Changing brake pads, brake discs, and brake calipers (type Teves FN) on the front axle
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).
Important safety note
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.
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.
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.
Inspect protective plugs and damping sleeves for damage.
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.
Pull the brake caliper back and off. Then take the outer brake pad out of the brake caliper.
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.
To avoid damage, do not leave the brake caliper hanging from the brake hose!
Check the wear limit of the brake disc using a suitable tool.
The reference value in millimeters is stamped on the outer edge or on the brake disc pot.
If the brake discs are sticking, carefully tap the bottom of the brake disc pot with a rubber hammer.
New brake pads may only be installed if the minimum thickness of the brake discs (MIN TH) has not been undershot.
Unevenness of the contact face can lead to warping of the brake disc and therefore axial runout!
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!
Mount the brake disc and fasten with fixing screw.
Observe the tightening torque!
The recommended way to do this is to remove the anchor bracket and clamp it in a vise.
Then apply a thin coating of non-conductive, non-metallic anti-squeal paste to the clean contact faces of the caliper anchor bracket.
Push the brake piston right back using the reset tool.
Observe the brake fluid level in the expansion tank when pushing back the pistons. Drain the tank beforehand if necessary.
Thinly coat the contact face (A) of the brake piston with anti-squeal paste.
New brake pads may only be installed if the brake disc is thicker than the minimum brake disc thickness (MIN TH).
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 and fasten with the guide screws.
Observe the tightening torque!
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.
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 brake fluid level in the expansion tank and fill up to the "MAX" marking if necessary.
Only use new brake fluid that has been approved for the vehicle type.
Clean the brake disc after mounting the brake caliper.
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.
Once the repair has been carried out, it is essential to perform a functional check of the brake system.
In this case, please observe the general information on braking in new brake discs and brake pads!