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2026

What exactly causes a vehicle to roll over due to a mismatch in the main suspension?

Recently, while chatting in a trucker group, I saw some truckers sharing a few videos. The general content was about imported tractor trucks overturning when taking turns. Many truckers analyzed that it was due to driver fatigue, some truckers said it was caused by problems in the vehicle's braking system, and others said it was because the trailer's cargo was not loaded correctly, causing instability in the center of gravity. So, what exactly is the problem?

▎What were the configuration and condition of the vehicle involved in the accident?

From the video, we can see that most of the vehicles involved in the accidents are imported cars, and they all belong to sizable logistics companies, with some even being among the top express delivery companies in the country. These logistics companies' vehicles undergo regular inspections, and there are also certain regulations regarding speed during travel.

Theoretically, there should be no issues with the braking systems of these vehicles themselves. They are also equipped with corresponding fatigue driving systems, and some accidents occurred during the daytime, so theoretically there should be no so-called fatigue driving. However, these vehicles share several common characteristics. First, the main vehicles are all mid-to-high-end models with relatively high chassis configurations. Second, most of the accidents occurred while turning, and the relative speed during the turns was relatively high.

As for the chassis configuration of the main vehicle, most braking systems are EBS ESC (Electronic Braking System and Electronic Stability Control), and almost all are AMT. Moreover, if the main vehicle is imported, it basically uses disc brakes. As for the trailer, most configurations are ABS, and some don't even have ABS connected, and some trailers still have drum brakes.

▎The main vehicle and trailer are mismatched, causing oversteering and rollover when cornering.

From the configuration of the tractor and the trailer, we can already see some causes of the accident. The biggest problem is that the tractor and trailer do not match. If the speed is relatively high when turning, the EBS system of the tractor will start to work, beginning to brake the inner wheels of the tractor to prevent rollover due to excessive speed.

However, at this time, old trailers without an EBS system cannot perform single-side braking when the tractor carries out anti-roll braking, which causes the trailer to push the tractor. Simply put, when turning, the EBS will brake one side of the wheels (the EBS system automatically intervenes in braking, without the driver needing to press the brake pedal), but the trailer does not brake, which leads to pushing the tractor and subsequently a rollover.

Some truckers say, 'What if my tractor has EBS but my trailer has ABS, and I feel like the vehicle might slide while turning, if I press the brakes, can I save the vehicle?' Actually, if you try to brake when you feel the vehicle is about to slide in a curve, it is already too late.

First, the EBS system would definitely have detected the risk of vehicle rollover before the driver and intervened early. Secondly, EBS executes braking slightly faster than ABS. When the driver steps on the brake pedal, the main vehicle's EBS responds faster than the trailer, which could instantly cause a jackknifing, leading to an accident.

If the main vehicle has EBS and the trailer has ABS, the safer way to take a turn is to control the turning speed.

▎Mismatch between the main vehicle and trailer is common; most express and fast delivery vehicles have safety risks.

When we visited the market, we found that the vast majority of express and freight companies' vehicles have issues with tractor-trailer matching, especially logistics companies that use drop-and-hook operations. Because drop-and-hook requires frequently changing trailers, the technical condition of each vehicle varies, and although most trailers have ABS systems, the tractors are basically all EBS systems (the company uses imported vehicles with standard EBS).

Moreover, drop-and-hook transportation has relatively high requirements for timeliness, which leads to relatively fast speeds on the road, including on highway ramps, inevitably creating safety risks. Often, logistics companies using high-end models face more of such safety hazards.

● Editor's Note

Currently, the technology and configuration of tractors in China are developing very rapidly, especially in terms of chassis configuration, which has long moved from the ABS era into the EBS electronic control era. However, domestic users' understanding of tractor-trailer matching, as well as the popularity of trailer EBS, is limited, resulting in a mismatch between the technology status of tractors and trailers, creating safety risks for most vehicles on the market.

Additionally, some users, when replacing their vehicles, choose tractors with higher configurations but continue to use old trailers, which may not even have basic ABS. Some users think ABS is not effective enough when braking, so they simply do not use it, which is completely wrong. If your tractor is equipped with EBS, then for your safety, you must also equip your trailer with an EBS system. This ensures proper tractor-trailer matching, allowing you to drive without concerns.

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