Brazilian GP: Belts and tyre woes ruined Valtteri Bottas's F1 race

Bottas qualified fourth and looked a contender to finish on the podium when his Williams team-mate Felipe Massa earned a five-second penalty for speeding in the pits at his first stop.

But the Finn lost time at his second pitstop to have his crotch seatbelts re-tightened and couldn't recover, eventually finishing a lapped 10th.

The Finn said he suffered severe graining of his left-rear tyre during his third stint, which ruined his race.

"There was a big band of massive graining, so I think it was a construction problem or something in the left-rear," Bottas said.

"That slowed me down quite a bit, I was sliding a lot and the tyres were destroyed really quickly.

"Then the last stint was compromised because it became really long, so I just needed to try and get to the end without stopping again."

Bottas had hoped to continue with loose belts, but Williams performance chief Rob Smedley said they had to be re-tightened for safety reasons.

"I instructed the mechanics to check everything because you're dealing with safety," Smedley explained.

"So we put ourselves out of contention for any big points because we added something like 12 seconds to the stop, but there was no question we wouldn't do that."

TYRE PROBLEM A MYSTERY

Smedley said Williams was puzzled as to why Bottas suffered worse rear tyre graining than team-mate Massa, who recovered from a five-second penalty and a delay from mistakenly stopping at the McLaren garage to finish third.

"We're trying to understand what happened with the rear tyres; both drivers complained to a certain extent in the second stint that it was difficult," Smedley said.

"We subsequently found that Felipe had a plastic bag stuck in his front wing, which was losing him performance.

"For Valtteri the graining came a lot earlier than we expected.

"The third stint for him we have to investigate properly as to why the rear tyres were in such bad shape compared to Felipe.

"Valtteri was also unfortunate to pick up a visor tear-off that got stuck in the endplate of the rear wing, so there are a lot of mitigating circumstances."