07
2026
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05
Is it really good to release the front-wheel brake? Why does no one talk about not being able to stop?
With the continuous advancement of automotive research and manufacturing technology, as well as the gradual improvement of industry regulations, the braking safety of domestic commercial vehicle models is steadily improving. However, it is undeniable that there is still room for further improvement in domestic trailer registration and inspection, as well as truck drivers' understanding of braking systems.
This situation is particularly evident when it comes to registering trailers with ABS, matching the tractor and trailer, and releasing the front wheel brakes. To help truck drivers have a clearer understanding of heavy-duty truck braking safety, we brought in a real truck and, under a fully loaded condition of 47 tons, observed how its braking performance would be.
▎ EBS Model Line Change Braking: Tractor and Trailer Mismatch?
In daily operations or planning, many truck drivers in the community have either experienced or seen friends buy a tractor equipped with EBS or ABS. However, when choosing a trailer, in order to save money or reduce vehicle purchase costs, they may opt for a trailer without EBS or ABS. This situation is also referred to as a tractor-trailer mismatch.
So, what dangers might arise during an actual emergency braking with such a match? Will the vehicle be able to stop smoothly? We conducted full-load tests to find out.
First, we unplugged the EBS lines of the Mercedes-Benz Actros C model with the main trailer equipped with EBS, which caused the trailer adapted to the vehicle to lose the functions of EBS and ABS. Afterwards, we conducted a full-load braking test from 60 to 0 km/h.
After actual testing, in this state, the vehicle's full-load braking distance from 60-0 km/h is 26.84 meters, which is a full 2.2 meters longer than the average braking distance we previously measured for vehicles with fully functional EBS (24.64 meters).
The gap is still quite obvious. In actual driving, it may be precisely this 2.2 meters distance that can prevent many major traffic accidents. Of course, in this test, if you think that the only disadvantage is the increased braking distance, then you would be gravely mistaken.
Since the trailer no longer has the functions of EBS and ABS, the trailer experienced wheel lock-up during the actual braking process. Coupled with the fact that the tractor's EBS was functioning, the braking force was applied earlier, which also caused the whole vehicle to fishtail and understeer. If this were in an accident, we can imagine just how severe the consequences could be.
In addition, in this section, regarding the high safety redundancy feature of the EBS function, we disconnected the control air pipe of the trailer and only connected the cable to retain the electrical signal, and conducted another full-load brake test on it.
The test results showed that the vehicle could perform normal braking, the vehicle's braking response was timely, and it also had the effect of preventing the trailer tires from locking up.
I believe that from these two tests, truck owners can clearly see the dangers caused by mismatched tractor-trailer combinations. Therefore, after purchasing a high-spec vehicle with the EBS function, it is also necessary to match the vehicle with a high-spec trailer to ensure consistency in the tractor-trailer combination. At the same time, professionals should properly calibrate the tractor-trailer match to maximize our driving safety.
▎What are the pros and cons of extending the distance by 20% and releasing the front wheel brakes?
Subsequently, we conducted full-load braking distance tests after releasing the front-wheel brakes for the currently abundant ABS vehicles on the market, specifically vehicles where the tractor has ABS functionality but the trailer does not.
After actual testing, in this condition the vehicle's full-load braking distance from 60-0 km/h is 30.73 meters, which is a full 5.25 meters longer than the average braking distance we previously measured with the fully functional EBS (25.48 meters). The braking distance has been extended by about 20%, and the trailer tires locked up, also causing a risk of jackknifing.
I believe car enthusiasts can also see that in this test, the braking distance is not just a little longer—it clearly exceeds the length of a large sedan. So what if it were at an even higher speed? The potential danger of an accident is imaginable.
So why do some truck drivers still do this?
In fact, the practice of releasing the front wheel brakes has a long history in China. The reason is that after doing so, when the vehicle is in an emergency braking situation and the tires lock up, the vehicle can still make an emergency turn, which helps the vehicle to avoid danger. Another important reason is to prevent the phenomenon of 'nose diving' caused by inconsistent responses of the primary towed brakes during emergency braking.
But this practice emerged at a time when vehicles had not yet fully adapted to the ABS function. At that time, once a vehicle performed an emergency brake, the wheels would inevitably lock. However, nowadays, ABS has become a standard feature in vehicles, and the wheels no longer lock, and the country is actively promoting the widespread application of more advanced braking assistance systems such as EBS and AEBS.
It can be said that some 'old methods' are time for truck drivers to abandon. It may not be that they are bad, it's just that they no longer suit the current era.
▎Conclusion
Through testing, we can see the adverse effects on vehicle braking distance when the tractor-trailer matching is inconsistent and when the front-wheel brakes are released. These effects will ultimately impact other road users as well as the truck drivers themselves.
Think about it carefully, when you are willing to spend a large amount of money to buy a tractor, why be stingy when it comes to trailer and brake matching that concerns life safety? Isn't that like losing a watermelon to gain a sesame seed? Every brake by truck drivers is not only a test of safety but also a test of life itself. We hope every truck driver can depart happily and return home safely.
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