If the automatic adjusting arm is not maintained in time, brake failure can be very dangerous.

First of all, it should be noted that the automatic adjustment arms currently used on trucks are technically mature and have been widely used in developed countries in Europe and the United States for many years, without any obvious design flaws. In terms of technological content, the automatic adjustment arms have many advantages: they can continuously adjust the optimal gap between the brake shoes and the wheel hub during driving, maintaining good braking performance, while also avoiding the unevenness and hassle associated with manual adjustments.

However, I recently discovered a very serious safety hazard. There is a 6X4 tractor that is one year and five months old, and the driver reported that the vehicle's braking performance was unsatisfactory. When I inquired at the time, I felt something was off. The truck is over a year old, with the tractor equipped with WABCO brake pumps and valves throughout, Fangsheng rear axles, an automatic adjustment arm of a certain brand, and WABCO four-channel ABS. The trailer has a 12-ton BPW axle, also equipped with WABCO four-channel ABS. With such a configuration, how could the braking performance be poor in such a short period? Reluctantly, I conducted a detailed inspection and found that two wheel hubs on the second and third axles of the tractor had no brakes at all.
 

After further inspection, it was found that the gap between the brake shoes and the hub was very large. When the brakes were applied, the brake shoes could not expand effectively to create enough friction with the hub. This indicates that the automatic adjuster arm has failed and completely lost its automatic adjustment function. A more serious problem is that the automatic adjuster arm itself is designed with a manual adjustment function. When we manually adjusted the brakes, after driving and using the brakes a few times, we found that the braking effect returned to its original state. Upon further inspection, it was discovered that the lock of the adjustment arm could not secure properly, causing the brakes to automatically revert to a failed state. This situation also exists in other vehicles, and several car owners have even told me that within two years, they basically all replaced them with the old-style manual adjustments. 

So, here comes the question.

1. Many truck drivers blindly trust the automatic adjusting arm and treat it as a magic solution. After all, the mandatory implementation of the automatic adjusting arm is still relatively new, and truck drivers have limited experience with this new component, lacking a deeper understanding of it. In addition, manufacturers also provide insufficient product explanations and usage instructions. As a result, once drivers highly trust it, they rarely monitor or inspect it, not knowing when it might fail completely, and they can't even imagine that it could fail entirely in just over a year. When the vehicle is driven on slippery roads, uneven braking force can easily cause skidding accidents (even the best ABS won't help, as ABS is not a cure-all in certain conditions). More seriously, in an emergency, due to the lack of braking force, the vehicle may not be able to stop at all, leading to serious accidents.
 

Second, why does a key component with inherently mature technology have such a short service life? Why can foreign products be widely used without issues? This inevitably raises suspicions about product quality. From the technical characteristics of the automatic adjusting arm, it works by using a preset brake clearance value. During the use of the vehicle's brake pads, when the clearance exceeds the limit, the automatic adjusting arm will drive the internal one-way clutch mechanism to reduce the clearance by one step when returning after braking, keeping the brake clearance within the normal range. After each automatic adjustment, like a manual adjusting arm, it needs a locking mechanism to secure it, but currently we have found that all failed or damaged adjusting arms cannot lock the adjusted clearance position. Even after manual adjustment, after a few brake applications, the clearance returns to its pre-adjusted state.

I am not a professional, so I cannot provide specific technical data and can only speculate on the problem based on my own experience. Previously, one of my 6×4 tractors had the same issue, and within two years, all the automatic adjustment arms were replaced with regular manual adjustment arms. I felt that the automatic adjustment arms did not have a long service life and were unpredictable, while their purchase price was several times that of the original manual adjustment arms. Generally, manual adjustment arms cost a few dozen yuan each, but automatic adjustment arms cost more than 300 yuan. The damaged automatic adjustment arms we have found so far mostly lasted just over a year. Personally, I think the product design and technical features should be fine. The key issue is the material used in manufacturing. High-quality components certainly have a longer service life and would not gradually fail within just over a year (we have found many cases within two years). Of course, this type of product would have undergone extensive testing before research and release to the market and should have specific requirements for usage frequency and lifespan. Every time the brake is pressed, the internal mechanisms of the adjustment arm almost all operate simultaneously, which involves how many times the component is allowed to be used (for example, tens of thousands of brake presses). These requirements place strict demands on the materials of all parts of the adjustment arm.

Third, some truck drivers have said that they have been using it for two or three years and it has always worked well. That's correct—currently, there are still many truck drivers in the market who haven't noticed any problems with this product. This involves several factors. First, the driving conditions of vehicles vary greatly. Vehicles that run on flat highways have a low braking frequency, so, relatively speaking, the wear during use is much less, and of course, the perceived lifespan feels longer. Vehicles that operate in more complex road conditions or in hilly areas, where braking is more frequent, are more likely to encounter problems.

Therefore, when manufacturers consider the selection of product materials, they cannot determine the service life solely based on usage frequency under the best conditions. Of course, such products do have a warranty period (the manufacturer provides 18 months). However, I think this one-and-a-half-year warranty is not ideal because vehicle usage varies greatly. Vehicles frequently used in mountainous areas or on roads experience high braking frequency, which increases the likelihood of problems occurring within 18 months. Vehicles used on plains or highways have lower braking frequency and may continue to function properly for two to three years without issues. 

There are also national quality standards that must be certified through ISO/TS16949:2002. However, our country is vast with highly varied terrain, and some standards differ significantly from practical conditions. Based on the problems identified so far, it seems that this automatic adjustment arm should be categorized as a vehicle maintenance 'wear-and-tear part.' However, since this concerns one of the most critical components related to life safety, manufacturers must never allow quality to skirt the boundaries of regulations for the sake of profit!

Solemn Recommendation

Finally, I strongly advise manufacturers: brakes are no small matter, as they concern countless lives and the happiness of countless families. Carelessness is absolutely unacceptable! The design of service life must never be based on the warranty period, nor should standards set without practical basis be used to measure product quality. Whenever possible, indicate the product's service life during promotion, provide a reasonable and scientific introduction to the product's performance, and ensure that end-users have correct knowledge for proper maintenance and inspection, keeping vehicles always in normal working condition.

Here, I also strongly urge truck manufacturers to strictly control the quality of components when purchasing parts. Do not let the quality issues of a single brand’s components damage your brand’s reputation.

At the same time, I strongly advise truck drivers to frequently pay attention and check their vehicles, as you never know when your brakes might lose the braking force of several hubs. Serious safety hazards exist, and staying safe is the quickest way to get home.