Brake drum is the friction couple of drum brake, in addition to the strength and stiffness required as a component, there should be as high and stable friction coefficient as possible, and appropriate wear resistance, heat resistance, heat dissipation and heat capacity.

Problems and solutions of brake drum

1. Uniform excessive wear

The brake drum is quickly and evenly worn due to the large brake resistance, brake imbalance and dust and impurities entering the series. At this point in the brake drum edge will form a very obvious step ring.

2. Unilateral abnormal wear

Sometimes it is found that the brake drum inner surface, one side has obvious wear marks, while the other side has no obvious wear marks.

This is caused by the different centers of brake drum and brake. Further analysis shows that since brake drum and hub are rigidly connected and rotate coaxially, if there is no abnormal phenomenon, the possibility of eccentric rotation of brake drum and hub at the same time is small.

Therefore, more consideration should be given to the installation accuracy of brake shoes. It is necessary to inspect series parts such as brake bottom plate, brake support plate and brake shoe pin one by one.

3. Uniform thermal crack

Due to the long time down the slope of the heavy car, brake drum heat capacity is insufficient and cause the formation of uniform and fine turtle cracks on the friction surface, turtle cracks will continue to spread, lengthen, deepen.

When the turtle crack length increases to 30 ~ 40mm, it needs to be replaced in time, otherwise it is easy to cause serious faults such as brake drum cracking, which will affect the normal use of the vehicle.

4. Local hot (black) spots

When the brake drum is not evenly heated, local heat (black) spots may occur. Some are neatly covered on the friction surface of the brake drum, forming a uniform parallel ring, while some appear in larger local areas or form a uniform distribution of small round spots.

This is mainly due to the material and structure of the brake drum errors caused by the uneven wear, when the more obvious spots need to replace the brake drum in time.

5. Brake drum pull slot

Pulling groove refers to the circle working face in the brake drum to form a deeper notch or groove and other depression, the depth is greater than 2.5 mm, the width is greater than 0.8 mm, this is due to friction plate abnormal wear resulting in the rivet exposed, rivets and other sharp objects in the brake drum circular working face to form a pulling groove. The brake drum and friction plate need to be replaced at the same time.

6. Brake drums turn blue

The circumferential working surface of the brake drum is blue, and the brake drum and brake are likely to have been damaged or deformed. Because the brake drum turns blue, it generates extremely high temperatures during operation.

At this time, the relevant parts need to be carefully inspected and analyzed, and the failed parts need to be completely replaced.

Brake drums fall out

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

Brake drum falling bottom refers to the brake drum circular working part (cylinder) and flange part (disk) off, resulting in brake failure, the main reason is due to the brake drum production process of the structure and material improper factors.

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. Hub grease contamination

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 working friction pair formed by the inner surface of the brake drum and friction plate has been broken, which is easy to cause safety failure of the whole vehicle. Therefore, it is necessary to replace the brake drum immediately.