Back to Basics – Part 2

Building on the knowledge gained from last month’s column on wheel measurement basics, let’s take a look at the different types of lug nuts and their purposes.

This may seem like a trivial matter, but the fact is that for all of the work that you do in your shop, a fifty cent piece of metal can cause a lot of misery and liability concerns.

First, the more common lug nuts used in the aftermarket are the acorn or conical seat lugs which typically have a 60° angle. Beware, some manufacturers use a 63° angle on some of their tuner-style wheels. Acorn lug nuts come in two distinct designs. One has a 13/16-inch hex and is straight from top to bottom, while the other has a 3/4-inch hex with a bulge at the base before the angle begins.

Make sure that when you replace lug nuts that the customer’s own lug wrench will fit properly on the new set. Many times, this is overlooked, and will create an upset customer if he/she can’t change a flat tire in an emergency.

Also, if you sell custom wheels that require a thin wall socket to reach the lugs, make sure that it’s compatible with the customer’s lug wrench, as well. If not, you’ll have to make sure he/she can acquire the right wrench for a nominal cost.

Beware of Long Studs
In the last few years, the automotive industry has seen more changes in bolt circles and thread pitches than in the last 20 years combined. One major problem that has cropped up for dealers is the increased length of lug studs. This means that a standard length lug nut will bottom out before fully applying the proper seat pressure against the wheel.

The problem is that you may not notice. The wheel may look tight, but in actuality it’s ready to come off as soon as the customer drives away. The solution here is to use duplex length lug nuts. These are available in both hex sizes and are approximately 1/2-inch longer than standard. Typically, the bulge head lug nuts are needed for aluminum wheels with deeper lug holes, but can be used on steel wheels as well.

Next, we have the mag shank lug nuts. These lug nuts are available in multiple lengths depending on the application. Each requires a washer, either separate or built-on, to apply the proper seat pressure and keep the lug nut from scarring the face of the wheel.

The most common are the short shank, standard shank and extended shank (see Diagram 2). There are other lengths, but these are the most commonly seen by dealers.

Mag lug nuts for aftermarket wheels are typically designed for vehicles that were built 20-30 years ago. This means that most new thread pitches are not available in a mag shank lug. The exception is the 14mm x 1.5 common to the 1988-98 GM 1/2-ton 2WD trucks. The wall of the shank was too thin to have any strength, so the wall was thickened and it became a duplex.

Keep in mind, these will not fit old style wheels that accept three different bolt patterns. Certain wheels, like the Cragar S/S, were modified – the lug hole was enlarged – to accept the 14mm lug. This means that a Cragar S/S that came off of a pre-1988 GM 1/2-ton 2WD will not work on a 1988-98 truck.

Washer Differences
While we’re on the subject of mag lugs, let’s talk about the different washers needed for some common applications (see Diagram 3). Washers are either centered or offset, depending on the application. Cragar-style washers are thick and are usually chrome plated, while Keystone Klassic washers are thinner. The offset washers are used on vehicles with either a 5-4.5 or 5-5 bolt circle. The center-punched washers are used on vehicles with a 5-4.75 bolt circle.

Next, let’s look at the larger duplex and dualie lugs. Make sure that when you order lugs for 3/4- and 1-ton trucks that you have the proper length lug nut. Ford F250 and F350 trucks from the mid-1980s to late-1990s require XXL length lug nuts. Also, some dualie wheels require special lug nuts, such as a 90û acorn or a washer either built on or separate.

Next, we have the ET mag lug nut. This is an acorn lug nut with a small shank on the end. These lug nuts are of great use to help center a wheel onto the lug studs.

Aftermarket wheels are not typically hub centric like the factory wheels. On occasion a vibration will occur in a front-wheel drive vehicle, and using these types of lugs and a centric ring, which we’ll discuss in a future article, will help eliminate the vibration (see Diagram 4).

Our last major type of lug nut is one of the newest (see Diagram 5) on the market. The socket lug or "Tuner" lug is a very narrow lug nut that will just barely fit into the lug hole of a tuner-style wheel. They are available in several colors and in chrome.

These lug nuts are installed with a key that engages the lug nut through the center instead of the outside of the lug nut.

It is recommended that you torque these types of lug nuts by hand, as too much abuse from an impact gun can lead to the key wearing out or, in some cases, breaking.

A word of caution regarding these socket lugs – make sure that the lug studs on the vehicle aren’t too long or the key will be pushed out of the head of the socket lug, making it is almost impossible to torque the lugs properly.

Next time, we’ll discuss different types of wheels, different types of finishes and the proper maintenance of each.

Until then, remember to torque those lug nuts properly!