The delayed pitstop that cost the #8 Toyota of Sebastien Buemi, Brendon Hartley and Kazuki Nakajima victory in the Six Hours of Bahrain was caused by a wheel nut failure, according to Toyota technical director Pascal Vasselon.
The #8 Toyota was already on the back foot compared to the #7 sister car when a long stop for the #8 car diminished any remaining hopes of victory.
Toyota mechanics struggled to fit the left front wheel to the car before having to fit another wheel altogether, delaying it significantly and dropping it briefly behind the #36 Alpine A480-Gibson and down into third place overall.
Hartley was eventually able to re-pass the Alpine and regain second, but the sister car driven by Mike Conway, Jose Maria Lopez and Kamui Kobayashi went on to win by nearly a minute, further solidifying their championship lead in the process.
After the race, Vasselon confirmed that a wheel nut issue was the root cause for the slower stop when Brendon Hartley brought the car in.
“The thread did not engage properly,” Vasselon said. “When this happens, we have to change the nut. As part of our procedures, we always have a spare set ready. We just changed the wheel, and then we repaired the nut.”
The Toyota boss further explained that the entire wheel had to be replace because the wheelnut is an integral part of the wheel design and can not be replaced separately.
“The nut is together with the wheel. We have a captive wheel nut,” Vasselon said when asked why the entire wheel was replaced as opposed to just the wheel nut.
“The wheel comes with the wheel nut. So if you damage the nut, you have to change [the entire wheel].
Tyre degradation was ‘on the knife edge’
As anticipated, the two Toyotas struggled greatly with tyre degradation in the desert heat. Teams up and down the paddock strugged with degradation of rubber and Toyota similarly felt the heat as temperatures reached as high as 34 degrees celsius during the race.
According to Vasselon, the higher rate of degradation for the #8 car was also an important factor in the race outcome.
“The average race pace was dominated by tire deg,” Vasselon said. “It was somehow on the knife edge. Between our two cars, clearly the difference has been made on tire degradation at some point.”
“Two times in the race car 8 had very big degradation and lost contact with car 7. Compared to Alpine, it started very, very close and then it’s not totally clear why we could manage the tires better than them because fundamentally, they should have been in better shape.”
“We had a different tire strategy, which probably helped us to survive better.”
