A lug nut (or wheel nut) is a nut with one rounded or tapered end used on steel and most aluminum wheels. Lug nuts are installed to secure a wheel to threaded wheel studs and thereby to the vehicle axles, there are 4 common types of lug nuts:
- Cone seat
- Bulge cone seat
- Flanged Swivel
Lug nuts must be installed in an alternating pattern, referred to as a star pattern, this ensures a uniform distribution of weight across the wheel mounting surface. It is highly recommended that you tighten them with a calibrated torque wrench, you can use a socket or impact wrench, but the final tightening should always be done with a torque wrench. Torque specifications vary depending on the vehicle and wheel type, manufacturers provide recommended torque values, which should always be adhered to during installation, after installation you should re-torque after driving the vehicle for 50 kms. Improperly torqued lug nuts can result in:
- Warped brake rotors
- Damage to lug nut seating surface
- Wheel hub damage
Below is a general torque specification chart, lug nut specifications call for clean threads that are free of dirt, grit, etc. If applying a lubricant, it must NOT be used on either seat of the hardware as the seat is the main point of friction where torque is measured. When tightening the lug nut, it is important to remember that tight is good, over-tight is NOT good. Over tightening can stretch the stud and cause failure around the rotor, this is why it is so important to be aware of the manufacturer’s specifications. The proper way to tighten a lug nut is to use a torque wrench to torque every lug nut to the recommended specifications. When you over-torque the lug nut you could cause stress fractures and this makes it no longer certified for the load rating, there is a risk of the lugs breaking under normal conditions and your wheels will pass you in traffic, rare, but it does create a safety concern.
There are a few different types of torque wrenches on the market, the most common being the click type torque wrench, you simply turn the wrench handle until it reaches the torque mark you want, then start tightening the nuts. When the set torque is reached you will feel a click around the head of the wrench. There is also a dial type of torque wrench, it has a little meter on the handle, and you will see the torque getting higher and higher while you apply force. Some dial torque wrenches come with an electronic meter on the handle which allows you to read the exact torque. The general rule for steel wheel lug nut torque is usually around 80ft/lb, and for aluminum wheels it is around 100ft/lb, this being said you still need to check on the manufacturer’s specifications.
Drive safe and secure, get your wheels checked.