Wheel cylinders
1. Check the cleanliness of the working surfaces of the cylinder, pistons and thrust rings.
2. The surfaces must be completely smooth, without roughness, to prevent fluid leakage and premature wear of seals and pistons.
3. Eliminate defects on the cylinder mirror by grinding or polishing. However, increasing the internal diameter of the cylinder is not allowed.
4. Check the condition of the stop screw 3 (see Fig. Wheel cylinder parts), springs 6, cup support 7 and crackers 5. If necessary, replace damaged parts with new ones.
5. Replace the seals 8 with new ones. Check the condition of the protective caps 10 and replace them if necessary.
Pads
1. Check the pads carefully for damage or deformation.
2. Check the elasticity of the tension springs, both upper and lower; replace them with new ones if necessary.
3. The springs must not have residual deformations when stretched with a force of 343 N (35 kgf) for the lower springs and 411 N (42 kgf) for the upper springs.
4. Check the cleanliness of the linings; if dirt or traces of grease are found, thoroughly clean the linings with a wire brush and wash with white spirit, also check for grease or oil leaks inside the drum; please fix the problems.
5. Replace the pads with new ones if the thickness of the linings has become less than 1.5–2 mm.
Brake drums
1. Inspect them. If there are deep scratches or excessive ovality on the working surface, ream the drums on the machine.
2. Then use a lathe to grind the drums with fine-grained abrasive blocks. This increases the durability of the pads and improves the uniformity and effectiveness of braking.
3. The maximum allowable increase in the nominal drum diameter (250 mm) after boring and grinding is 1 mm. The limits of this tolerance must be strictly observed, otherwise the strength of the drum and the braking efficiency are impaired.