If the automatic adjustment arm is not maintained on time, brake failure can be very dangerous

First of all, it should be noted that the automatic adjusting arms used on trucks are technically mature and have been widely used in developed countries in Europe and America for many years, with no obvious design flaws. In terms of the technology of the product, automatic adjusting arms have many advantages, as they can constantly adjust the ideal gap between the brake shoes and the wheel hub while driving, ensuring good braking performance and avoiding the unevenness and hassle of manual adjustment.

However, recently I discovered a very serious safety issue. There is a 6X4 tractor that's one year and five months old, and the driver reported that the brakes were not performing well. When asked about it at the time, it seemed a bit suspicious. For a truck that's just over a year old, the main vehicle is equipped with WABCO brake pumps and valves, Fangsheng rear axle, a certain brand of automatic adjustment arm, plus WABCO four-channel ABS, and the trailer has a 12-ton BPW axle, also with WABCO four-channel ABS. With this configuration, how could the brakes perform poorly in such a short time? Reluctantly, a detailed inspection revealed that the two axles on the main vehicle had two wheel hubs with 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 brake is pressed, the brake shoes cannot expand forcefully 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 is designed with a manual adjustment function. When we manually adjust the brakes, after a few uses on the road, the braking effect returns to its original state. Further inspection revealed that the adjuster arm latch cannot actually secure, causing the brakes to automatically revert to the failed state. This issue is present in other vehicles too, and several friends have told me that within two years, their vehicles basically switched entirely to the old manual adjustment. So here's the problem

First, many truck drivers blindly trust automatic adjusting arms, treating them like a magic solution. After all, the mandatory standard for automatic adjusting arms hasn’t been in effect for long, and truck drivers haven't had much exposure to this new component, lacking deeper understanding. Additionally, manufacturers don't provide enough product explanations or usage guidance. Once we truck drivers trust them, we rarely pay attention or check them, not knowing when they might completely fail, and never imagining they could fail entirely in just over a year. When vehicles drive on slippery roads, unbalanced braking can easily cause skidding accidents (even the best ABS can't help much, as ABS isn't万能 in certain circumstances). Worse, in emergencies, the lack of braking force makes it impossible to stop, leading to serious accidents.
 

Second, why does a key component that is technologically mature have such a short service life? Why can foreign products be widely used without problems? This inevitably raises doubts about product quality. In terms of the technical characteristics of the automatic adjuster arm, it uses a preset brake clearance value. When the brake pads exceed the limit during use, the automatic adjuster arm drives the internal one-way clutch to reduce the clearance by one notch when returning after braking, keeping the brake clearance within the normal range. After each automatic adjustment, it needs a latch to lock it in place, just like a manual adjuster arm. However, we have found that failed adjuster arms cannot lock the adjusted clearance. Even after manual adjustment, the clearance returns to the pre-adjusted state after just a few brake applications. I am not a professional, so I cannot provide specific technical data, only speculate based on my own experience. Previously, one of my 6×4 tractors had the same issue, and within two years, I replaced all automatic adjuster arms with regular manual ones because automatic adjuster arms felt short-lived and unpredictable. The purchase cost was also significantly higher; manual ones cost a few tens of yuan each, while automatic arms cost over 300 yuan. The damaged automatic adjusters we've found are basically just over a year old. Personally, I think the design and technical specifications are probably fine. The key issue is the material used in manufacturing; good materials naturally last longer and shouldn't fail within just over a year, yet we noticed many failures within two years. Of course, such products must have undergone extensive testing before market release, with specific requirements for service frequency. Since each brake application engages almost all internal parts of the adjuster, it is linked to how many times the part can be used (for example, tens of thousands of brake applications), which places strict demands on the material of every component of the adjuster.

Thirdly, some card owners said that they've been using it for two or three years and it's been fine. That's true, there are still many card owners on the market who haven't noticed any issues with this product, which comes down to a few reasons. Firstly, the driving conditions vary greatly. Vehicles running on flat highways brake less frequently, so naturally, the wear during use is much lower, making the lifespan seem longer. Vehicles driving on more complex roads or in hilly areas, which brake more often, are more likely to encounter problems.

So when manufacturers consider choosing product materials, they can't just base the lifespan on usage frequency under the best conditions. Of course, these products also come with a warranty (the manufacturer provides 18 months). But I think this year-and-a-half warranty is not ideal because vehicles are used in very different conditions. Vehicles regularly driving in mountains or on rough roads brake more frequently, so problems are more likely within 18 months. Vehicles on plains or highways brake less frequently and may not have issues for two to three years.

There are also national quality standards that must comply with ISO/TS16949:2002. But our country is vast, with widely varying terrain, so some standards differ significantly from reality. Considering the problems identified so far, it seems this automatic adjustment arm should be classified as a "wearable" vehicle maintenance part. However, since it concerns such a critical component for life safety, manufacturers must not compromise quality for profit and operate at the edge of regulations.

Sincere Recommendation

Finally, I suggest manufacturers remember that brakes are serious business as they affect countless lives and family happiness, so they must not be taken lightly! The lifespan should not be designed based on the warranty period, nor should product quality be measured by standards that lack practical foundation. Products should clearly indicate usage limits and reasonably explain performance so end users understand proper maintenance and inspection, ensuring vehicles remain in proper working condition.

I also strongly recommend that truck OEMs strictly control the quality of purchased parts, as the poor quality of one brand's component can ruin your reputation.

Additionally, I strongly advise drivers to frequently monitor and check their brakes, because you never know when your braking power may suddenly decrease. There are serious safety risks, and staying safe is the quickest way home.