Behind the broken brake pedal of a "million-dollar luxury car": the underestimated leg strength of ordinary people.

Author | Zhou Zhiyu

On October 8th, a braking test video released by Dongchedi made the V800 a focus of attention in the automotive industry. The testers stated that during emergency braking from 100 km/h to 0, the pedal brackets of all three vehicles broke.

After the video was released, some netizens questioned whether the test was conducted under extreme conditions and whether the driver pressed too hard. Besides the reason why the support broke, the question of how much force an ordinary person can exert when pressing down has also become a point of contention in this incident.

That evening, Zunjie responded, stating that the braking system was developed and verified to meet or exceed relevant national and industry standards, and that no brake pedal bracket base breakage failures had occurred in actual user scenarios. The company also announced an optimization of the component's design, offering a free upgrade option to existing customers.

Dongchedi denied the existence of any "violent testing." A source close to Dongchedi stated on the evening of October 8th that emergency braking from 100 km/h is a basic test in real-world car testing, and similar scenarios may occur during high-speed driving. The test used normal, forceful braking.

As of the morning of October 9th, the specific results of the on-site investigation had not yet been released. However, JAC Motors, after hitting its daily limit down on October 8th, experienced another limit down. Previously, its stock price had surged by over 40% in the second half of September due to factors such as the release of several new models, including the Zunjie.

In connection with this test, the 1600N pedaling force was repeatedly compared with the data in the national standard: whether the former exceeded the foot strength of ordinary people, and whether the latter could be used to judge whether the test was "too forceful".

In dangerous situations, ordinary people may press the pedal with far more force than they would in normal driving. The safety margin of the pedal should also take into account the possibility of a person pressing it too hard in a panic.

Slam on the brakes

According to a video from Dongchedi, the third test vehicle recorded a maximum pedal force of 1596 N and a braking distance of 38.44 meters during its first braking maneuver. During the second braking maneuver, the support bracket broke, and the maximum pedal force recorded this time was 1612 N. The driver stated that he could only gradually decelerate using the Park (P) gear, ultimately stopping the vehicle 140 meters away. The previous two test vehicles experienced support bracket breakage during their third and fourth emergency braking maneuvers, respectively.

The appearance of the number 4589N in the video has shifted the discussion to "violent testing." Some have questioned whether the testers applied forces that would be difficult for an ordinary driver to achieve.

Dongchedi denied this. A source close to Dongchedi stated on the evening of October 8th that emergency braking from 100 km/h is a basic test in real-world car testing, and similar scenarios may occur during high-speed driving. The test used normal, forceful braking. Regarding the 4589N screenshot, Dongchedi explained that the camera and the testing equipment screen refreshed out of sync, creating a digital ghosting effect; the actual recorded peak value was 1612N.

In its statement that evening, Zunjie described the relevant tests as "non-standard extreme test conditions" and stated that since the first batch of vehicles were delivered, no brake pedal bracket base breakage failures have occurred in actual user scenarios. The company stated that it will review the design verification, test boundaries, and production quality management of the relevant components.

Besides the disagreement between the two sides regarding the emergency braking situation, the plastic bracket in the disassembly footage has also raised questions: Why not use metal for the components that bear the braking force?

In automotive engineering, one development goal for reinforced plastic pedals is weight reduction. Loïc Lefebvre, a research and development expert at automotive parts supplier Carbody, emphasized in his presentation that material strength is key to achieving pedal weight reduction, while design support is used to optimize the structure and performance of safety components. His published solution uses a composite material skeleton combined with glass fiber reinforced polyamide, with the material and skeleton sharing the load.

The development documents for the 918 Spyder pedals, released by Porsche and ZF engineers, reveal another side of this trade-off. The project used fiber-reinforced plastics to reduce weight, while the original design requirements for the steel version were retained. The verification also included material-related factors such as temperature and moisture content.

Tests revealed that high temperatures and moisture content reduced the maximum load-bearing capacity. The development team therefore adjusted the design, sacrificing some weight, to ultimately meet the product's strength requirements. The extent of weight reduction was also constrained by the predetermined strength requirements.

Reinforcing materials can bring weight reduction benefits, but they must be developed in conjunction with the structural design and validated under appropriate environmental conditions. The rationale for material selection and the final ability of the component to withstand heavy foot traffic are linked during the development process.

According to Wall Street News, the incident has already affected some orders. A representative from JAC Motors' investor relations department responded to the Dongchedi video, saying, "We have recorded the situation and reported it to the relevant departments. Please pay close attention to further developments."

The Zunjie customer service consultant also responded that the brand has taken note of the test video and the relevant matter is in the process of verification and processing. Further progress will be announced through official channels. All vehicles under the brand undergo rigorous testing of the brake pedal before leaving the factory and meet the relevant factory standards.

Residual amount of pressure

1612N, which is approximately 164 kilograms of force, is roughly equivalent to the force exerted on a 164-kilogram object. Putting this value directly in the driver's weight makes it easy to think that only very large people could achieve this.

The pedaling motion in a car also involves the active forward pushing force of the legs. The driver sits in the seat, their body supported, and their leg muscles apply force to the pedals. In this posture, the force exerted by the feet can exceed the force corresponding to their own weight. There is an active force process between body weight and the pedal reading.

Volvo conducted a driver study in 1998. Thirty-five drivers who drove more than three days a week were placed in a simulator with a fixed base. The study set up controlled braking and simulated emergency braking scenarios, recording how they pressed the pedals.

In the valid force measurement data, the average pedal force of the controlled braking was 281N, which rose to 796N during simulated emergency braking, about 2.8 times the former, with the highest reading reaching 1793N.

Caption: Pedal force data from Volvo's 1998 simulated driving study.

More notably, in the emergency scenario, the group that felt they hadn't braked hard enough still applied an average force of 591N; whereas in this simulation device, 160N was sufficient to achieve maximum braking effect. There is a significant gap between a person's subjective feeling and the force required by the braking system: even when the system has braked sufficiently, a person may still feel they haven't braked enough.

A 2010 study published by the National Highway Traffic Safety Administration (NHTSA) also included another measurement. The study recruited 64 participants from two age groups: 18-25 and 65+. After the vehicle was put in Park, participants were asked to fully depress the pedal three times, and the study recorded the maximum force applied.

The highest reading in the Mercedes R350 group was approximately 1766 N, and in the Volvo S80 group it was approximately 2117 N. Volvo's 1998 test observed reactions in sudden scenarios, while the NHTSA test required participants to actively exert all their strength. Both methods recorded applied forces exceeding 1600 N.

There is already measured data on how much force an average driver should apply under specific circumstances. However, the amount of operational force required for full braking is another issue addressed in the standards.

The 2017 version of GB 7258 requires that the pedal force for passenger cars to achieve maximum braking efficiency should be less than or equal to 500 N. It focuses on the amount of force required for the driver to fully engage the braking system; the vehicle should achieve maximum braking efficiency within this range of operating force.

Even with the braking system fully engaged, the driver may still apply additional force to stop the vehicle. This extra force must still be transmitted through the pedal and its supporting structure. Therefore, the pedal design must not only meet the required operating force but also consider the load-bearing capacity when the driver continues to apply force.

In this discussion, two opposing comparisons emerged regarding structural strength: some compared 4589N with 1500N, arguing that the test far exceeded the standard; others compared 1612N with 2000N, believing that the pedal did not meet the standard.

1500N is derived from the recommended industry standard QC/T 788—2018 and is the loading value for the longitudinal strength test. This standard mainly applies to mechanically articulated metal pedals; other types can refer to it for implementation. The test involves first fixing the device in the actual vehicle configuration, then applying a longitudinal force of 1500±20N perpendicular to the pedal surface and through its geometric center. This force is held for 5 seconds and then unloaded, and the test is repeated 5 times.

Caption: QC/T 788—2018 Strength Test Clauses

Next, the loaded parts are inspected: permanent deformation should not exceed 5 mm, and there should be no cracks or damage. The standard requires the parts to withstand this load; 1500N is the verification condition, and a qualified pedal should remain structurally intact after the test.

The origin of the 2000N figure is linked to an industry discussion on increasing the verification load. In August 2025, the China Association of Automobile Manufacturers (CAAM) publicly solicited opinions on the draft group standard for electronic brake pedals, proposing a longitudinal load of 2000±20N or agreed upon by both the supplier and the buyer, held for 5 seconds and repeated 5 times.

The drafting instructions explained the reasons for the adjustments: companies felt that 1500N was too low and suggested increasing it to 2000N. At the same time, since plastic and resin materials are affected by temperature, the test temperature should also be clearly specified. Therefore, the draft includes room temperature or a temperature condition agreed upon by both the supplier and the buyer. This group standard for electronic brake pedals was officially released at the end of 2025.

An engineer from a traditional automaker stated that traditional automakers have a series of requirements for pedal force, taking into account pedal deviation, lateral force application, and rapid heavy pressing. The core requirement is sufficient safety redundancy even under extreme conditions.

Another car company engineer bluntly stated that in an emergency braking situation, all the driver needs to do is one thing: slam on the gas pedal.

General Motors' 2007 pedal module specification requires that extreme usage loads be considered based on the vehicle installation state, and that forces can be applied to any point on the pedal surface; the load in the braking pedal direction is 2700N, and the lateral load is 440N, and it is required that no permanent failure or unsafe working conditions occur under the corresponding extreme conditions.

The aforementioned 918 Spyder pedal design requires that it not break or crack under loads below 3000N, and must complete at least 3000 loading cycles using a 2300N, 0.7-second hard braking test. Both individual components and complete modules must undergo static and dynamic verification, taking into account the effects of temperature and humidity.

From any point on the pedal surface to lateral force and repeated hard slamming, the development requirements have broken down an emergency brake application into different force application methods. The driver's actions in a dangerous situation, when translated into the components, become these loads and operating conditions that they need to withstand.

Tracing the fracture

Clause 7.4.2.2 of the current GB 21670—2025 includes checking the manufacturer's design documents and conducting a visual inspection of the braking system as part of the strength test to confirm that the pedal and its bracket and other components have sufficient strength.

The force measuring device under the foot records the force applied to the pedal. This force acts on the pedal mechanism, and the distance from the point of application to the pivot, the shape of the bracket, and the connection method all affect the force on various parts of the component. In failure investigations, the force records, the location of damage, and the condition of the components each play their respective roles.

A Ford recall illustrates how this process unfolds. In August 2019, three reports of Mustang brake pedal bracket fractures entered the internal review process. Ford analyzed the returned parts and confirmed that the failure mode was brittle overload. A subsequent search of similar reports revealed that the bracket fractured at the pedal pivot point during sudden emergency braking.

The investigation continued to the material change. Ford explained in its recall report that the bracket in the affected automatic transmission models had been changed from nylon to polypropylene, which reduced the robustness of this specific design against impact braking loads; the engineering specifications and design verification procedures also did not allow sufficient margin for related changes.

The recall notice in China also linked material changes, design margins, and emergency braking fractures. For these vehicles, the load-bearing performance of the bracket after the material adjustment became the key to the investigation. In 2020, Ford recalled 38,005 2020 Mustang automatic transmission vehicles in the United States, and in the same year, it recalled 2,627 imported 2020 Mustang vehicles in China, replacing the brake pedal bracket assembly free of charge.

Another recall of the Audi Q3 began with welding issues in the supply chain. On August 24, 2020, a supplier reported a potential welding problem to Audi, and an investigation was immediately launched, screening and isolating problematic parts. On September 5, bench testing was initiated to assess the failure mechanism, likelihood of occurrence, and consequences.

The investigation revealed that the welding connection between some pedal arms and the panel may have been incorrect. Under the impact load of emergency braking, the panel could deform or detach. Even if the panel detaches, the pedals would still be operable, but the foot contact area would be reduced; this consequence was also included in the safety assessment. On December 9, Audi decided to recall potentially affected vehicles.

This recall in the United States involves 313 vehicles. The solution is to inspect the welds and replace the entire pedal set if necessary. The supply chain has also implemented full pre-shipment inspections and improved monitoring of the welding process. The investigation ultimately traced the specific connection procedures and inspection measures.

The phenomenon of fracture or damage is gradually traced back to specific aspects of materials, design verification, or manufacturing connections through component analysis and testing.

Zunjie has announced optimizations to the design of relevant components, offering free upgrade options to users who have already delivered their products, and reviewing design verification, test boundaries, and production quality management.

During emergency braking, the braking system may have already worked fully, but the driver may still feel they haven't applied enough pressure and continue to apply more. Studies have documented this type of force application, and car manufacturers should provide sufficient margin for it. When an ordinary person slams on the brakes in a dangerous situation, the car must be able to stop, and the pedal must also be able to withstand the pressure.

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