How to change the front disc brakes on your E23 7-series (long)

Subject: How to change the front disc brakes on your E23 7-series (long)
Author: DavidC (moderator) : member since December, 2003 : 11918 posts
Posted on: 2004-06-01 02:27:32

The front end of my '86 735i was shaking during braking. All of the front-end components had already been replaced as part of a full overhaul of the suspension, so the likely cuplit was warped rotors. As it turns out, that was indeed the case. After replacing the front rotors and pads, the car brakes perfectly smoothly again.

My wife and I are shadetree mechanics and diehard BMW enthusiasts. We've had a heck of a good time restoring our '86 735i together over the past ten months, and our '97 740iL before that. We've never done a brake job before, however, so this was our first foray into the world of rotors and pads. Although a professional mechanic might scoff at our liesurely pace, the job turned out to be easier than expected. We were, after all, stopping every few minutes to snap photos and make notes for the BimmerBoard writeup!

If I had a number one suggestion to make, it would be to use an air wrench. You can use a regular socket wrench, of course, but the job goes sooooo much easier with the power tool.

What you'll need:

New brake pads (two per wheel, purchased as a set)
New rotors (one per wheel)
17mm socket
19mm socket
5mm hex bit
3" socket wrench extension
Torque wrench
Ratcheting socket wrench or, preferably, an air wrench
Brake cleaner spray (the non-chlorinated type is preferable)
CRC Disc Brake Quiet or similar compound
Anti-sieze lubricant
Hammer
Small philips screwdriver
Paper towels
GoJo or other degreasing hand cleaner for cleanup
Optional: 8" gear puller (available for rent at AutoZone)

The new front rotor and pads. This is for one wheel. You'll need another set just like this for the other front wheel, too. Rotors and pads should always be changed in wheel pairs. I elected to go with OEM rotors but Mintex pads, which are reputed to be as good or better than OEM but with lower dust. They were purchased from BMA Auto Parts. The cost was $38 each for the front rotors and $29 for the set of front pads, plus shipping.

A tube of anti-sieze lubricant lubricant like this will make your life easier the next time you change the rotors. We'll apply it to the moving pins of the calipers and, more importantly, to the inside surface of the rotor where it meets the mounting plate for the lug bolts. This will prevent rust from forming which can sieze the two parts together.

Jack up the car and remove the wheel. The lug bolts are 17mm. Once the wheel is off, it helps to turn the wheel all the way out to have better access to the backside of caliper assembly. Don't forget to use jackstands for safety.

A closeup view of the front of the caliper assembly. The little black wire is the brake pad wear sensor.

Disconnect the connector for the brake pad wear sensor. Only the left front and right rear wheels have the sensors.

Attempt to unscrew the clip securing the hydraulic line. This will give you more room to move the caliper around when we remove it. In my case, the screw was rusted solid so I just left it alone.

A view of the backside of the caliper from within the wheel well. Using a 19mm scoket, remove the two bolts that secure the caliper assembly to the wheel.

Pull the caliper assembly away from the wheel. Set it on a box or hang it with a piece of wire from the spring to avoid stressing the metal hydraulic line.

Remove the two caliper pins by tapping them with a small nail or screwdriver and a hammer.

Remove the two pins and the spring clip.

Remove the pads from the caliper assembly.

Your new pads should come with a new brake pad wear sensor like the one shown above.

Install the sensor into the notch of the new pad. Remember, the sensor goes on the pad that grips the inside edge of the rotor.

Use a C-clamp to gently open the pistons in the caliper assembly. Watch the fluid reservoir in the engine compartment as the pressure may cause it to back up into it.

Apply anti-squeal compound to the metal sides of the new pads. I used CRC Disc Brake Quiet, readily available at Advance Auto Parts and similar places.

Install the new pads into the caliper assembly.

Insert the caliper pins into the assembly along with the spring clip. Apply a bit of anti-sieze lubricant to the inside areas of the pins, but not the parts of them that stay in the holes.

Remove the rotor set screw using a 5mm hex bit.

If you're lucky, all you'll need to do is knock the rotor loose with a hammer. If you're not lucky, like me, you'll have to employ more serious measures to get that sucker loose.

I used an 8" gear puller ($40 at Auto Zone) to remove the rotor from the hub. The shiny metal plate is there to protect the hub from the sharp end of the gear puller. Remember to wear eye protection when using the gear puller. When the rotor suddenly breaks free, it can throw bits of rust at you. It only took a few turns of the air wrench and POW!!! The rotor was off in a jiffy.

The old rotor being removed from the hub.

A view from above the wheel assembly. The black, rectangular object with a beveled edge and a wire on the opposite end is the ABS pulse sensor.

Being curious, I had to remove the ABS pulse sensor to see what it looks like. After removing the 5mm hex bolt securing it to the wheel, it just pulls straight out. Be careful not to damage the O ring seal.

The inner and outer sides of the rotor are covered in an oily film applied at the factory. Spray brake cleaner on the inner and outer sides of it (where the brake pads will grip it) to remove the film and any grease that may happen to be there. Wipe away any residue with a paper towel. We want the pads to be able to grip the metal without any lubricants in the way. Before installing the rotor, apply some anti-sieze lubricant to the inside wall where metal meets metal for the lug nuts. This will prevent the formation of rust so that the rotor can be easily removed when it's time for it to be replaced.

Install the new rotor onto the wheel assembly, then line up the holes and insert the rotor set screw. Torque to 14 foot-pounds.

Attach the caliper to the wheel assembly. Re-connect the brake pad wear sensor plug (left wheel only). Torque the two 19mm bolts on the backside of the caliper assembly to 81 foot pounds.

A view of the completed installation, with new pads, brake pad wear sensor and a new rotor.

Mount the wheel and tighten the lug bolts by hand. Torque to 81 foot pounds after lowering the car off the jack.

If you want to get really fancy, re-paint your lug bolts with Rustoleum satin black spray paint while they're off the wheels.

David Cecil
'02 X5 3.0, 15k miles
'97 740iL, 120k miles
'86 735i, 94k miles
'77 320i, 140k miles
'92 325is (rear-ended on I285, gone but not forgotten)

www.e38.org has links for everything about your BMW 7-series automobile

The 7 Series E23 Forum | Message Thread:

How to change the front disc brakes on your E23 7-series (long) (pic) (url) - DavidC 2004-06-01 02:27:32 (13805 views)
- Follow-up: Painting the calipers and rotors (url) - DavidC 2004-06-09 17:43:49 (991 views)
- Nice write-up and pictures. - kff 2004-06-01 16:15:44 (679 views)
  - Ok, you inspired me to take it all apart again. - DavidC 2004-06-03 19:33:58 (661 views)
    - The brake painting project results (url) - DavidC 2004-06-03 23:08:14 (784 views)
  - Corrections and questions - DavidC 2004-06-01 22:37:15 (775 views)
    - Re: Corrections and questions (pic) - B5M2W8 2004-06-02 11:38:23 (975 views)
    - The pulsing of the brake, is that when you are > - kff 2004-06-02 11:37:13 (794 views)
      - It happens when using the brakes shortly after putting the car in gear. - DavidC 2004-06-02 13:57:21 (748 views)
- great work...i did the rears on my car with the same procedure you use - elmoreandrew 2004-06-01 10:11:56 (660 views)

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