NASCAR NextGen Wheels: The Scientific Argument for a Single Lug

The NASCAR NextGen car will feature a wheel with a single lug nut instead of the five-lug pattern that has been a NASCAR mainstay. While some decried the switch from tradition, this change was necessitated by physics, not form.

TL;DR

  • NASCAR is moving to an 18″ wheel because manufacturers want stock cars to be more like production cars.
  • An 18″ steel wheel would be too heavy
    • Pit crews would have to manipulate 70 lbs of steel
    • A heavier wheel would make the car less agile
    • A 70 lb loose wheel struck by a racecar become a deadly projectile.
  • The 18″ wheel must be aluminum
  • Aluminum isn’t as strong as steel: it warps and deforms more easily. It’s also more expensive.
  • For the wheels to stay on the car and not be irreparably damaged, it is absolutely essential that the wheels be well-fastened to the car with even torque all around the wheel.
  • We know from experience that getting all five lugs on perfectly doesn’t always happen. This presents a safety issue, as well as a cost issue if a wheel is damaged.
  • Therefore, one lug is the only feasible solution .

15″ vs. 18″

The five-lug steel wheel used by NASCAR until 2021
The NASCAR-approved AERO 59-Series Race Wheel

NASCAR has used steel wheels for a long time. At right is the Aero 59 NASCAR-approved steel racing wheel used by many of the teams.

The wheel size is 15 x 9-1/2″ and it weighs 27 lbs. The tire (without inner liner) weights 24 lbs. Add on 5 steel lug nuts and we’ve got 50+ lbs for the tire carrier and changers to manipulate.

Why 18″?

Almost no passenger cars run 15″ wheels anymore. Even my 10-year-old Mustang has 17″ wheels. Manufacturers participate in NASCAR to sell cars. Their sport cars have 18″ wheels (or larger), so the NextGen wheels will be 18″.

Why Aluminum?

An 18″ NASCAR NextGen steel wheel would be prohibitively heavy. A 18″ x 9″ steel wheel by US Wheel is 40 lbs. (I couldn’t even find a 18″ x 9-1/2″ steel wheel online.)

Heavier wheels make handling more difficult. Their larger moment of inertia makes harder to accelerate or decelerate. A car with heavy wheels just isn’t as agile as a car with lighter wheel.

The weight is also an issue in terms of pit stops. A steel wheel plus tire would be in the neighborhood of 75 lbs. That’s harder to carry and manipulate — and more dangerous if one gets loose.

The Summit racing catalog boasts 17,305 wheels with 18″ diameters. Only 34 of those are steel. The others are called ‘aluminum’, but they’re actually aluminum alloys that contain silicon and magnesium, plus other elements that improve the material’s properties.

Steel vs. Aluminum

There are many variations in alloys for both steel and aluminum, but this broad comparison is adequate for our purposes.

  • DENSITY: Steel (which is mostly iron and carbon) is about 2.5 times denser than aluminum alloys. A piece made of aluminum that weighed 10 pounds would weigh 25 pounds if the exact same piece was made out of steel.
  • HARDNESS: Steel is harder than aluminum, making it more resistant to dents, dings and scratches. Steel is less likely to deform, warp or bend due to force, heat or a combination of the two.
  • CORROSION: Aluminum is much more corrosion resistant than steel. Steel has to be painted or otherwise treated to protect it from rust. Aluminum doesn’t need any further treatment
  • MALLEABILITY: Malleability is how easy it is to shape something. Aluminum can be shaped to form more complex and intricate parts.
  • COST: Steel is cheaper per pound than aluminum.
  • LOOKS: Because aluminum can be shaped more easily, you can make wheels that look more like what we find on passenger cars.
The current 15" wheel on the left, with the prototype new 18" NextGen wheel on the right.
Which of these two wheels looks more like a production car wheel?

Why a Single Lug?

Once the choice of aluminum alloy for the NextGen wheel was made, going to a single lug was essentially the only option to satisfy financial and safety constraints.

Teams will have to buy new wheels. They keep two sets per car so one set can be mounted while the other is being used at a track. Each car needs has upward of six to eight dozen wheels.

Given the cost of aluminum wheels, the teams don’t want to have to be replacing them frequently. Aluminum isn’t as hard and forgiving as steel, which means that one loose lug can ruin the wheel to the point where it has to be scrapped.

Getting the Wheel Tight

Manufacturers recommend that you tighten lug nuts in a star pattern.

The star-shaped pattern that tire manufacturers recommend for tightening lug nuts.

This pattern prevents warping the wheel by applying uneven torque. But it’s slower. That’s why NASCAR tire changers don’t do it that way.

Aluminum wheels won’t going to stand up to the same kind of abuse as steel wheels. You have to be positive that all five lug nuts are properly tightened, and we know from experience that this doesn’t always happen. In addition to destroying an expensive wheel, there are significant safety issues from a loose wheel, not to mention a racecar driving on three wheels. The central hub design for the NextGen wheel makes much more sense for cost effectiveness and for safety.

Will Pit Stops Change?

“In terms of timing, the torque is higher on the single lug, which means they have to leave the gun on longer. In our testing, we’ve found that it takes approximately half a second to properly tighten this new lug. Today, a good tire changer can remove five lugs in about .8 seconds. So, while pit stops may be a touch quicker next year, it won’t be a significant difference.”

John Probst, NASCAR Senior Vice President of Racing Innovation

Nate Ryan points out that the limiting factor in pit stop speed will be the jackman and the gas man and NOT the tire changers. He predicts a potential change in pit road salaries.

And, like me, he predicts that there will be a huge cry from some fans (as with EFI) and then the matter will be pretty much forgotten — as long as it makes the racing better.

10 Comments

  1. Loving your posts this season!

    Two questions:
    – I read that somehow the single lug is attached to the wheel, so not only will teams not have to glue on hundreds of lugs on race weekend, they won’t even have to glue on the one per wheel this uses. Can you explain or find image of how this works? And talk about an unpaid internship job that’s no longer needed 🙂

    – Relevancy question – as one who just rotated the tires on my daily driver, are there reasons why we should or shouldn’t use a single lug on a passenger car? Only things I could think of would be the cost to manufacture and the ability of common folks like me to take this off and on by themselves, in their garage and on the side of a road fixing a flat.

    Thoughts?

    • The single nut is not pre attached to the wheel (like how currently 5 lug nuts are glued on). The socket on the pit gun is supposed to capture the nut during removal, and reinstall the removed nut on the new wheel. As far as an internship that’s no longer needed, most tire changers prefer to glue their own nuts on so they know how tacky the glue is.

    • The other issue with single lugs on street cars is that it is impossible to detach and reattach without a pneumatic lug wrench. The torque required to tighten the single lug is beyond the level of hand-tightening and even more than what is required currently on a 5-lug (about 450N, or roughly 100 lb-ft of torque for five lugs, but a center locking requires 650N, or 450 lb-ft). The need of very expensive powerful tools is too much, so that’s why the center-locking is not feasible for street cars.

      • I use a standard 14″ X lug wrench, let’s say is’a 18″ single-arm for arguments sake.

        If that gets me 450N force, W = FD, solving for (Force), 450N/18″=F or 25.

        If we now need 650N, but want to use the same 25 “units” of force (N/inch, ugly, but works for this)
        650N = 25 * D or 26″.

        Increasing the lever arm to 26″ would allow you to perform the same task on the side of the road or in your garage. Small enough that it could still be stored in the trunk in the wheel well or attached to the top of the deck lid.

        I 100% agree with what you said and that’s part of what my question was – “is this even possible” – but if your 450N/650N numbers are accurate, a simple extension to about a 2′ lever arm would be more than sufficient to disengage and re-install the nut.

        • Hilarious video. But it’s got to be easier. I can see a 3′ solid steel bar doing the trick if the numbers @Bobby stated above are accurate.

  2. Thank you! And always glad to have your questions.

    — I don’t think the single lug has been finalized. There was a post this morning from a European racer who noted that they use single lugs and there are still challenges for getting the lug on and straight. I will be looking into it, though!

    — Here’s a surprising tidbit: Many early passenger cars used a single lug. They called it a knockoff lug because it had arms coming out and you knocked them with a hammer to loosen the lug. It is fairly easy to get those wheels on and off… which means they are easy to steal because a couple whacks of a hammer and it’s off. That seems to be one of the big reasons why manufacturers moved away from single-hub wheels in the passenger car domain.

  3. Everything that’s old is new again, eh? Funny how the issue is ‘easy to steal’ – wonder if anyone’s even attempted to address that in a modern world.

    • If you look at the single lug center lock wheels on a Porsche 911 GT3 they require a special socket, its not a standard hexagonal nut. If you look at the nuts on F1 or sports cars its is even more specialized for speed.

  4. It’s a good incremental move. Now I want them to have 6 speed transmissions (but still 3 pedals).

  5. Remember F1 has been using single lug alloy wheels forever. They also hold the record for four wheel pit stop of 1.82 seconds.

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