Always ensure that the vehicle is securely chocked on level ground before releasing the parking brake. Cage the spring brake or use a minimum hold off pressure of 90 psi (6 bar).
Operational checks should be carried out annually or at every pad replacement. It is important to check the brake adjuster is functioning correctly and that the caliper slides smoothly over its full range of travel.
Ensure that service brake and parking brake are in the released condition – always ensure the vehicle is securely chocked before releasing the parking brake. Push and pull caliper 3 times in an axial direction to assess the running clearance between pads and disc. If the caliper does not move then check the condition of the guide sleeve bushes. Remove the adjuster cap and fit new pads. Set the clearance by turning the adjuster anti-clockwise with a suitable 10 mm ring spanner or socket wrench, and then turn clockwise until 1.3 mm running clearance has been achieved, measured between the tappet heads & inboard pad, ensuring there is no clearance at the outboard pad.
! Never exceed a maximum torque of 25 Nm in either direction, and never use power tools.
Note: When turning the adjuster anti-clockwise a noticeable clicking should be heard & felt.
Apply the brakes 20 times with pressure of 2-3 bar. Measure the clearance between each tappet head and the inboard pad backplate – this should be measured over the whole surface of both tappet heads simultaneously using
two feeler gauges at least 220 mm long. The running clearance between each tappet head and inboard pad backplate must measure between 0.6 - 1.2 mm. If the difference between the running clearance at each tappet head is more than 0.25 mm then check the condition of the guide sleeve bushes.
If the running clearance is bigger than 1.2 mm then the adjuster must be checked as follows;
• Turn the adjuster anti-clockwise by 3 clicks to increase the running clearance.
• Position a ring spanner or socket wrench onto the adjuster as a visual aid, as shown, ensuring there is sufficient clearance for it to move freely.
• Apply the brake 5 to 10 times (with 2-3 bar pressure) and the ring spanner should turn clockwise in small increments (as viewed from the air chamber side). Note that as the number of applications increases then incremental movement of the spanner will decrease.
• If the ring spanner does not turn, or turns only with the first application, or turns forward and backward with every application, then there is a problem and the caliper must be replaced.
If the running clearance is smaller than 0.6 mm then the caliper must be checked as follows;
• Remove the air chamber and check that the lever is in contact against the caliper housing (see arrow “L”).
• Remove the brake pads and if necessary, remove dirt from the brake pads, carrier & caliper;
• Check the brake pads for wear from the tappet heads. If necessary replace the brake pads.
• Check for wear of the pad contact areas of the carrier and if necessary replace the carrier.
• Check the brake disc for wear or damage and if necessary replace the disc.
• Check caliper slides smoothly over its full range of travel (see Caliper Sliding check).
• Refit the brake pads and the air chamber. Repeat the adjuster function check. If the running clearance is still smaller than 0.6 mm then the caliper must be replaced.
! If the running clearance is too big there is a risk of reduced brake performance and brake failure.
! If the running clearance is too small there is a risk of overheating and subsequent damage.
Note: opening the caliper or removing the adjuster will invalidate the warranty.