Back to the Basics: How to Torque Lug Nuts
6/21/2002
By: Scott Croughwell
Los Angeles has the dubious honor of being the one city in the United States with the heaviest automotive traffic. Average Angelinos sit in traffic an average of 124 hours per year; thus, we’ve thought of many things to do during that slow crawl home on the 405 freeway. On a particularly nasty traffic day, one of the Overboost Staff members saw someone – an apparent sport compact car enthusiast, by the looks of the vehicle – trying to change their tire on the side of the road. “It was hilarious,” our Staffer tells us. “He had the car jacked up and the tire spun round and round while he tried to loosen the lug nut!” Loosening lug nuts doesn’t really cross the train of one’s though often. So, here we go.
Removing the wheel from a car begins with loosening the lug nuts. Then jack the car up. Even if you can apply the parking brake to hold the wheel still while you loosen, always loosen (or tighten) lug nuts with the vehicle on the ground, so you don’t twist the car off the jack. Most sport-compact cars have four lugs, so loosen the nuts in a “star” pattern in the 12:00-6:00-3:00-9:00 o’clock positions. You don’t have to remove the nuts; just loosen them, then jack up the vehicle.
It’s commonly misconceived that lug nuts do 100% of the support work when it comes to holding the wheels to the vehicle. Thankfully, this is not true. Wheels are “hub centric”, meaning that the “center” of the wheel is what does the holding. The lug nuts merely provide clamping force. A properly torqued lug nut will provide over 10,000 pounds of clamping force – per lug.
Properly torquing a lug nut is a simple thing. If you caught Basic Toolbox or Bolt Tech, you may have noticed our stress on the importance of having access to various torque wrenches. And since torque wrenches can only measure bolt clamping force indirectly (by measuring the torque applied to the bolt) it’s important to keep everything bolt related, clean. Don’t use any type of lube or anti-sieze, as this will make it easy to overtighten the nuts. The hub, hub face, wheel studs (or wheel bolts, if you drive German) and lug nuts should all be kept immaculate. This may seem excessive, but unevenly torqued lug nuts apply uneven clamping loads to brake rotors, causing them to warp and leading to brake shudder.
To ensure best brake life and performance, always loosen or tighten lug nuts in a criss-cross pattern. With four lug cars, use the 12:00-6:00-3:00-9:00 o’clock routine outlined above. With five lug cars, you will literally be using a “star” pattern as depicted in the photograph above.
Once everything is clean and you’re ready to slap your wheels back on, thread on the lug nuts (or lug bolts) and hand-tighten. You can see that we’re also giving the nuts a light tightening with a wrench. Stress, light tightening. Once that’s done, you can slowly lower the jack and grab your torque wrench.
Most auto manufacturers specify lug nut installation torque at 65 to 90 foot-pounds; we usually torque in the middle at 75 to 80 foot-pounds. Remember, the lug nut merely provides clamping force, it does not hold the wheel centric to the hub. Even if you use the minimal torque spec of 65 foot-pounds, you’re still getting about 9,500 pounds of clamping force per wheel. Sometimes, less really is more.
