E34 Front Brake Pad and Rotor Replacement

I recently replaced the front brake pads and rotors on my E34 1995 BMW 540i; here are a few pictures...  Click on any picture to enlarge it.

You may wish to open another browser and check out these diagrams as I run through the process; you may find them helpful: Front Rotor Diagram and Brake Assembly Diagram

I had checked my rotors and learned that they were worn enough to need replacement.  Using a micrometer I measured the breaking friction surface at about a dozen different spots, and then taking the smallest measurement, I compared it against the 540i "wear limit" above.  (Minimum allowable thickness is stamped on stock rotors).  My measurements were smaller than the minimum - my rotors were toast.  Additionally, it seems that stock rotors use a slightly softer metallurgical mix, making them "stickier" so to speak, for quicker breaking.  Unfortunately, so I'm told, this tends to limit their lifespan after reconditioning.

Materials

So, I began to gather the parts I needed.  I knew I'd need to buy two front rotors since they are always replaced in pairs.  After reviewing the online forums and other documentation I decided that I'd like to try rotors and ceramic pads from Raybestos.  The old pads were by Pagid with stock rotors.  I had no complaints, but the new setup seems quieter and stops faster.  Below is the parts list:

• 2 rotors - Raybestos PG Plus VSM, 96329 ($21.79 each at RockAuto.com)
• front pad kit - Raybestos PG Plus QuietStop, PGD394QS ($49.79 pair at RockAuto.com, covers both front brakes)
• brake pad wear sensor - BMW, 34 35 1 179 820
• brake cleaner spray
• penetrating lubricant - e.g. WD 40
• 6mm hex socket
• 19mm socket
• 19mm box end wrench
• ratchet handle and extensions
• lubricating compound - a.k.a. "anti-squeak compound"
• anti-seize compound
• 6" C-clamp
• tongue-and-groove pliers - a.k.a. Channel-lock pliers

You may also find a torque wrench helpful if you'd like to set the tightening torques "by the book" and you don't have the mechanics "feel" for such things (or, you just like to be exact).

Also, if you have a handheld impact driver available, you will find it helpful for removing Allen and Torx screws without rounding them off.

Impact drivers are available for less than $25 (00947641000 at Sears.com)

Getting Started

This procedure does not require you to remove or loosen the brake fluid hose.  If, however, you inadvertantly do remove or loosen the hose you will need to bleed the entire brake system.

After you lift the car and secure it with stands, remove the wheel.

Here, I am pointing at where I sprayed some penetrating lubricant into the 6mm rotor mounting screw.  To clean the brake assembly I sprayed it with brake cleaner.

Pry off the anti-rattle clip with a screwdriver.

Here is the anti-rattle clip removed from the car.

Here is the caliper with the anti-rattle clip removed.

On US models, the brake pad wear sensor is on the driver's side (left) caliper.  Unplug it.  Also note how the sensor wire loops through the dust cap on the brake ventilation valve (a.k.a. "bleeder screw").  Temporarily open the dust cap and remove the sensor wire and then close the dust cap again.

Also, remove the brake hose grommet from its bracket on the lower strut.

Here is a picture looking upwards at the lower 19mm mounting bolt holding on the caliper.  I sprayed on some penetrating lubricant.  Nevertheless, I had to work at removing this bolt.  The mounting bolts are tightened to 110 Nm (81 ft-lb).

Here is a picture looking downwards at the upper 19mm mounting bolt.  Remove both the top and bottom mounting bolts.  Later, before these bolts are reinstalled, it's good to put a little anti-seize on them.

If your brake reservoir is topped all the way up, remove a little fluid.  The next steps will compress the caliper piston displacing some fluid back into the reservoir.

Slide the caliper assembly off the rotor.  Remove the old pads.  Check the piston's dust boot (seal) to make sure it is not torn or cracked.

Using channel-locks, or the C-clamp, compress the piston into the caliper.  I like to use a block of wood between the C-clamp and the top of the piston.  This prevents the piston from being pushed in at an odd angle.  Don't forget to support the caliper to the frame with a strong wire; don't let the caliper hang by its brake hose.

Separate the brake pad carrier from the brake carrier.  It should slide out easily.

Clean brake pad guides on brake caliper and brake back plate and thinly coat with anti-squeak paste.

Note the caliper guide screws (bushings) on the brake carrier.  These should be shiny and smooth.  Only clean these screws, do not grease.  Replace the guide screws if they are scratched or rusted.

Here are pictures of the brake pads I used.  Here are front and back pictures of the pad and its anti-squeak plate.

I assemble the anti-squeak plate to the pad and apply some lubricating compound (anti-squeak) to the plate for good measure.  I smear it around with a gloved finger to make sure it is covered well.  This reduces the high frequency vibrations between the caliper piston and the pad resulting in the characteristic high pitched "squeal."

On the driver's side (left) caliper, you also must install a brake pad wear sensor.  Here are front and back pictures of the pad and its anti-squeak plate along with the brake pad wear sensor.  The wear sensor does not come with the pads; I bought one from BMW.

If you look closely at the head of the brake pad wear sensor, you will notice that one side is thicker with a raised half-moon-like "bump."  In the picture it is the side nearest the camera.  There is a small wire embedded in the plastic of this "bump."  The idea is that when a pad wears down so far that the "bump" is worn down too, the wire in the plastic is either severed or grounded thus triggering the brake lining warning.

Install the wear sensor on the new pad.  Note how the "bump" is faced toward the side with the friction material.  Notice that there is a pre-manufactured slot in the brake pad designed to accept the sensor.  Ensure that this area is free of dirt, friction material, and excess paint.  The sensor can be easily cracked if too much force is applied to push it onto the pad.  An easy way to break a sensor is to try to force it into place upside down.

Assemble the anti-squeak plate to the brake pad.

Apply lubricant (anti-squeak) compound to the plate.

Getting it Together

Putting everything back together is a straight forward process.  Some seem to have a "feel" for how tight everything should be.  If you don't (like me), and you have a torque wrench here are the various torque specifications below.

Fundamentally, installation is the reverse of disassembly.  Do not contaminate the pad or rotor breaking surfaces with lubricant or grease, etc.

You may also wish to clean and lightly file the hub while the rotor is off to remove any debris or high spots that may cause the rotor to have runout when bolted back on.  In the picture above you can see shiny spots where the file removed material from high spots.  After a couple of light passes the micrometer shows a runout of less than .0005   (pictures & text credit: Bill R.)

Apply some anti-seize to the hub.  Install the rotor and torque the 6mm mounting screw to 16 Nm (12 ft-lb).

Again, installation of the caliper is reverse of removal.  It is good to ensure no lubricant contaminates the rotor or pads.  The rotor may be cleaned with break cleaner.  A wise second step is to wash the rotor with a warm soap and water solution.  This will remove any remaining traces of preservative lubricant or excess solvent from the micro-finish.  Be sure to handle the pads carefully, avoiding greasy fingerprints, etc. that might contaminate the friction surfaces.

Depress the brake pedal several times to adjust the caliper and pads.

"Bedding In" Your New Brakes

After you have completed your work, it is a good idea to perform a process called "bedding in" on the brakes.  This process will mate the new pads to the rotors.  A transfer of material occurs between the pad and rotor surfaces, thus conditioning the rotors micro-finish.  This pad/rotor break-in serves to stress-relieve the rotors and creates a compatible pad/rotor package.

Accelerate to about 40 mph.  Bring the vehicle to nearly a complete stop.  Remove your foot from the brake pedal, and accelerate again to 40 mph.  Apply moderate brake pressure again, bringing the vehicle to nearly a complete stop.  Repeat this 12 to 30 times.  Drive about 1/4-mile between each braking.  To prevent localized hot spots on the rotor, do not sit with the brake pedal depressed immediately following one of these deceleration runs.

Contents

• Radiator Repair Guide - Need to replace the radiator? No problem. Take your time; it's not that hard.
• Brake Pad and Rotor Replacement - What should you do when the brake lining message comes on? Replace your brake pads and, sometimes, your rotors. Take an afternoon; BMW makes it easy.
• M60 V8 Engine - The M60 V8 Engine. A solid, powerful, low maintenance motor.
• CD Changer - The car's all wired for a CD changer. How do I hook it up?

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