In a small overlap crash, what exactly is the "wheel detachment to protect the cabin" safety strategy? Can you introduce it again?
First of all, we want to emphasize that "wheel detachment to protect the cabin" is the force transmission strategy adopted by Xiaomi EV when dealing with small overlap crashes. It does not mean that "wheel detachment" will simply occur in any crash situation, nor is it "as long as the impact is severe, all cars will lose their wheels".
The "wheel detachment to protect the cabin" strategy is fully described as "body sliding + wheel rotation", not a simple "detach wheels upon impact" behavior. A small overlap crash is an extremely severe crash condition. Because only a small area of the front of the car contacts the obstacle, when a crash occurs, it will bypass the front longitudinal beam, which is the core energy-absorbing path. This may cause the passenger cabin to be directly impacted by the collision force of the object, causing serious injury to the occupants. The "force dissipation" strategy is to guide the body to slide and make the wheels move in a controlled manner through the design of the body and chassis structure, thereby preventing body components from intruding into the passenger cabin, achieving the effect of "first transmit, then dissipate force", and minimizing the probability of occupant injury.
In addition, as the first line of defense, the front anti-collision beam can transmit the impact force to the longitudinal beam and its rear cross beam, achieving further dispersion of the collision force.
The purpose of the "wheel rotation" mechanism is to prevent components such as the wheel hub, bearing, and caliper from directly impacting the front bulkhead of the passenger cabin during a small overlap crash and causing intrusion, which would cause serious injury to the occupants' legs. The mechanism principle is not simply to let the wheel linkage naturally break under impact, nor is it a simple "break upon impact". If precise and robust design is lacking, the connection failure between the wheel hub and the body will be uncontrollable, and the direction of wheel movement cannot be effectively guided, meaning the "wheel detachment" effect cannot be achieved.
To implement this strategy, "wheel detachment" does not occur under any impact condition. It will only break at pre-designed fracture points that have undergone sufficient robustness design under conditions of extremely high collision energy, such as the connection between the lower control arm of the front suspension and the steering knuckle. This causes the wheel to be guided to rotate backward, and through the chamfers in front of the A-pillar and the sill beam, the wheel is effectively thrown out of the body. This is a safety strategy that requires a large amount of design optimization and verification to achieve.
During the development process, we went through extensive design and verification, and combined various structural designs at the same time, fully taking into account both crash safety and daily driving reliability, ensuring "force dissipation and wheel detachment when critical, safe and reliable in daily driving". To ensure that the wheel linkage remains reliable and durable during daily driving, comprehensive durability and abuse strength tests under extreme scenarios were conducted during the vehicle development stage, such as braking over bumps, forward rushing over bumps, and reversing over bumps. The severity of these tests far exceeds the daily driving environment, so you can rest assured.
Finally, it needs to be declared that "wheel detachment to protect the cabin" is not a patent of Xiaomi EV, nor is it the first brand to adopt this safety strategy. Xiaomi EV has also fully shared the development of safety structures and crash strategies in recent live broadcasts, and we will continue to share the principles of key technologies with you in the future.