Up to model year 1978 on BMW "518", "520" and "520i" used front disc brakes, rear drum brakes, on the BMW "525" and "528" - front and rear disc brakes. From the 1978 model year, all models were equipped with front and rear disc brakes.
Cooling of the brake discs is provided by air intake at the level of the radiator grille. The parking brake system with cable drive acts on the rear brake shoes. The parking brake system is adjusted on the drive lever in the passenger compartment.
Front wheel brakes
Front wheel brakes with fixed caliper, four-piston, with three nipples for removing air from the system and automatic adjustment of the gaps between the brake pads and the disc.
Brake mechanism brand: ATE 51R.
Piston diameter, mm: 40.
Outer disc diameter, mm: 272±0.2.
Disc thickness, mm: 12.7-0.2.
Minimum disc thickness during operation, mm: 11.7.
Axial runout of the working surface of the disk, no more than, mm:
- when measured on a car: 0.2;
- when measured on a removed disk: 0.05.
Permissible difference in thickness of the working surface of the disk, no more than mm: 0.02.
Permissible disk imbalance, no more than, gf cm: 50.
Brand and type of brake pads: Textar T 260 FF.
Brake pad markings: yellow-green-yellow marks, three grooves.
Minimum brake pad thickness, mm: 7.0.
Since the 1977 model year on cars of the models "525", "528" and the "528i" had new brake pads installed.
Since the 1980 model year, the following front brake specifications have been changed.
Minimum friction lining thickness (when worn out), mm: 3.5.
Minimum brake disc thickness on 535i model vehicles, mm: 24.
Since the 1982 model year, some characteristics of the front wheel brake mechanisms have been changed.
Brand and type of brake pads: Textar T 260/14 MM.
Minimum brake disc thickness on cars of models "518" and "520i", mm: 11.
Rear wheel brakes
BMW "518", "520" and "520i"
The rear wheel brakes are drum-type, with self-centering shoes.
Drum diameter, mm: 250.
Permissible increase in drum diameter after boring and grinding, no more than, mm: 251 (0.5 mm each).
Maximum permissible drum ovality, mm: 0.05.
Permissible drum imbalance, gf cm: 150.
Brand and type of friction linings: Jurid 118, Energit 336.
Brake lining length, mm: 218.
Brake shoe width, mm: 40±0.5.
Minimum friction lining thickness (when worn out), mm: 3.0.
BMW "525", "528"
The rear wheel brake mechanisms are disc brakes with fixed two-piston calipers, with automatic adjustment of the gaps between the pads and the disk. The parking brake mechanism is drum, two-shoe.
Brake mechanism brand: ATE.
Piston diameter, mm: 42.
Outer disc diameter, mm: 272±0.2.
Disc thickness, mm: 9.5-0.2.
Minimum disc thickness during operation, mm: 8.5.
Permissible axial runout of the working surface of the disk, no more than, mm:
- when measured on a car: 0.2;
- when measured on a removed disk: 0.05.
Permissible difference in thickness of the working surface of the disk, no more than, mm: 0.02.
Permissible disk imbalance, no more than, gf cm: 50.
Brand and type of brake pads: Textar T 260 FF.
Brake pad markings: yellow-green-yellow marks, one groove.
Minimum brake pad thickness, mm: 7.0.
Since the 1978 model year, disc brakes with a two-piston caliper from the ATE brand were installed.
Friction lining wear sensors were installed on the brake mechanisms of the left front and right rear wheels.
For BMW "525", "528" and "528i" the thickness of the brake pads is 15±0.6 mm; minimum thickness of friction linings - 2.0 mm; the width of the shoe socket is 44 mm.
Since model year 1980.
Brand and type of brake pads for "528i": Textar T 260.
Minimum thickness of friction linings, mm: 3.5.
The following brake specifications have been changed for the 525i and 528i models since the 1982 model year.
Brand and type of brake pads: Textar E 260/12 MM.
Minimum brake disc thickness, mm: 9.0.
Parking brake system ("525", "528")
Drum diameter, mm: 160.
Friction lining width, mm: 25±0.2.
Friction lining brand: Energit 338 FG.
When the parking brake system is adjusted correctly, the drive lever should move no more than 5-6 teeth of the sector.
Master brake cylinder
Brand:
- "518", "520", "520i": ATE T 51/920;
- "525", "528": ATE T 51/9" E.
Piston diameter, mm:
- "518", "520", "520i": 23,81;
- "525", "528": 22,2.
Clearance between piston and pusher, mm: 0.5.
Test pressure according to ATE company instructions, kg/cm²: 100-20.
The test pressure should not decrease by more than 10% within 1 min.
Brand of brake fluid used: ATE "S" or Castrol Girling (green liquid type B 445).
Since the 1978 model year, the following brands of brake fluid have been used:
- Ate DOT 4 "SL";
- Pentosin Super DOT 4;
- Castrol Disc Brake Fluid DOT 4.
Piston diameter for "525" and "528", mm: 22.2.
Piston diameter for "528i", mm: 23.81.
Piston stroke, mm:
- first circuit: 19;
- second circuit: 13.
Since model year 1980, when tested under a pressure of 100 kg/cm², the drop in test pressure over 2 minutes must not exceed 8%.
Vacuum booster
Brand and type: ATE BRM 18.
Switching pressure, kg/cm²: 20.
Since the 1978 model year, the BMW "525" and "528" were equipped with a vacuum booster of type T 52/225, and the "528i" with a vacuum booster of type T 51/811.
Since the 1982 model year, the BMW "525i" and "528i" were equipped with a DS brand vacuum booster with the following characteristics:
- maximum working pressure, kg/cm²: 130;
- separation pressure, kg/cm²: 5.2-5.7;
- connection pressure, kg/cm²: 3.6-4.1.
Tightening torques of main threaded connections, kgf·m
- Bolt for mounting the caliper to the steering knuckle: 8.0-9.5.
- Brake disc mounting bolt to wheel hub: 6.0-6.7.
- Brake hose tips 1.3-1.6.
- Nut for fastening the vacuum booster to the bracket: 2.2-2.4.
- Bolt for fastening the caliper bracket to the suspension arm: 6.0-6.7.
- Nut securing the master cylinder to the vacuum booster: 1.2-1.5.
- Connecting bolt of brake caliper halves: front wheel: 4.4-5.5; rear wheel: 2.2.
- Wheel mounting nut: 8.0-9.0.
- Since 1982 model year
- Bolt for fastening the brake disc to the outer end of the wheel hub: M6: 0.4-0.5; M8: 3.0-3.3.
- Bolt for fastening the caliper to the steering knuckle: no more than 12.3.
- Nut securing the master cylinder to the vacuum booster: 1.6-2.5.