Solid contact

| October 05, 2005

This photo shows what happens when a tire is run flat. This tire actually came completely apart due to heat and fatigue.

Imagine that instead of driving the next 500 miles you had to walk it in ill-fitting shoes with holes and uneven soles that caused you pain every step of the way.

Now think of your tires as your rig’s shoes.

Of all the moving parts in your tractor and trailer, only your tires touch the road. So it just makes sense to ensure that the tires, and the wheels they’re mounted on, stay in good shape.

Changing a wheel or having a tire serviced sound simple, but they’re jobs that involve precision.

Changing a wheel on your truck can easily lead to a wheel off if you don’t know how to perform every step. Also, truck wheels can run almost forever, which means they are subject to deterioration. They need periodic inspection and must be replaced when damaged.

We visited the Wingfoot Commercial Tire Systems center in Levittown, Pa., where Jeff Moyer, the lead technician, showed us how wheels are changed and tires are serviced. Don Nelson, Wingfoot regional director, offered additional help and advice.

You’ll need adequate tools to change your wheels. These include hydraulic jacks and jackstands, as well as a torque wrench with a long handle rated to at least 475 pounds-feet. It’s best to use an air gun with impact sockets to work those tight lugnuts and studs off.

Special tire-handling tools, sometimes called “spoons,” are needed to work the beads on and off the rims, and you’ll need a device that uses a blast of air to seat the beads.

Inflation
Keeping inflation pressure at the correct level is by far the most important aspect of tire maintenance. Truck tires typically run 95-105 psi. Check your owner’s manual for the correct pressure. Use a good tire gauge that is properly calibrated.

It’s the air pressure that supports the vehicle, not the tire itself, which is mainly an air bladder like the air springs on your suspension. Unlike air springs, tires that are underinflated overheat badly because of the excess flexing of the sidewalls. The belts may flex enough to suffer fatigue, too, according to Steve Boone. When properly inflated, flexing is minimal and tires run quite cool. The tread also squirms less, prolonging life and improving fuel economy.

Changing a wheel
It’s best to carry all the necessary tools along with you, including, especially, the right torque wrench. It really helps to have along an air-powered impact wrench to get those lug nuts off, too. Many drivers figure out a way to connect their air guns to the brake system air supply near one of the air storage tanks.

Even if you can’t carry enough tools to do the job yourself, if you get roadside assistance, make sure the service technician does the job as we describe it. If he does not, have the wheel mounting checked by a competent service outlet at the next available opportunity.

  1. The first step is always to place a chock both behind and in front of a wheel. Working on a level area also helps guarantee your safety.

  2. Use a good, portable hydraulic jack rated for your vehicle’s weight to raise the vehicle. The best place to use in raising the truck is under the axle, since it is obviously designed to support the truck adequately.
  3. Hydraulic jacks work best near the bottom of the stroke of the cylinder. Adjust the height of the jack so it is within 1 inch of the axle to avoid overextending the cylinder. This is done by screwing the adapter upward as necessary. If the jack is far below the axle, you can switch to a taller adapter.
  4. Place the jack squarely under the axle. Make sure it’s not off center and that it’s on a hard, flat surface. Close the valve by turning clockwise and then pump the handle until the bottom of the tire is a couple of inches off the ground.
  5. Then place a jack-stand squarely under the spring in case the jack should fail to hold the truck in position. Adjust the height of the jack-stand with the through-bolt so it’s as close as possible to the spring.
  6. Loosen the lugnuts in several stages, going in a star pattern. Check the frame rails for an illustration of the specific pattern you should follow, as some truck manufacturers provide this. In general, start anywhere you want, but after loosening one about 1/4 turn, go to the one directly across from it. Once that is loosened a quarter turn or so, jump back across the wheel to the one next to the one where you started. Keep going back and forth across the tire this way, loosening each a little at a time, until all the lugs have been loosened, in several stages, to the point where they can be turned by hand. It is necessary to take the tension off the wheel in this way to avoid warping it.
  7. When you have removed all the lugs, use some sort of leverage to support the tire while you slide it outward and off the lugs. You can use a simple bar, or any of various kinds of tire handling levers. You need to support the tire with leverage in order to avoid hurting your back and damaging the threads on the studs that hold it on.
  8. Once you have removed the wheel, you can easily check tread depth. Use a gauge like the one shown. Tires normally have a wear bar that has shallower grooves than the rest of the tread. Moyer says you should always replace the casing by the time the wear bar gets close to the level of the tread. Only if the tire is replaced while there is still enough tread on it can you save the casing for retreading, or even operate safely.
  9. Assuming the tire has been repaired or replaced, and the wheel has been inspected and found to be in good condition, the next step is to remount it. Using a lever or tire-handling jig, position the wheel in front of the hub and then raise it until it can be slipped on over the studs. Try to keep the wheel from rubbing the studs as it slides on. Budd wheels are self-centering. Unimount wheels will have rounded flanges on the hubs that will center them.
  10. Install two or three nuts at the top and finger tighten. Then go around and install all the rest of the attaching nuts and tighten them hand tight.
    Note: The rest of the procedure involves torquing the nuts evenly all around the wheel, and doing it to just the right torque level. This is extremely important! When wheels come off or are damaged, it’s most often because somebody has not done this right.

  11. Check your owner’s manual and the labels on the cab door for wheel torque specifications. Moyer says torque varies with wheel type and truck brand. Dealers also often have charts and can give you the torque. If using an air gun, use a special tool called a torque stick. This device begins slipping and limits the torque output of the gun near the required level. Select a torque stick rated at or slightly below the torque specification for your wheel nuts. Install the torque stick so the inner end mounts on the drive of the air gun and the socket attaches to the outer end.
  12. Now begin torquing the nuts, in several (at least three) stages. In the first pass, stop the air gun after the nut tightens for just a second or so. Once the first nut is tightened a bit, skip across the wheel to the opposite nut and do the same with it. Next, go back to the nut next to the first one and torque that. Continue going back and forth across the wheel in this star pattern until all the nuts have been tightened just a bit evenly all around.
  13. Remove the jackstand and carefully lower the truck just until the wheel rests on the ground or floor, so the wheel won’t turn as you tighten the nuts farther.
  14. Then repeat the tightening procedure, but give the gun a couple of seconds to work at each nut. Once all the nuts have been tightened to this extent, repeat the entire procedure, going back and forth across the wheel, but this time keep the gun on until the torque stick stops turning on each nut (it may chatter as it does this to help you realize torque is correct).
  15. Finally, get a torque wrench of sufficient rating with a long handle. Set it to the torque specification for the wheel nuts. This wrench is set by releasing the locking handle, rotating the thumb-nut until the number in the window reflects the torque specification, and then locking the setting with the locking handle. If they give you a torque range, set the wrench to the middle of the range. The torque for this Mack truck with unimount wheels is 475 pounds-feet, which Moyer says is a very common torque specification.
  16. Then put the wrench on each nut and pull on the wrench until it clicks, indicating the torque is at the rating. Follow the same star pattern to make sure each nut is at the torque rating.
  17. It is extremely important that, after the truck runs 100 miles, repeat Step 16 to make sure torque is still correct. The wheel and nuts may work loose or adjust slightly after installation, and retorquing them after that distance will ensure they will seat properly and then stay stable for a long time. Torquing your wheel nuts occasionally even when wheels have remained mounted should be part of your periodic vehicle maintenance, as loose nuts can cause damage even when the wheel remains in place.

Wheel inspection
Wheels work harder than almost any other part of the truck, and they are subject to damage from road debris or when the driver runs over a curb. They need to be inspected and replaced when necessary to keep you safe and get you through roadside inspections.

They not only keep the truck in line but support it vertically. Unless the wheel fits snugly where it creates support, the parts will wear and cause continued deterioration, and you may even have a wheel fall off.

With unimount wheels, vertical support occurs where the inner diameter of the wheel rides against the flanges on the hub. Inspect the edges of the inner diameter of the wheel and make sure they are not worn to form an irregular edge with a wider-than-normal diameter. Inspect the flanges on the hub for wear. The wheel should fit over them all around without noticeable play. Also, inspect the flanges and the inner diameter of the wheel for flaking, which comes from overtorquing. Also look for rust, which can make the flanges swell and weaken them. The wheel or hub parts must be replaced if defective. Moyer says a rust streak running away from a wheel nut suggests it has gotten loose and may have been damaged.

With Budd type wheels, there are conical male and female surfaces on the rim and studs and nuts that have to fit one another snugly to support the chassis. You use a special gauge to see whether or not the surfaces have been worn out or rounded to the point where they’ll be loose. The female part goes on the outside with the wider part against the wheel, and the male portion is then put through the center of the female part from inside of the wheel. The male part must be recessed behind the outer edge of the female part, or the hole is rounded or worn excessively, meaning that the wheel should be replaced.

There is also a template for checking the stud and nut for Budd wheels. The tapered surfaces must match the tapered areas of the template, or these parts must be replaced.

Dayton wheels have a spoked hub that attaches to the rim. When torqued properly, there will normally be a slight gap between the corner of the spacer under the nut that faces the center of the wheel and the spoke. No gap indicates excessive wear.

Inspect wheels also for bent rims. Many people try to use a hammer to tap the rim back into the proper curved shape and may even try to heat the wheel first. “Don’t try it; it won’t go back,” says Moyer. He insists that the result is normally uneven mounting and, as a result, uneven treadwear and increasing vibration. Once a rim is bent it is also quite difficult to get a good air seal. Of course, the big reason rims get bent is running over curbs.

De-mounting and mounting the tire
The structure of the tire, including the bead, is easily damaged. Only the right tools and techniques must be used.

  1. Release as much of the air pressure as you can by depressing the valve stem.

  2. The second step is to get the wheel turned onto the right side for easy removal. There are two unequal bulges inside the rim, and you must get the narrower section upward. Moyer says this means laying the wheel down with the valve stem downward for most size rims. However, on most 19.5-inch rims, it should be upward.
  3. Make a soap and water solution, or get some tire and tube mounting compound, and then thoroughly douse the bead on both sides with it to lubricate the beads.
  4. Use a tire spoon and slide hammer to break the bead by wedging the spoon between the bead and rim at one point and then operating the slide hammer to force the two apart. Don’t use a pick-axe or other tool, as damage and sparks often result. Moyer says that, very often, once the bead is broken at one place it releases all around on both sides. Pry at additional locations, if necessary.
  5. Remove the valve stem by unscrewing it and then pulling it out.
  6. Next, use a spoon or special prying tool like that shown to gently pry the bead over the rim at one point. Then, carefully rotate the tool around the rim to pry the rest of the bead over the top.
  7. The final removal step is repeating Step 6 for the bead on the other side. Moyer says the special “gold” tool shown makes the job “10 times easier.” Relocate the tool to use it to force the lower bead over the upper rim. With regular tire spoons, you use two of them to work the tire off the rim by working them around it.
  8. Tire repair should be left to a pro. Make sure a punctured tire is not only plugged from the outside, but examined and sealed inside. The inner liner must be in good condition and must be sealed to keep moisture from rusting out the cords, a condition that can result in a sudden blowout.
  9. To remount, first coat all the surfaces with tire and tube mounting compound, used full strength. Then turn the tire to a horizontal position and work the lower bead over the upper rim of the wheel by hand. Then, use the spoon to pry a small section of the upper bead over the rim at one point. It has a small tab on one side you hook under the rim for more leverage. Finally, work the bead over the rim, a small section at a time, by prying gently with the tool.
  10. The last part of the job is seating the bead against the rim on both sides. Use only air pressure. Don’t try the time-honored, but potentially dangerous and destructive method of using ether because you may be injured and the tire can easily be damaged. The Cheetah tool consists of an air tank you charge with air from your air compressor. You then position the nozzle of the device between the rim and the bead, and open the valve to blast air into the tire and seat the bead. Other devices are available that connect directly to an air line without a tank.
  11. Inflate the tire, using a safety cage only! Portable safety cages are available and could be carried in a large, on-board toolbox. This is essential because if the cord structure of a tire has been damaged, it often comes apart with deadly explosive force. Install and tighten the tire stem valve with the special tool. Position the tire inside the cage and stand to one side, facing the tread of the tire. Inflate the tire gradually to its normal pressure, typically 105 psi.
  12. If a tire has been run flat, you need to safety test it. Slowly inflate it in a safety cage to 20 psi over its normal operating pressure. Moyer says you’ll often hear the cords tearing if they are damaged. If this happens, stop airing up the tire and stand aside. If the tire takes the pressure and holds it, undamaged, for 20 minutes, you can then deflate it to its normal pressure and use it.

Tire service is a precision job that requires the right tools and techniques. Practice what we have shown here and you’ll have a better safety record and longer tire and wheel life.

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