Before model year 1978 on BMW «518», «520» And «520i» front disc service brakes were used, rear drum brakes, on BMW «525» And «528» - front and rear service brakes - disc. Starting with the 1978 model year, all models had disc front and rear service brakes.
The brake discs are cooled by air intake at the level of the radiator lining. The cable-operated parking brake system acts on the rear brake pads. The parking brake system is adjusted on the drive lever in the passenger compartment.
Front wheel brakes
Brake mechanisms of the front wheels with a fixed caliper, four-piston, with three fittings for removing air from the system and automatic adjustment of the gaps between the brake pads and the disc.
Brake brand: ATE 51R.
Piston diameter, mm: 40.
Outer diameter of the disk, mm: 272±0.2.
Disc thickness, mm: 12.7-0.2.
The minimum thickness of the disk during operation, mm: 11.7.
Axial runout of the working surface of the disc, no more than, mm:
- when measured on a car: 0.2;
- when measured on a removed disk: 0.05.
Permissible difference in the thickness of the working surface of the disk, no more. mm: 0.02.
Permissible disc imbalance, not more than, gf cm: 50.
Brand and type of brake pads: Textar T 260 FF.
Brake pad marking: yellow-green-yellow marks, three grooves.
Minimum brake shoe thickness, mm: 7.0.
From model year 1977 on model cars «525», «528» And «528i» new brake pads were installed.
For model year 1980, the following front wheel brake specifications have been changed.
Minimum friction lining thickness (when worn), mm: 3.5.
The minimum thickness of the brake disc on the cars of the model «535i», mm: 24.
Since the 1982 model year, some characteristics of the front wheel brakes have been changed.
Brand and type of brake pads: Textar T 260/14 MM.
Minimum brake disc thickness on car models «518» And «520i», mm: 11.
Rear wheel brakes
BMW «518», «520» And «520i»
The rear wheel brakes are drum brakes with self-centering pads.
Drum diameter, mm: 250.
Permissible increase in drum diameter after boring and grinding, no more than, mm: 251 (0.5 mm).
Maximum permissible ovality of the drum, mm: 0.05.
Permissible imbalance of the drum, 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), mm: 3.0.
BMW «525», «528»
Brake mechanisms of the rear wheels are disc, with fixed two-piston calipers, with automatic adjustment of the gaps between the pads and the disc. The parking brake mechanism is drum, two-shoe.
Brake brand: ATE.
Piston diameter, mm: 42.
Outer diameter of the disk, mm: 272±0.2.
Disc thickness, mm: 9.5-0.2.
The minimum thickness of the disc during operation, mm: 8.5.
Permissible axial runout of the disk working surface, not more than, mm:
- when measured on a car: 0.2;
- when measured on a removed disk: 0.05.
Permissible difference in the thickness of the working surface of the disk, not more than, mm: 0.02.
Permissible disc imbalance, not more than, gf cm: 50.
Brand and type of brake pads: Textar T 260 FF.
Brake pad marking: yellow-green-yellow marks, one groove.
Minimum brake shoe thickness, mm: 7.0.
Since the 1978 model year, disc brakes with a two-piston ATE brand caliper have been installed.
Friction lining wear sensors were installed on the brake mechanisms of the left front and rear right wheels.
For BMW «525», «528» And «528i» the thickness of the brake pads is 15±0.6 mm; the minimum thickness of friction linings is 2.0 mm; shoe socket width - 44 mm.
From model year 1980.
Make and type of brake pads «528i»: Textar T 260.
Minimum thickness of friction linings, mm: 3.5.
Since the 1982 model year, the following brake characteristics have been changed on model cars «525i» And «528i».
Brand and type of brake pads: Textar E 260/12 MM.
The minimum thickness of the brake disc, 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.
With a properly adjusted parking brake system, the drive lever should move no more than 5-6 sector teeth.
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.
Gap between piston and pusher, mm: 0.5.
Test pressure according to ATE instructions, kg/cm2: 100-20.
The test pressure shall not decrease by more than 10% within 1 min.
Brake Fluid Brand: ATE «S» or Castrol Girling (green liquid type B 445).
Since model year 1978, the following grades of brake fluid have been used:
- Ate DOT 4 «SL»;
- Pentosin Super DOT 4;
- Castrol Disc Brake Fluid DOT 4.
Piston diameter «525» And «528», mm: 22.2.
Piston diameter «528i», mm: 23.81.
Piston stroke, mm:
- primary circuit: 19;
- second circuit: 13.
From model year 1980, when tested under a pressure of 100 kg/cm2, the drop in test pressure in 2 minutes shall not exceed 8%.
Vacuum booster
Make and type: ATE BRM 18.
Switching pressure, kg/cm2: 20.
From model year 1978 on BMW «525» And «528» a vacuum booster type T 52/225 was installed, and on «528i» - type T 51/811.
From model year 1982 on BMW «525i» And «528i» a DS brand vacuum booster was installed 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 the main threaded connections, kgf·m
- Bolt of fastening of a support to a rotary fist: 8,0-9,5.
- Bolt for fastening the brake disc to the wheel hub: 6.0-6.7.
- Tips of brake hoses 1,3-1,6.
- Nut for fastening the vacuum booster to the bracket: 2.2-2.4.
- Bolt of fastening of an arm of a support to the suspension arm: 6,0-6,7.
- Nut of fastening of the main cylinder to the vacuum amplifier: 1,2-1,5.
- Connecting bolt halves of the brake caliper: front wheel: 4.4-5.5; rear wheel: 2.2.
- Wheel nut: 8.0-9.0.
- From model year 1982
- 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 of fastening of a support to a rotary fist: no more than 12,3.
- Nut of fastening of the main cylinder to the vacuum amplifier: 1,6-2,5.