Sebastien Buemi's spectacular accident in practice for the Chinese Grand Prix was caused by the failure of the right-front upright – which also prevented the car's wheel tethers from keeping wheels from entering a spectator area. Both wheels flew off Buemi's car under braking for Turn 14 near the end of first practice in Shanghai, pitching him into the barriers.
An investigation by the team has concluded that the incident was caused by a failure of a new upright design introduced for this weekend's race. Exactly what went wrong to cause the malfunction has not yet been established, however.
Once the right upright failed, then the load on the left-hand side one was too great for it to handle – which is why it failed at the same time. The team also concluded that the wheel tethers did not work, with the tires being pitched over the spectactor fences, because the tethers are attached to the part of the uprights that broke off.
Toro Rosso fitted uprights from a previously used proven design to both its cars for the rest of the weekend's sessions.