To rotate tires or change a flat tire, you need to know how to tighten lug nuts, but “tight enough” isn’t enough. While many people get away with using a spider wrench, breaker bar or impact gun (which could be disastrous), the best way to tighten lug nuts is with a torque wrench. Here’s how to tighten lug nuts the right way.
What Is Torque?
Wheel studs and lug nuts clamp the wheel, brake rotor and wheel hub together, which transmits braking torque to the wheel on deceleration and drives torque from the engine and transmission. Automotive engineers design wheel studs and lug nuts to achieve a specific clamping force or bolt tension.
Professional and DIY mechanics can’t measure clamping force or bolt tension. Instead, they use torque, a measurement of twisting force, to determine the correct clamping force. When torque is applied to the lug nut, it’s converted to linear force, which stretches the wheel stud and clamps everything together.
For example, a lug nut torque might be 76 foot-pounds, which is 76 pounds of force applied to a one-foot-long lever. Using a torque wrench that’s 3 feet long, you can use only one-third the force, or 25.3 pounds, to have 75 foot-pounds of torque. Newton-meters, kilogram-meters and inch-pounds are other common torque units. Because the torque wrench is set to click, beep or vibrate at a specific torque value, the same torque can be applied to all the lug nuts, resulting in even clamping force.
How to Tighten Lug Nuts the Right Way
Tightening lug nuts the wrong way can cause problems, some of which may not be immediately noticeable:
- Undertorque could result in losing a wheel.
- Overtorque can stretch the wheel stud, possibly breaking it, or distort the brake rotor or wheel hub, causing vibration or pulsation.
- Uneven torque (each lug nut torqued differently) can cause vibration or pulsation.
After setting the torque wrench to the specification in the owner’s manual or repair manual, there are three steps to tighten lug nuts properly:
- Replace damaged studs or nuts.
- Use a wire brush to clean the wheel stud and lug nut threads, and then dry them. Corrosion, thread damage and oil or grease can skew torque application and affect clamping force.
- Clean the wheel, hub faces and the center hole with a wire brush as well, then dry them.
- Apply a dab of anti-seize lubricant in the center hole if necessary, but do not apply to the wheel studs or lug nuts.
- Run the lug nuts in with your favorite tool until snug, but no more.
- Tighten the lug nuts in a star pattern twice, smoothly applying force until the wrench clicks, but no further.
Knowing how to tighten lug nuts properly is critical. Keeping your wheels on helps you and others on the road to stay safe, and setting proper torque prevents damage to the wheel, hubcaps and disc brakes.
Check out all the hand tools available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on lug nuts, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photos courtesy of Benjamin Jerew.
Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.