Wheel Lug Nuts

Keeping the Wheels Attached to the Car

or

More Than You Want to Know About Lug Nuts

The single largest concern here is that you have adequate engagement between the lug nuts and wheel studs. The picture above is what you shouldn't have. Notice how the studs don't stick out past the lug nuts. These wheels studs are simply too short. This might very well be a good example of where the engagement between the nut and stud is marginal. This is not a good thing.

The general rule is that the number of engaged threads should equal the diameter of the wheel stud. In other words if your wheel stud 12mm in diameter than the lug nut should engage at least 12mm of thread. 

The Southern California Timing Association, which governs the racing at Bonneville, requires at least 5/8 inch of thread engagement.  The SCTA also prohibits the use of closed-end lug nuts. 

This Mustang is a great example of closed lug nuts. We simply don't have a clue about what's going on with closed lug nuts. It's difficult to see how many threads are actually engaged. A worse case scenario though is where the wheel stud bottoms out on the inside of the lug nut which would lead you to believe you're tightened the wheel properly. 

Even though you tightened the wheel (so you think) the wheel would still be loose on the hub. Most sanctioning bodies simply don't allow this sort of lug nut. Since this is a Mustang running an SVRA vintage race we have to assume someone messed up. SVRA is usually pretty good on safety standards.

This is the way your race car should look. While it might seem the studs are a little long that's simply not a problem. It may look a little strange but these longer studs make it easier to put the wheel in place on the hub and there's no problem with having a little too many threads showing. 

We never think about wheel studs and lug nuts. They just exist. When you start changing the wheels around on your car you really need to pay a little more attention to these items.  The wheel above might be a good example of how it should be done. 

Notice in the Porsche wheel above that open wheel nuts are used. Even more important they're made out of steel. The stock Porsche 911 lugs nuts are made from aluminum and have a closed end. Most race sanctioning bodies won't let you use the stock Porsche lug nuts.  They require that you use this type of steel lug nut.