Disc and Drum Brake Inspection and Maintenance
Disc Brake Inspection and Maintenance
1. Operation Check: Verify disc brake operation by observing the pedal displacement and caliper movement. If the caliper does not move correctly, remove it and repair it. Ensure there are no fluid leaks in the actuator or the hose connection. Check the condition of the disc and pads. Replace them if they are defective.
2. Brake Pad Thickness: The brake pad thickness should be superior to 2mm. When some pads are defective, all pads on the same axle must be replaced.
3. Replacing Brake Pads: When replacing brake pads, the increased thickness of the new pads requires moving the plungers of the operating cylinders. This can be done with the help of a jack.
4. Irregular Wear: If irregular wear is observed on the pads of a single wheel, check that the piston in the cylinder is not jammed and that the caliper slides correctly. Irregular wear can indicate a seized piston. Dismantle the cylinder for cleaning if necessary. Replace the cylinder if you find any anomalies, such as scratches or abrasions.
5. Piston Removal and Assembly: Piston removal is facilitated by using hydraulic pressure. Carefully actuate the brake pedal or use compressed air introduced through the fluid inlet orifice. Ensure the piston does not hit anything upon exit. During assembly, lubricate the cylinder and piston surfaces with abundant brake fluid. After assembly, check for leaks by immersing the assembly in a pot of water and applying air through the fluid inlet at a pressure less than 2 bar. A continuous rise of bubbles indicates leaks. In this case, disassemble again and replace the piston ring or seal.
6. Brake Disc Inspection: Replace the brake disc when wear exceeds 10% of its thickness, which can be checked with a micrometer. Check for warping by positioning the disc on a dial gauge probe and rotating it by hand. Deviations should not exceed 0.1mm. If they do, replace the disc and install new pads.
Drum Brake Inspection and Maintenance
1. Initial Inspection: After removing the brake drum and before further dismantling, inspect the condition of the components, their mounting position, and the degree of wear. Ensure the drum does not have excessive wear or scratches on its surface. Otherwise, it should be rectified or replaced.
2. Ovality Check: The ovality of the circular friction area must be less than 0.1mm.
3. Brake Shoe Inspection: Check that the brake shoes are not distorted or have any cracks. If they do, they must be replaced. Ensure the recoil springs are efficient. Replace them whenever the brake shoes are changed.
4. Brake Lining Condition: The brake linings must not be dirty or oily. If they are, replace the brake pads or shoes. Replacement is necessary when the lining thickness is less than 2mm.
5. Cylinder Inspection: Check that the cylinders have no fluid leaks before proceeding with the revision and disassembly.
6. Brake Shoe Adjustment: After completing the brake assembly, adjust the brake shoes. In the conventional type, lift the wheel and act on the adjustment nut of each shoe, turning the key down until the wheel locks. Then, loosen it slightly so that the wheel rotates freely without friction.