It's risky if the automatic adjustment arm isn't maintained properly and the brakes fail

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 without obvious design flaws. In terms of technological content, automatic adjusting arms have many advantages, as they can constantly adjust the optimal gap between brake shoes and the wheel hub during driving, maintaining good braking performance while avoiding the drawbacks and hassle of manual adjustments.

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 weren't working well. When I asked about it at the time, it seemed a bit suspicious. For a truck that's just over a year old, the main vehicle has a full WABCO brake pump 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 kind of configuration, how could the brakes be ineffective in such a short time? Reluctantly, I conducted a thorough inspection and found that the two hubs on the second and third axles of the main vehicle 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 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 issue is that the automatic adjuster arm is designed with a manual adjustment function. When we manually adjust the brakes, during driving, after just a few uses of the brake, the braking effect returns to its original state. Further inspection revealed that the original adjuster arm latch cannot hold, causing the brakes to automatically revert to a failed state. This problem also exists in other vehicles, and several fellow drivers have told me that within two years, most vehicles end up being converted to the old manual adjustment system.

So the question arises

First, many truck drivers blindly trust automatic adjusting arms, seeing them as miracle tools. After all, the mandatory standard for automatic adjusting arms hasn’t been in place 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, so once we truck drivers accept them, we rarely check or pay attention to them, not knowing when they might completely fail or even imagining that they could fail entirely in just over a year. When driving on slippery roads, uneven braking can easily cause skidding accidents (even a good ABS won’t help much, as ABS isn’t foolproof in certain conditions). Worse, in emergencies, due to the loss of braking power, the vehicle might not stop at all, 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 suspicions of a quality issue. From the technical characteristics of the automatic adjuster arm, it works by using a preset brake clearance value. When the brake pads exceed the limit during use, the automatic adjuster arm drives the internal one-way clutch mechanism to reduce the clearance by one level when the brake action is completed and the arm returns, keeping the brake clearance within the normal range. After each automatic adjustment, it needs a lock like a manual adjuster arm, but we've found that failed adjuster arms cannot lock the adjusted clearance. Even after manual adjustment, the first few brakes will return to the previous state. I am not a professional, so I cannot provide specific technical data, only speculate based on personal experience. One of my previous 6×4 tractors had the same issue, and within two years, all automatic adjuster arms were replaced with ordinary manual ones because the automatic arms seemed to have a short lifespan and unpredictable issues, and they were much more expensive than the manual arms – manual ones cost a few dozen yuan each, while automatic ones were over 300 yuan. The damaged automatic arms we've found are mostly over a year old. I believe the design and technical characteristics are fine, but the key issue is the material used. Good materials would ensure a longer service life, not a series of failures within a little over a year (especially many found within two years). Of course, such products would have undergone extensive testing before R&D and market release, with specific requirements for usage frequency and life. Since every brake press almost simultaneously engages the internal parts of the adjuster, this relates to how many times the parts are allowed to be used (for example, tens of thousands of brake presses), placing strict material requirements on all components of the adjuster arm.

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 often, so naturally, the wear is much lower and the lifespan seems longer. Vehicles running on complex roads or hilly areas, where braking is more frequent, 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 often used in mountainous areas or on rough roads brake frequently, so problems may arise within 18 months. Vehicles used 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 pass ISO/TS16949:2002 verification. But our country is vast with vastly different terrains, so some standards differ greatly from reality. Based on current issues, it seems this automatic adjustment arm falls into the 'wearable parts' category for vehicle maintenance. But it is, after all, a critical component related to life safety, and manufacturers absolutely must not edge quality against regulations for profit!

Sincere suggestion

Finally, I suggest manufacturers remember, brakes are no minor matter—they impact countless lives and families' happiness and should never be handled carelessly! The lifespan should definitely not be designed around the warranty period, nor should product quality be judged by standards that lack real-world basis. Product usage period should be clearly indicated during promotion, with reasonable scientific explanation of performance so end users understand how to maintain and service the vehicle correctly, ensuring its components are always in normal condition.

I also strongly suggest truck OEMs strictly check product quality when selecting parts, and not let a brand's component issue damage your reputation.

At the same time, I strongly recommend that drivers pay close attention and check regularly, because you never know when your brakes may lose a few hubs' worth of stopping power. There are serious safety risks, and safety is the quickest route home.