AKRON (June 7, 2004) — Sure, chasing the big wheel/tire craze can mean big profits. But not paying attention to those seemingly little things—like proper wheel bolt tightening—can mean big headaches (or even worse) for tire/automotive technicians.
With some auto makers fitting consumer vehicles with 17-, 18- and 19-inch wheels, and aftermarket wheels pushing well into the outer limits of 20, 22, 24 and even 28 inches, the conscientious professional will make sure the correct parts, tools and procedures are followed.
Read how some of the leading players in the industry approach the decidedly non-glamorous arena of wheel fastening, then take an inventory of your operations.
“If anybody's been in the tire business and they say they never had a wheel fall off or come loose, they're lying to you,” said Barry Steinberg, owner of Direct Tire & Auto Service in Watertown, Mass. “We install the lug hardware using an air gun and torque sticks, but ever so gently. We tighten them slightly with a low pressure. Lower the car. Start at the left front tire and hand-torque them, ending up at the left rear.”
Direct Tire purchases wheel torque charts every year from the Tire Industry Association (see sidebar, page 26) and pays close attention to the specialty hardware that can come with the wheel. Generally, “the wheel manufacturers don't really give you a lot of information,” he told Tire Business.
“A loose wheel can damage a hub, damage a car, damage a life. All of my technicians have their own tools. We help finance them. A tire tech is as obligated to have as good tools as a front-end technician.” The torque wrenches cost $200 to $300 and are recalibrated about every six months.
“Like any piece of equipment, it is a wear item,” Mr. Steinberg said, and dropping a torque wrench can result in errors of five to eight pounds.
“Before you drop the car down, you should spin the tire and make sure the wheel is seated properly on the hub or the drum,” he advised. “There could be rust built up. We'll look at the mounting surface and take the necessary action to ensure there's a real good contact between the wheel and the drum.
“You have to be as careful with a Honda as a Ferrari,” Mr. Steinberg said. “They're all loaded guns if you're not careful.”
Mel Dobrin, president of Butler Tire Co. in Marietta, Ga., said torquing is mandatory on all custom wheels—and always with a torque wrench, not an impact gun. “We at Butler Tire do not use any air wrenches—even with color-coded sockets that do not allow for over tightening of wheel lugs. We find the hand torque method safer and more accurate.
“If we are installing 20-inch wheels and tires on a Mercedes, we go through all the motions of force variation, on-the-car balancing, world-class quality tires and wheels. So as far as I am concerned, you need hand-torquing to finish.”
At Butler Tire, the rule is that all cars, light trucks and sport-utility vehicles with alloy wheels, whether original equipment or custom, get hand-torqued. Mr. Dobrin said this can prevent the over-tightening of one or two lugs that may “cock” the wheel assembly and cause vibration problems.
Today's extensive use of aluminum wheels poses a potential disaster for shops that overdo torque, noted Bruce Nomura of Nomura Tuning and Design. The Tracy, Calif., builder of high-performance street and show vehicles said that even if the studs don't snap, strip or stretch (noticeable by bottle-necking of the shaft or thread spacing) during installation, the higher expansion rate of aluminum wheels as the vehicle is driven and brakes are operated can cause the wheel fasteners to break suddenly.
Pointing out that impact guns can deliver well over 600 foot-pounds of torque, Mr. Nomura said it's easy to use excessive force. “There's a tremendous amount of stress. When the wheels expand, the lug nuts can pop right off.”
Meticulous tightening is also critical with minivans, he added. “If you don't evenly torque these wheels down, they tend to warp the rotors. As you use the brakes—especially on the minivans because they're so heavy—the expansion and cooling down is dependent on the pressure of the lug nuts. With their greater weight and front-wheel drive, minivans are especially prone to rotor and drum warpage caused by over-tightening.”
Mr. Nomura also pointed out that lug nuts are used to clamp the wheel to the hub; they shouldn't be depended on to align the wheel and tire assembly onto the hub.
“The biggest complaint from customers is vibration,” he said. “People constantly bring their tires back. They'll have had the tires rebalanced, but they're still complaining. They'll want a wheel alignment, but provided you balance the wheel and tire properly, vibration's never about alignment. I see this problem all the time. Shops can save a lot of money and a lot of time if they make their employees aware of this.”
Many wheels are “hub-centric” in order to position the wheel properly. Some aftermarket wheels—especially those made in Japan—are designed to allow spacer rings of varying thicknesses. “Those rings are very important, particularly the greater the size of the wheels,” Mr. Nomura said. “I've seen a lot of shops throw those rings away. If the inside diameter of the wheel mount does not fit the outside diameter of the hub, you're in trouble.”
He also cautioned workers to note whether the wheels have rounded or tapered seats.
“That's a commonly missed difference that can be serious. The wheel isn't properly held down and because of that, they tend to come loose,” he said.
Russ Worsley of Ken Towery's Auto Care Centers said the Louisville, Ky.-based business is always on the lookout for wheel and hub corrosion. “Not only can it make the wheels difficult to remove from a vehicle, (but) they can make the wheel seat improperly, possibly damaging the wheel or vehicle,” he said. “Torque can also be affected by rust and corrosion. The studs, lug nuts and wheel/hub mating surfaces must be clean in order to get a good seat and the proper torque.”
Aftermarket wheels installed at the company's Ken Towery retail tire shops are hand-tightened using a ½-inch drive, “clicker-type” torque wrench, he added.
Bob Pond of Central Tools Co., a Cranston, R.I.-based manufacturer of torque wrenches, agreed that the torque specifications for wheel lugs are for wheel lugs with clean, dry threads. Anything else will affect the accuracy of the clamping force, he said.
“Also, when using the wrench, the user needs to apply slow steady force to the handle of the wrench without 'bouncing' or applying force after the click,” he instructed. “They also need to be sure that the fasteners are tightened evenly so as to be sure that the wheel fully seats against the hub face.”
Recognizing that scratches and dings are somehow even more painful on wheels that can carry four-figure price tags, manufacturers have devised new fasteners.
“We've seen the advent of the spline-drive and socket-lug type lug nuts in the past several years,” Mr. Worsley said. “These allow more lug pocket clearance in aftermarket wheels. More clearance minimizes damage to the wheel's finish.”
Venerable custom wheel manufacturer American Racing Equipment Inc. of Rancho Dominguez, Calif., together with the McGard Co., has been employing what it calls “tech drive” lug nuts. This is just another example of the tuner market segment driving style, explained American Racing's Todd Badger, eastern sales manager.
“Socket-style lug nuts were first in the market. These are an open-ended style lug nut that offers a 'tuner look' or a 'racing-style' look,” Mr. Badger said. “Tech drive (spline-style) are closed-ended, which helps prevent surface rust from collecting on the stud and lug engagement area.”
Form doesn't necessarily overshadow function, he said. Together with partner McGard, American Racing offers a spline-drive lug for consumers willing to pay for quality.
These high-end fasteners, Mr. Badger claimed, offer 26 percent more seating surface space, 34 percent more stud engagement and 59 percent more positive engagement in drive design, and are 30 percent lighter compared with conventional “open” lug nuts.
Still, the best and the brightest designs are effective only when used—and used properly.
Proper wheel mounting, said Frederick Wong, a Los Angeles mechanical engineer and former drag racer, “is the practical application of the basic principles of threaded fastener machine design and classical topics such as initial preload, induced clamp load, stretch modulus of elasticity, centroid of bolt groups, proof load fatigue, preload torque and centrifugal bearing shear.
“The irony is, how many mechanics or custom tire/wheel dealers actually go through the routine of torquing the wheels to recommended torque specifications, following the proper bolt pattern sequence?” Mr. Wong asked.
“Not even the OEM car dealers enforce this,” he added. “Recently, I saw both custom and factory alloy wheels put on a Corvette and an Infiniti FX 45 by mechanics using impact wrenches and going in a circular pattern in one shot.”