It’s fine to use a pneumatic impact wrench to run the nuts up onto the studs, but always use a calibrated torque wrench for the final tightening procedure. Photo: Jim Park
A Wrong and Right Way to Mount Truck Tires
One seldom sees the words tire service and finesse in the same sentence, but proper mounting and installation of tires and wheels requires skill and precision — and indeed, a little finesse.
It’s one thing to wrestle the tire onto a wheel, air it up, and mount it on the truck. It’s quite another to make sure it’s concentrically mounted, the hub mounting face and the disc face of the rim are clean and rust-free, and the fasteners are properly torqued. Watch the folks servicing your tires to see if they are doing all this. If not, here are five things you might want to remind them are necessary for secure mounting, long tire life, and tire and wheel installer safety.
Tire mounting
Inspect the rim for signs of damage, distorted shape, excessive corrosion, or any damage or irregularities in the rim bead seat, including rim flange wear. Carefully examine the wheel for cracks and worn or distorted stud holes. The mounting face of the disc wheel should be thoroughly gone over with a stiff wire brush to remove any rust, flaked metal, old paint, dirt and debris, etc. so it will fit flush against the mounting face of the hub.
“Any contacting surfaces must be absolutely free of any material that can be compressed as the clamping force is applied,” says David Walters, manager of warranty and field service at Arconic, makers of Alcoa wheels. “Paint, rust or dirt will eventually wash away or fall out, reducing the clamping force. In particular, steel wheels that are painted are most susceptible. Corrosion of the steel and old paint can flake away.”
If the tire has a colored balance or runout dot on the sidewall, determine the meaning of the colored dot and mount the tire on the rim accordingly. Typically a yellow dot will align with the valve stem while a red dot will align with the dimple on steel wheels, but some tire makers use different colors.
With the rim and tire flat on the floor, apply a bead lubricant to help seat the tire. Never use a flammable liquid such as starting fluid to seat the tire bead to the rim. Inflate the tire to a minimum pressure to seal it and keep it in place on the rim.
Once the tire is firmly seated, check to see that the distance between the rim flange and the aligning ring is uniform around the complete circumference of the tire. With the bead seated against the rim, the distance from the seating ring to the rim should be measured at four different points that are 90 degrees apart around the rim. The distance between the ring and the rim should be the same at all four points.
“Ensuring proper bead seating when mounting tires ensures optimal performance and tire life,” says Scott Green, B2B CES manager, Michelin North America. “An improperly seated bead creates uneven wear patterns and increases the chance for ride/vibration issues.”
Tire inflation
Technicians should verify the desired inflation pressure with either the tire manufacturer’s load and inflation table or the fleet’s preferred inflation pressure, usually based on tire type and wheel position. Before the tire is inflated, it must be rolled into an inflation cage for the safety of the installer and everyone else in proximity to the tire.
“Using certified and approved air-up safety cages, clip-on air chucks and calibrated regulators are a must,” says Bob Eck, TA Truck Service Commercial Tire Network vice president. “To provide added assurance that the casings will not rupture, allow 20 minutes at maximum pressure before the removing tire from the safety cage. There are no guarantees, however, since you cannot see what’s going on inside the tire during the inflation process. When using external cages, you can reduce the chances of injury by following proper procedures and keeping a safe distance from the tire.”
Wheel mounting
As with the mounting face on the wheel, ensure the hub mounting face is completely clean of old paint, rust, dirt, and other debris. Next, check and ensure the studs are not damaged, stretched, or badly corroded. The threads should be in good condition, have no paint or contaminants on them, and be the correct length and diameter for the type of wheel (aluminum or steel). The threads must match the nuts, e.g., metric or English sizing.
If you have to replace a damaged stud, the two adjacent studs should also be replaced. If you have two or more damaged studs, all 10 studs should be replaced with new hardware of the correct size and grade for the application.
“You do not have to replace all the studs each time you do a wheel installation,” says Brandon Uzarek, field engineer for wheels at Accuride Corp. “Good quality studs will last a long time, provided they have not been stretched or damaged. I have seen examples where you can rub the thread from the stud with your thumb. Studs like that obviously have to be replaced.”
Make sure there is no wear or damage to the hub pilots that would prevent concentric mounting of the wheel on the hub.
Stud fastening
Before installing the nuts, place two or three drops of motor oil on the clean threads of the studs and one or two drops of motor oil between the washer and the nut on the two-piece flange nut. This reduces friction and allows you to achieve a desirable clamping force once the wheel is torqued down.
Ensure the two-piece flange nuts are in good condition and not seized between the nut and the flange. Run several nuts onto the studs using two or three drops of oil on the stud and between the washer and the nut on the two-piece flange nut. Use three or four nuts at light torque to hold the wheel in place on the hub and check for concentric mounting of the wheel on the hub. This will display as a high and low spot when rotating the wheel. Resolve the runout problem before installing and torqueing the remaining fasteners.
When mounting a pair of wheels in a dual assembly, ensure the diameter of the two tires is identical. Even a tiny difference can result in excessive scrubbing of the tires, causing premature wear.
Wheel nut torqueing
Verify the correct torque requirements for the wheel being installed. The Technology & Maintenance Council’s Recommended Practice 237A, Torque Checking Guidelines for Disc Wheels, shows torque fastener recommendations ranging from 300 to 900 ft-lbs., depending on the wheel type, fastener, and procedure.
“Always use calibrated torque wrenches to torque lug nuts to manufacturer-recommended specifications,” warns Eck. “Following manufacturer’s recommendations on proper torque will reduce the chances of a wheel-off and vehicle damage.”
Finally, check to ensure there is no side-to-side movement of the rotating assembly. Once the tire is installed, a runout gauge should be used to confirm the trueness of the wheel assembly.
If it’s not true, “its effect is to lead a vehicle alternately left and right as it rolls along, creating the perception of a shimmy or wobble,” says Green. “If it’s not running true, something is amiss. Don’t ignore this area. If you do, expect problems down the road.”
The final step in the process is to retorque the wheel nuts somewhere between 50 and 100 miles after a wheel has been installed. This is important because the wheel will settle into place during this period. Foreign matter may work its way out of the mounting surfaces, causing a loss of bolt tension and a loss of clamping force.
Installing tires and wheels isn’t all brute force, or at least it shouldn’t be. The final check and adjustment will help reduce irregular wear and possibly prevent a wheel separation. Both are well worth taking a little extra care during installation.
by Jim Park
Source: https://www.government-fleet.com
I´m a Fleet Management expert, and the manager of Advanced Fleet Management Consulting, that provides Fleet Management Consultancy Services.
