Parking Brake System: Adjustments

Test Specifications
- When 1st tooth is engaged, no braking effect should be applied at all.
- The wheel rotational force compared to the wheel on the opposite side (measured on the roller test rig) must not exceed the higher value by more than max. 30%. Adjustment is necessary in case of greater brake-force difference.
- It should be possible to hold vehicle with handbrake.
- Handbrake must be adjusted if handbrake-lever travel is greater than ten teeth.

NOTE:
- Handbrake can only be adjusted correctly if handbrake cables and all moving parts of handbrake move easily and function correctly.
- Basic handbrake adjustment is necessary:
After replacing brake shoes
After replacing brake drums/brake disks
After resetting slack-control device
In case of excessive handbrake-lever travel (ten teeth)





- Lift out dust cover.





- Unscrew locknut using special tool 34 1 030 and loose cable completely.

Installation Note: Lock adjusting nut with locknut.

1. Basic setting
1.1 Drum Brake

NOTE:
- If necessary, fit wheels (brake drums must be secured)
- Tightening torque, refer to Steering and Suspension.

- Operate brake pedal until slack-control sound (soft click) is no longer audible.
- (Slack-control operation can also be observed through a wheel-bolt bore).

1.2 Disc Brake (Duo-Servo Handbrake)
- Unscrew and remove one wheel bolt from each rear wheel.





- Turn wheel until tapped bore is positioned approx. 65° behind a vertical line at top (seen in forward driving direction).

Installation Note:
- Fit wheel nut and tighten down.
- Tightening torque, refer to Steering and Suspension.





- Turn adjusting screw using a screwdriver until wheel or brake disk can no longer be turned.
- Left wheel is blocked in direction (a), right wheel in direction (b).
- Loosen adjusting screw 18 catches (M3: 8 catches) afterwards.

2. Adjustment Of Bowden Cables
2.1 Manually
- Pull handbrake lever up six teeth (M3: four teeth) and turn adjusting nuts until it is just possible to still turn rear wheels.
- Release handbrake lever; it must be possible to turn wheels easily.
- Switch on ignition, indicator lamp must be switched off when handbrake is released
1st tooth: No braking effect.
Indicator light could be on.
2nd tooth: Braking effect must begin (not applicable for M3).
Indicator lamp must be lit: if necessary, adjust switch contact on handbrake lever.
2.2 On Dynamometer
- Tooth 0: (handbrake lever released) wheel peripheral force at idling speed in vehicles
a) without limited slip differential less than 150 N
b) with limited slip differential less than 200 N
- 1st tooth:
No braking effect.
Indicator light could be on.
- 2nd tooth:
Adjust handbrake cables until braking action takes effect (does not apply to M3).
Checking Braking-Force Difference With:
- Duo-servo handbrake on 4th ratchet tooth
- Drum brake on 7th ratchet tooth.
The braking force difference between left and right may be max. 50 N.
If difference is greater, handbrake cable on side with higher braking force must be slackened slightly.
- M3
Pull up handbrake lever by 3 teeth.
Adjust handbrake cables on left/right until brake force indicator shows that 600N + 50N have been reached.

3. Braking In Specification For Duo-Servo Handbrake
- The following braking-in procedures are applicable in case of insufficient braking effect or after replacing brake disks and/or brake shoes.
- With vehicle moving at approx. 40 km/h, pull up handbrake lever until braking of vehicle is noticed.
- Then pull up handbrake lever into next catch and drive approx. 400 m in this position. (A basic requirement is that handbrake is adjusted uniformly.)

NOTE:
- Handbrake is completely independent of service brake and consequently is only subjected to limited wear.
- In the course of time, dirt and corrosion will quite often cause braking effect of handbrake to diminish.