The Walkinshaw Andretti United driver was fighting Andre Heimgartner for victory in a soggy 200-kilometre race on Saturday, only for his hopes to be dashed shortly after his second compulsory stop.

That was due to his right-rear wheel parting company with the car which meant a slow trip back to the lane and an unnecessary additional stop that sent him tom the back of the field.

While wheel nut failures have occurred in the Gen3 era, as recently as the Bathurst 500 earlier this year when Cam Waters lost a wheel, in this case it was a fitment issue rather than a component issue.

“No, no component failure, [the] spindle’s fine,” WAU team principal Carl Faux told Speedcafe.

“Obviously, there’s been a few issues with that in the category, but none of that. The wheel clip’s still intact; just the wheel wasn’t seated and the nut wasn’t done up correctly.”

Faux agreed that Mostert was a big chance to win the race had he not lost the wheel.

“It was disappointing,” he said. “It was looking pretty good until then, wasn’t it?

“We had fast cars, it was good in the wet. Not quite as fast as we wanted to be in the real wet but it dried out quite nicely while still being wet.

“Chaz was sort of biding his time for that last stint, really. We never got to show what we could do.”