1. Uniform excessive wear

Due to a series of reasons such as large brake resistance, brake imbalance and dust impurities into the brake drum is fast and uniform wear. This will form a very visible step ring on the edge of the brake drum.

2. Unilateral abnormal wear

It is sometimes found that there are obvious wear marks on one side of the inner circle of the brake drum, while there are no obvious wear marks on the other side.

This is due to the brake drum and brake different heart caused, further analysis, because the brake drum and hub is rigid connection coaxial rotation, if there is no abnormal phenomenon, the brake drum and hub at the same time the possibility of eccentric rotation is small.

So we need to consider more about the accuracy of the brake shoe installation. We need to check the brake bottom plate, brake pallet, brake shoe pin and other series of parts one by one.

3. Uniform thermal crack

Due to the heavy vehicle downhill for a long time, the brake drum heat capacity is insufficient and leads to the formation of uniform and detailed turtle cracks on the friction surface, and the turtle cracks will continue to spread, lengthen and deepen. When the crack length of the turtle grows to 30 ~ 40mm, it needs to be replaced in time, otherwise it is easy to form serious faults such as crack of the brake drum, which will affect the normal use of the vehicle.

4. Local hot (black) spots

When the brake drum is heated unevenly, it may produce local hot (black) spots. Some of them cover the entire friction surface of the brake drum neatly, forming a uniform parallel ring, and some will appear or form small circular spots with uniform distribution in a large local area.

This is mainly due to the uneven wear caused by the material and structure error of the brake drum. When the above spots appear more obvious, the brake drum needs to be replaced in time.

5. Brake drum and pull groove

Groove refers to the formation of deep marks or grooves in the circumscribed working face of the brake drum. When the depth is greater than 2.5 mm and the width is greater than 0.8 mm, it is due to the abnormal wear of the friction plate leading to rivets, and sharp objects such as rivets form grooves in the circumscribed working face of the brake drum. At this time, the brake drum and friction plate need to be replaced at the same time.

6. Brake drum blue

The inner circumscribed working surface of the brake drum is blue. At this time, the brake drum and the brake are likely to have been damaged or deformed. The blue color of the brake drum proves that it produces extremely high temperature during its operation. At this time, it is necessary to carry out a careful inspection and analysis of the relevant parts, and thoroughly replace the failed parts.

7. Brake drum is bottomed out

Brake drum and wheel hub are connected together by a ring of flange bolts (also wheel bolts), the brake force generated by the brake drum is transmitted to the wheel hub through the flange bolts to limit the rotation of the wheel.

The bottom of the brake drum refers to the working part of the circumference of the brake drum (cylinder) and the flange part (disc) off, resulting in brake failure, the main reason is still due to the improper structure and material factors in the manufacturing process of the brake drum.

8. Brake drum bolt hole wear

Brake drum bolt hole wear, usually because the flange bolts (wheel bolt) not fully tighten, relative wheel brake drum radial and axial occur relatively dynamic impact, lead to abnormal wear of brake drum bolt hole deformation, wheel bolt, wheel hub and related parts and components will be irreversible serious fault occurs, the need for related spare parts for all replacement.

9. Oil pollution of wheel hub

When the wheel hub oil seal failure, lubricating oil/grease was dumped the circumference of a circle on the working plane to the brake drum, face serious pollution, and still not handled in time, the lubricating oil/grease will further infiltration within the brake drum circumferential face, it's hard to reverse damage, because oil/fat actually has penetrated into the brake drum.

At this time, the internal surface of the brake drum and the working friction pair formed by the friction plate have been broken, and the safety failure of the vehicle is easy to occur, so the brake drum needs to be replaced immediately.