Recently, several photos were exposed of the Xiaomi SU7 running off the track and crashing into a wall due to failure of the braking system.
One of the accidents occurred at the Shanghai Tianmashan Circuit. It was reported that the vehicle was driven by the well-known racing blogger @堂主撩车. From the photos taken at the scene, the Xiaomi SU7 he was driving did not suffer any serious damage. The A-pillar was intact, and even the hood was not lifted, but it was said that the airbag exploded.
A chat record online shows that the blogger said: "There are no brakes at all. I stepped on the brakes, but there was no response. And when it wasn't braking, the brake pedal felt very good, but it just couldn't stop, there was no brake at all."
Generally speaking, in a mechanical braking system, the force of the brake pedal is positively correlated with the braking force, and the driver can also sense whether the braking system is normal from the pedal feedback.
However, as technology develops, a brake-by-wire system was born, which does not require mechanical coupling between the brake pedal and the brake disc. In other words, the brake feel comes from signal control rather than mechanical feedback.
Xiaomi SU7 uses Bosch DPB2.0 intelligent decoupled brake system (Decoupled Power Brake) + ESP10.0, which is a fully decoupled wire-control brake solution. The brake pedal and the brake system are not the traditional mechanical solution of brake pedal-vacuum booster-brake master cylinder-oil pressure to push the brake. The brake pedal is only responsible for inputting pressure signals, and the electronic control system applies pressure to the brake.
If a node in the above link fails, it is possible that what the blogger said in the chat: "The brake system has thermally degraded or even failed, but the foot feel is still normal."
Another possibility is that the Xiaomi SU7 is originally equipped with Michelin PILOT SPORT EV tires, which are road tires. They are designed to meet the needs of daily road conditions and may also suffer from heat exhaustion when dealing with track conditions. When the tires are running at high speeds and under heavy loads, friction with the ground will generate a lot of heat, resulting in a decrease in the performance of the tire material itself, which in turn affects the grip and handling performance.
The curb weight of Xiaomi SU7 Max is as high as 2.2 tons, which puts a lot of pressure on the tires and braking system.
At present, no authoritative organization has given a clear conclusion on this accident, and the above analysis is all speculation based on technology and logic.
Xiaomi SU7 has highlighted its competitive feel and high performance during its promotion, so it is understandable that it is used for testing by racing enthusiasts.
It is worth noting that although the racing blogger ran off the track, the track is the best place to test vehicle performance, and there are redundant buffer areas and safety guardrails on the edge of the track. Compared with the "novice" who treats the road as a track, this track crash can only be said to have touched the performance limit of Xiaomi SU7. There is nothing wrong with driving within the ability and in a safe place.
