Editor’s Note: For the next few months, we’ll be sharing weekly lessons that are hard-earned from nearly four decades of garage experiences, exasperations, and general mayhem that either we’ve experienced personally or have been associated with through friends’ miscues. The title intones that most of these errors and screw-ups could have been easily avoided had we been paying attention to the details. So rather than suffer a similar fate, we offer up these lessons learned — the hard way.

Don’t Get Shanked

Many types of aftermarket aluminum wheels use what are called shank lug nuts. These lug nuts place this shank through the main part of the wheel. Through the years, there have been several different lengths of shank lug nuts. What can and often happens is that the length of the shank is slightly longer than the thickness of the wheel. This can be caused by using either the incorrect shank nut or sometimes because of a too-thin washer. This allows the lug nut to bottom out on the hub or axle mounting stud instead of creating a clamp load on the wheel.

With shank type lug nuts, always make sure the shank portion does not protrude past the wheel mounting flange as this will prevent full clamp load on the wheel.

With a reduced or near zero clamp load on the wheel, the wheel is allowed to move in relation to the studs. This can quickly shear off the lug studs. That makes for a very bad day.

For example, let’s say you just bought some new lightweight aluminum wheels for the rear of your street/strip car and they appear to be the same depth as your previous wheels so you don’t check the shank depth. The lug nuts are torqued but the shank length is slightly longer than the depth of the wheel. With a reduced clamp load, each time you jump on the throttle, the wheel creates a sliding motion against the studs and it won’t take long for the studs to fail. Imagine the damage as the wheel departs the rear axle mounting flange and tears up the wheel well as the wheel and tire depart the rear wheel well. If this happens at speed, it could be very ugly and potentially flip the car. You don’t want to be that guy.   

Take the time to inspect all the shank lug nuts to ensure the depth is at least ¼-inch shorter than the thickness of the wheel. This allows the aluminum to collapse slightly and still not bottom out the lug nut shank on the mounting flange.

Thick wheel washers re often used with shank style lug nuts. Many washers are of a slight concave design. The concave portion should always face the wheel. This design is used to maintain a load on the lug nut. This washer is stamped Wheel Side.

Just as dangerous is using a shank lug nut that is too short for the application. The standard rule for any fastener application is that the shank style lug nut must engage a minimum number of threads that equal the diameter of the stud.

For example, with a 7/16-inch stud, the lug nut should engage the stud with no less than 7/16-inch to ½- inch of threads. On a 7/16 x 20 stud with 20 threads per inch, the lug nut should engage a minimum of 10 threads in order to ensure proper clamp load. If the lug nut does not engage a sufficient number of threads, the stud, lug nut, or both could potentially fail.