Here you will find useful information and handy tips relating to changing brake discs, brake pads, and brake calipers using the example of a BMW 320i (E90).

Brake pads and brake discs are some of the most important wearing parts on vehicles. A whole host of details needs to be considered when replacing them in order to ensure the necessary degree of safety after the repair work. On this page you can find out the steps required when removing and installing brake discs, brake pads, and brake calipers as part of professional repair work.

Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.



For illustration purposes, a BMW 320i (E90) is used in the following repair note as an example, but this can also apply to other vehicle models equipped with brake calipers of the same type. The schematic illustrations, figures, and descriptions are for explanation and presentation of the document text only, and cannot be used as the basis for carrying out the repair.


Repair work to brake systems may only be carried out by qualified specialists. When carrying out any repairs on the brake system, you must follow the maintenance and safety instructions of the vehicle manufacturer and the product-specific assembly instructions.


  • Drive the vehicle onto a lifting platform ✓
  • Remove the front wheels ✓

Carry out a visual inspection

Before carrying out the repair, it is advisable to check all relevant components in the area of the axle and wheel brake, such as the tires, brake hose, and transverse control arm, for example, for damage.

  • Defective parts must be replaced without fail ✓

Remove the brake caliper, take out the housing retaining spring

  • Push the retaining spring in the direction of the arrow against the spring force and remove sideways ✓
  • Check the retaining spring for damage and replace if required ✓


When repairing the brakes of vehicles that are more than 48 months old, we also recommend that you have the retaining spring replaced.


The retaining spring is preloaded. If it jumps sideways it can cause injury.

Unclip the wiring harness of the brake pad wear indicator

  • To do so, open the connector housing (1) in the wheel well, unlock the connector, and detach the wiring harness from the combination holder (2) ✓

The following component connections are securely fixed in the combination holder on the suspension strut:

  • Wear indicator for brake pad (A)
  • ABS sensor (B)
  • Brake hose (C)

Remove the protective plugs of the guide bolts

Inspect protective plugs and damping sleeves for damage.

  • Defective parts must be replaced without fail ✓


Water and dirt ingress cause corrosion on the guide bolts, which will impair the function of the brake caliper. This in turn leads to one-sided braking behavior and premature wear.

Undo and remove the two fixing screws

Tools required:

  • 7 mm Allan key ✓

Remove the brake caliper from the brake anchor plate

Pull the brake caliper back and off. Then take the outer brake pad out of the brake caliper.

Remove the brake pad on the piston side

As the brake pad on the piston side is mounted with a retaining spring in the piston, it must be pulled forward in order to remove it. Take the wear indicator out of the pad.


As the wear indicator loses its adhesion once it has been removed from the brake pad, this must always be replaced once removed.

Tie up the brake caliper on the suspension strut using a suitable hook

  • In doing so, avoid twisting or kinking the brake hose ✓
  • Detach the brake hose at the holder on the suspension strut if necessary ✓


To avoid damage, do not leave the brake caliper hanging from the brake hose!

Slacken and unscrew the fixing screws of the caliper anchor bracket

  • Remove the caliper anchor bracket and check it for damage ✓

Check the minimum brake disc thickness

Check the wear limit of the brake disc using a suitable tool.

  • Place a gage at several measuring points (A) over the friction ring and take measurements ✓
  • Compare the lowest value with the reference value (minimum thickness) ✓

Reference value

The reference value in millimeters is stamped on the outer edge or on the brake disc pot.

  • MIN TH = Minimum Thickness ✓
  • If the thickness falls below this reference value, replace the brake disc ✓

Remove the brake disc

  • Undo the fixing screw ✓
  • Remove the brake disc ✓


If the brake discs are sticking, carefully tap the bottom of the brake disc pot with a rubber hammer.

Always remove the brake discs in pairs

New brake pads may only be installed if the minimum thickness of the brake discs (MIN TH) has not been undershot.

Check the wheel hub

  • Check the surface for corrosion and damage ✓
  • Check the thread for damage ✓

Clean the contact face of the wheel hub

  • Remove dirt and traces of corrosion using a suitable tool ✓


Unevenness of the contact face can lead to warping of the brake disc and therefore axial runout!

Protection against corrosion

The contact face of the wheel hub must be undamaged, rust-free, clean, and metallically bright. To protect against corrosion, apply a thin coating of spay oil to the contact face then wipe off with a lint-free cloth.


Do not grease the surface of the wheel hub after cleaning!

  • The grease could come into contact with the brake during rotation.
  • The tightening torque of the rims could then no longer be ensured.

Mount the brake disc

Mount the brake disc and fasten with fixing screw.


Observe the tightening torque!

Prepare the caliper anchor bracket for mounting

The recommended way to do this is to remove the anchor bracket and clamp it in a vise.

  • Clean the anchor bracket with brake cleaner ✓
  • Carefully remove any corrosion on the guide surfaces using a wire brush or file ✓

Install the caliper anchor bracket

  • Insert screws and tighten ✓
  • Observe the tightening torque! ✓


Then apply a thin coating of non-conductive, non-metallic anti-squeal paste to the clean contact faces of the caliper anchor bracket.


It is essential to avoid mechanical damage to the guide surfaces!


Push the brake piston right back

Push the brake piston right back using the reset tool.

  • Check the dust protection sleeve of the piston for damage ✓


Observe the brake fluid level in the expansion tank when pushing back the pistons. Drain the tank beforehand if necessary.

Clean the brake caliper with brake cleaner

Thinly coat the contact face (A) of the brake piston with anti-squeal paste.

  • Clean the contact face (B) and also thinly coat with anti-squeal paste ✓
  • Clean the contact face (C) of the hammer heads / brake calipers and thinly coat with anti-squeal paste ✓

Install the brake pads

  • Thinly lubricate the brake pads only at the hammer head (E) and in the area of the contact faces (F) on the brake caliper using a non-metallic anti-squeal paste ✓
  • Insert the outer brake pad in the caliper anchor bracket ✓
  • Insert the pad on the piston side in the brake caliper ✓
  • Fit the brake caliper on the caliper anchor bracket ✓


New brake pads may only be installed if the brake disc is thicker than the minimum brake disc thickness (MIN TH).

Clean and check the guide screws

  • Check the thread ✓
  • Damaged screws must be replaced without fail ✓


After cleaning, grease the contact surfaces of the guide screws with a thin coating of grease. Use only a silicone-based grease in this area.


The dust protection sleeve of the brake piston and the protective plugs and damping sleeves of the caliper guide must not come into contact with oils or greases based on mineral oil. They could be damaged due to swelling of the elastomers.

Mount the brake caliper

Mount the brake caliper and fasten with the guide screws.

  • Reattach the brake hose and wear indicator cable in the combination holder ✓
  • Insert the retaining spring ✓


Observe the tightening torque!

Install and connect a new wear indicator

  • Make sure the wear indicator is seated correctly in the brake pad ✓


Clip the cables and brake hose back into the combination holder.


Make sure that the brake hose is not twisted and is correctly fastened in the holder.

Establish the working position

Press the brake pedal several times up to two thirds of the way down, and not further, to enable the brake pads and pistons to take up their working positions.


If you press the pedal down fully, this can damage the brake master cylinder!

Check the level of brake fluid in the expansion tank

Check the brake fluid level in the expansion tank and fill up to the "MAX" marking if necessary.

  • Change the brake fluid if necessary ✓


Only use new brake fluid that has been approved for the vehicle type.

Clean the brake disc

Clean the brake disc after mounting the brake caliper.

  • The friction ring must be free of dirt and grease ✓
  • The disc pot and thread must be clean and free of foreign particles ✓

Mount wheels

  • Clean the rim contact face before mounting the wheel ✓
  • Observe the tightening torque of the wheel bolts! ✓

Service reset

Once the brake pad and wear indicator have been replaced, the Condition Based Service indicator must be reset using a suitable diagnostic unit as specified by the vehicle manufacturer.


The CBS maintenance system analyses the actual service requirement of the vehicle. It measures the condition of the most important wearing parts and operating fluids and monitors the individual service scopes.

Function check and test drive

Once the repair has been carried out, it is essential to perform a functional check of the brake system.

  • Carry out a test drive to run in the brake system according to the specifications of the vehicle manufacturer ✓
  • Check the function of the brake system on the brake test stand ✓


In this case, please observe the general information on braking in new brake discs and brake pads!


Replacing brake pads, brake discs and brake calipers on the front axle

Practical instructions on replacing brake pads, brake discs, and brake calipers on the front axle of a passenger car.


04:52 min