BRAKES 22 REAR DRUM BRAKES CONSTRUCTION AND WORKING This brake is designed for use on rear wheels and is equally efficient in both forward and reverse direction of movement. A mechanical lever mechanism is incorporated for normal hand brake operation. The feature of this brake is that the brake shoe adjustment takes place automatically when the service brake is applied. The leading and trailing shoes are connected at one end by a two-piston wheel cylinder and an adjuster assembly. The adjuster assembly consists of a male and female pushrod with an adjuster nut operated by a pawl. Coupled on the trailing shoe is a hand brake lever which pivots on a pin at the wheel cylinder end of the shoe. A spring dowel fitted at the leading shoe provides a pivot for the pawl lever, which is retained in position by a spring hooked on to the web. The hand brake cable passes through a hole in the back plate, and the slotted cable end fits in the end of the hand brake lever. When the handbrake is applied, the cable pulls the lever and this movement is transferred via the adjuster assembly to the shoes, which moves outwards onto the drum. When the foot brake is operated, both the shoes are pushed on to the drum by the wheel cylinder pistons. As the shoe linings wear, the outward movement of the shoes exceeds a predetermined amount and the pawl pivots on the spring dowel to rotate the adjuster nut. This action lengthens the adjuster assembly sufficiently to reduce the clearance between the brake shoes and drum to the desired minimum. The adjustment is repeated, whenever necessary, according to the rate of lining wear. BRAKE MAINTENANCE Note: The rear brake shoes have to be replaced insets only. If you are replacing brake shoes on left side brakes then the brake shoes on right side brakes should also be replaced. To maintain the efficiency of the brake system, preventive maintenance is essential and the following recommendations should be observed at the intervals stated. BRAKE ADJUSTMENT As it is an auto adjust brakes, brake adjustment is not required. 1. Every 10,000 kms check the lining for wear through the inspection hole provided in the back plate, removing the grommet. The linings should not be allowed to wear below 1mm lining thickness. 2. Every 20,000 kms clean the back plate and lubricate the tips of the shoe platforms with graphite grease and the moving parts of the adjuster with mineral grease. Keep the grease away from the shoe lining sand all hydraulic parts. 3. The wheel cylinder should be overhauled once in 40,000 kms or 18 months whichever is earlier. MAJOR OVERHAUL It is essential that the shoe linings are inspected at regular intervals to prevent the drums being permanently damaged and subsequently making drum removal extremely difficult. 1. Choke the front wheels, release the hand brake and jack up the rear wheels. Support the rear axle with horse stands. 2. Slacken off the hand brake cable.
RkJQdWJsaXNoZXIy MTIwNTUz