Toro Rosso duo Carlos Sainz and Daniil Kvyat admit that their team is heading into the Abu Dhabi Grand Prix still unsure about whether or not it has cured its rim problems.
Both drivers were confined to the garages for second practice at the Yas Marina circuit after Kvyat suffered two rim failures in Friday's running.
Tweaks to the car, and especially the rear suspension, allowed both men to get running again on Saturday, but they endured a frustrating time in qualifying.
Ahead of the race, Sainz in particular revealed that Toro Rosso could not be totally sure that the situation was fully resolved – because it did not have a definitive answer about what was causing the problems.
"The team has put all of its available resources on fixes to the car to make sure we don't have any contact with the tyre and the rim to the car or the floor," he said.
"We've done everything we can, but I think the problem still is that we don't know the cause of the punctures.
"Without knowing the cause, you're always going to try to tune the whole car up to make sure it doesn't happen, but you're not going to be 100 percent sure it won't happen again."
When asked if, however, the FIA was satisfied the cars were safe to race, Sainz said: "It's happy because it sees the tyres are not exploding and also we can see less indications of problems in the tyres, of contacts.
"So we are all happy and confident but we are not yet 100 percent to say nothing's going to happen [in the race]."
Kvyat said that the team had to make performance compromises because of the problem, but the situation was not as worrying because Abu Dhabi was the final grand prix of the season.
"I can say that compromises have been made because the FIA hasn't been pleased with things going on," said the Russian. "I think we've managed to comply with their requests and we believe the race should be OK.
"But it's all a bit odd and I think the team will look into it. It is the last race with the current car so it would've been a bit worrying with two or three races to go but for now I think we should just survive."