotors is important. Failure to do so can cause the brakes to not seat properly or even overheat. Re-surfacing insures that the new pads will seat properly. Any decent auto parts shop can re-surface your brake rotors for usually around $5 a rotor.
Keep in mind, however that brake rotors, by law, can only be re-surfaced a certain amount of times before you exceed the amount of material that can be removed. This is done for safety reasons. If you have exceeded the amount of material that can be removed, you'll have to purchase new rotors.
In order to remove the brake rotors, remove the Allen head bolt that holds the rotor to the hub. You may have some trouble removing these without stripping the bolt, so I recommend that you soak the bolt in a good penetrant spray for a few hours prior to loosening the bolt. This will help prevent against stripped or damaged threads, and a potential nightmare that will send you screaming over the edge. (Ask me how I know this....)
The next step to remove the rotors is to remove the brake caliper bracket that sits on the back of the hub. You will notice two large bolts holding it to the hub. Remove these two bolts, and remove the caliper bracket. The brake rotor should now come free.
Once you have the brake rotors removed, take them to the auto parts store, machine shop, etc.. and have them re-surfaced. Obviously, take another car to the store, as you'll find your brakes don't work with the brake discs removed from the car.
Now is a good time to clean everything. You'll want to use a good quality brake cleaner to make sure that the calipers and surrounding parts are clean and free of dirt and grime. Grease on the brake discs can cause brake failure.
With the brake discs surfaced, you can now start re-installing the components. Put the surfaced rotors back on the hubs, and make sure to line up the holes, so that the brake disc hold-down Allen bolt will thread in. It's a good idea to put a dab of anti-seize compound on one side of the threads to prevent stripping the next time you remove the brake discs.
Now that the rotors are installed, it's time to compress the caliper pistons. You'll want to do this in order for the new brake pads to fit. As the old brake discs wear, the piston gradually comes more and more out of the caliper, making it impossible for the new pads to fit.
In order to compress the pistons, first remove the brake fluid reservoir cap, this will relieve the pressure on the system, and make it easier for you to push the pistons. Next, use a large C-clamp as shown in the photo, to slowly push the piston back into the caliper. The caliper pistons should slide back with a minimal amount of force.
Now, install the new brake wear sensor in place. Keep in mind that there is only one brake wear sensor on the right rear. The sensor simply clips onto the brake pad as shown in this photo.
Once the calipers are compressed, re-install the caliper bracket on the hub and make sure the bolts are tight. BMW recommends you torque them to 65 ft/lbs.
Next, place the new brake pads on the lower caliper mounting plate as shown.. When they are in place, carefully place the caliper over the pads. You may notice a bit of resistance in doing this because of the new springs that hold the new pads in place. Just use a little force to push the caliper in position, then install the two Allen head bolts and tighten them. Don't forget to put the plastic grommets back in place. These grommets prevent grime and dirt from building up on the bolts, which could eventually cause them to rust and sieze.
Once all this is done, re-check everything. You don't want to take chances with your brakes. Check and then double check that everything is tight.
Now you are ready to put the wheels back on. Once they are re-installed and tightened, take the car out and test the brakes. You should notice that they don't stop very well at first. This is normal. You'll need to seat the brake pads in order for them to work well. Simply drive the car cautiously for roughly 50 or so miles, and the brake pads will seat into the new rotors. It's also a good idea to pump the brake occasionally during this time to get the rotors hot and the pads seated quicker.Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.