The next-generation NASCAR Cup car – to be introduced for the 2021 season – will use wheels with single securing nuts, replacing the five-nut rims that have been part of the sport for many decades.

According to NASCAR officials the move to a single-nut rim has been made necessary by a planned change to 18-inch aluminium wheels from the current 15-inch steel items.

The single-nut wheels, which have been commissioned from German manufacturer BBS, were revealed in the latest test of the Next-Gen car at Auto Club Speedway, Fontana on 2nd-3rd March. NASCAR senior VP of innovation and racing development John Probst said that with the wheel rim size moving to 18in to more closely relate to current production cars, it was necessary to ensure the wheels were suited to a racing environment.

“Once you get to an 18-inch aluminium wheel, the next step for us is to make sure that… under racing conditions it will accept the durability that we need to finish races and then also finish multiple races – to do that, the single nut was our only option,” Probst said.

The plans have already caused controversy among many fans of America’s top motorsport category, but Probst argues that the major visual difference will only be in the appearance of the wheels, with little change to pit stop procedure.

“A lot of times when we say single lug nut, people fear that it (will be) an open-wheel style pit stop where people will be on their knees waiting for the car to come in. We don’t intend to change anything with respect to how the pit-stop flow is executed.

“There will still be guys coming off the wall – there will still be a premium for that athlete to come off the wall, get to the right side of the car, make that tire change, get over to the left side of the car and make the tire change. From the look and feel of the pit stop, we don’t see any significant changes.”



He added that there would be little gain to the time taken for stops as the new nuts would require more torque to be properly secured – ensuring the nut was completely tight would be vital. “The steel wheel is more forgiving and (drivers) can handle loose wheels a little bit better – we did some durability studies and if you leave lug nuts loose on an aluminium wheel, you reduce the durability of the wheel by around 30 per cent.”

Probst pointed out that switching to the single nut would improve efficiencies as the same nut would likely be retained for the entire race, whereas currently nuts are glued over the holes of wheels before they are fitted to the car in a pit stop – nuts removed are simply swept up after a stop.

“There are times when we have to open up the garage or pit road early on race day for no other reason than for the race teams to glue up 11 sets of tires – (with the new nut) they can just use the wheels as they are without being glued,” he said.

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Prior to the fourth on-track test of what is being described as the ‘P3’ (third prototype) of the Next-Gen car, Probst indicated that the specification of the car was very close to being finalised.

“We feel like this car is probably 99 per cent what we’re going to compete with next year, and then some of the vendors that we’ve selected have been able to make parts available that will be identical to what we’re racing next year,” he said.

Andrew Charman is a regular contributor to PMW. He has been working in motorsport for more than 35 years, specialising in Touring Cars and US motorsport, particularly NASCAR.

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