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 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.

: 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.

: 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

: 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.

: 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.

: 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.

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.

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.