Strength and Lightness: Installing ARP Wheel Studs and Skunk2 Racing Forged Lug Nuts

Wheels and tires on a race car are, literally, “where the rubber meets the road.” Racers spend hours and hours debating the perfect tire for the perfect lap. But, commonly ignored is how those wheels and tires are affixed to the car. Wheels are attached by lug nuts on wheel studs, and the reason people often ignore these items is that they rarely fail on a street car and thus don’t require much attention. However, on race cars, this is a very different story.

With sticky race tires, big horsepower, big brakes, and aggressive driving, the stress applied to studs and lug nuts will often destroy stock factory components. When these parts fail, goodbye wheel, and hello car accident. It is hard to win a race when you are upside down and on fire. For a couple of Benjamins and a few hours in the garage, you can install stronger, lighter parts to ensure your wheels stay where they should be — on your car.

When you are running a race car at the limit, you are stressing many parts of the car. Any stress coming to the chassis from the roadway transfers through the wheels. This is why proper wheel studs and sturdy lug nuts are so important. Not many things can ruin your day quicker on a racetrack than losing a wheel.

We decided to upgrade the wheel studs and lug nuts on our Double Nickel Nine Motorsports 1990 Acura Integra RS NASA Honda Challenge car. From years of racing, we learned the hard way that stock factory wheel studs are designed for passenger car trips to the store to pick up toilet paper, not to handle heavy curb strikes and wheel-to-wheel racing.

We trust ARP bolts for all of our necessary fasteners, and they have a set of strong chromoly wheel studs for Honda/Acuras. With a simple click of the mouse, all we had to do was wait for the UPS man to show up and we could get to work.

The first step in our project to keep our wheels on our race car was to source the right parts. ARP makes strong wheel studs, sold in packs of four. For our Acura Integra racer, we needed a total of four sets. ARP part number 100-7711 is the exact one required for any Honda/Acura built from 1980 through 2000.

Once we ordered the wheel studs, it was time to source a set of lightweight and sturdy lug nuts for holding the wheels on the studs. For this, we entrusted the folks over at Skunk2 Racing who have tons of racing wins under their belt and have been leaders in the import racing scene for years. There are plenty of lightweight aluminum lug nuts on the market (you want hot pink ones?). However, only Skunk2 Racing makes a set made with forged aluminum which makes them stronger (precisely what we are looking for in racing).

For Honda/Acura fans, Skunk2 Racing sells a set of 16 forged-aluminum lug nuts (one set takes care of the whole car). These lug nuts are stronger and lighter than their aftermarket competitors (and much, much lighter than the stock-steel acorn nuts that came from the factory). Skunk2 part number 520-99-0825 has the correct thread pitch, 12 X 1.50 mm, to match perfectly with our new ARP studs.

Once our parts arrived, we took the time to compare the stock components with our new aftermarket racing components. At first glance, it is obvious the ARP wheel studs are longer, which is an advantage for using different wheels and wheel spacers on race cars. The ARP wheel studs are manufactured from premium-grade, heat-treated 8740 chromoly steel, nominally rated at 190,000 psi tensile strength, and cadmium plated for extra durability.

According to the folks at ARP, “Our studs can easily handle the tremendous acceleration shock loads and lateral forces found in racing applications. Our ARP wheel studs are must-have replacements for competition vehicles.” The ARP wheel studs have a bullnose end which makes it easy to thread on lug nuts during fast pit stops. This design feature assists in not cross-threading a lug nut with an impact gun.

Here you can see how much longer the ARP wheel stud is (top) versus the stock wheel stud (bottom). You can also see the different designs between the Skunk2 Racing forged-aluminum lug nut (top) and the stock steel acorn nut (bottom). The more extended Skunk2 lug nut has more threads in contact with the wheel studs as well as more surface area touching the wheel than the stock lug. All of this adds up to more security.

With the longer wheel stud comes added weight, and racers hate adding weight, especially when it comes to rotational mass. But, we were able to counteract this with the lighter Skunk2 Racing forged aluminum lug nuts. Jeff Giovino at Skunk2 Racing detailed some of the design advantages of its lug nut, “Our Skunk2 forged lug nuts are hard-anodized for superior corrosion resistance and are extremely lightweight.”

“With an industry-leading weight of 23.5 grams, each Skunk2 lug nut helps reduce unsprung weight without compromising strength. Each lug nut also features a perfectly tapered end for maximum wheel-to-lug contact, as well as durable threads for added longevity.” To see if Jeff’s claims on weight were legit, we put their lugs on our scale to compare. He was right on the money; they were super light, which made us very happy at the race shop.

Here is a weight comparison of a stock wheel stud and stock steel lug nut (left) with an ARP extended wheel stud and Skunk2 Racing forged-aluminum lug nut (right). The stock components weighed 0.192 pounds while the stronger parts (ARP/Skunk2) weighed in at 0.185 pounds. Sure, 0.007 pounds may not sound like a lot; however, there are 16 wheel studs and lugs on an Acura Integra which equals 0.112 pounds of rotating mass/unsprung-weight savings, while also being stronger. Losing more than a tenth of a pound on something continually spinning on the car is a win-win.

Once we were convinced the parts we chose were the correct ones, it was time to install them on our race car. In most cases, you will not be able to replace wheel studs without taking the hubs off, so the first step is to remove the hubs. Using our handy, inexpensive Harbor Freight press, we pressed out the stock wheel studs.

With the right tools (a press instead of a hammer) this is a straightforward and quick process. The key to using a press is to ensure your parts are in-line as you press the components out. To find the perfect setup for this takes some ingenuity and creativity. We use equal length sockets to hold things in just the right place to make pressing studs out super easy.

The first step in installing a new set of studs is to delete the existing studs. The best practice is to use a press. Yes, your friends told you it could be done with a hammer, but I certainly don’t recommend it. Use a couple of equal length sockets to hold the hub in place and let the press do the hard work.

Assembly is the opposite of disassembly when it comes to pressing-in wheel studs. An important thing to remember here is which direction to press the studs in. Once a hub has no studs in it, it isn’t always obvious which way the studs go (until you do it wrong and try to re-attach the hub to the car). Our recommendation is to mark the hub “outside” with a magic marker before you start pressing-out studs. The ARP studs, which are manufactured with extremely accurate tolerances, pressed into our Acura hub perfectly.

Once the old studs are pressed out, it is time to flip the hub over and press the new longer-and-stronger ARP studs in place. The key here is to press the studs all the way down until they are flush with the back of the hub. But, don’t press so hard that you warp or damage the hub. If you make this mistake, you are buying a new hub assembly.

With our studs pressed-in and the hubs re-attached to the car, we took the time to inspect the match between our wheels and our new Skunk2 Racing lug nuts. We use lightweight Enkei RPF1 wheels and wanted to ensure the tapered edge of the lug nut mates correctly with the wheels. The match was right on.

What we liked about the Skunk2 Racing lug nut was the amount of surface area at the tapered edge that contacts the wheel once the lug nut is torqued down. We also liked the large number of threads mating to the stud. Both of these features will provide more strength in the wheel attachment.

It is essential to check the mating surfaces between your lug nut and wheel. If the taper is correct, then you will have the right amount of surface area from the lug nut against the wheel. Check this, by placing the lug nut on the wheel when it is off the car, and the stud is out of the equation.

The ARP studs and Skunk2 Racing forged-aluminum lug nuts allow our team to use a higher torque value for attaching the wheels to the race car. If we tried to torque our wheels at 100 foot-pounds with a stock stud, there is a good chance we would strip the threads or break the stud.

With the 8740 chromoly ARP stud mated with the 7075 forged-aluminum Skunk2 Racing lug nut, we can have confidence the hardware can handle the torque specs needed for racing. As a standard practice, we torque our lug nuts after every session on track to ensure we don’t lose a wheel. We also keep a box filled with spare lug nuts and tools to clean the threads inside of a lug nut or the threads on a wheel stud for emergencies.

Because of the number of wheel changes we do during pit stops, we always keep a good amount of spare lug nuts in our trailer. We have a small box with extra Skunk2 Racing lug nuts, a thread cleaner with the same thread-pitch as our wheel studs, and the perfect size socket for the thread-cleaner tool. This allows us to maintain our studs and fix a problem quickly during a pit stop.

We bolted our wheels onto our Honda Challenge car and torqued them down to our specifications. We drove the car around and then re-torqued again to ensure our wheel studs were pulled-in all the way. Once we knew everything was set, we headed to the track and put some hard miles on the new studs and lug nuts. Good news! A wheel didn’t fall off!

The forged lug nuts and chromoly wheel studs give me a lot of confidence when I am running the car at the limit. There are plenty of things to worry about when racing, losing a wheel should not be one of them. Ensuring you have the correct hardware in place means you can drive hard and not worry about this sort of thing. Metallurgy is everything. If you want to nerd out on metallurgy and learn all kinds of things about metal brittleness, check out the technical information from ARP here.

Here is the final moment, a fresh set of robust ARP wheel studs with Skunk2 Racing forged-aluminum lug nuts. This setup is sturdier and lighter than stock as well as our previous lug nut selection. Durable and light is precisely what racers are looking for — time to head back to the track and win more races.

Swapping out wheel studs and changing lug nuts is an easy project and one I recommend to anyone taking their car to the track. Regardless if you are a wheel-to-wheel road racer, an autocrosser, or an HPDE/track day fan, adding performance tires and running around a racetrack will put stress on your car beyond that of the manufacturer’s design. Be smart and upgrade. In my opinion, this modification is a no-brainer.

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About the author

Rob Krider

Rob Krider will race absolutely anything. He is a multi-national champion racing driver and is also the author of the novel, Cadet Blues.
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