Keeping Your Eye on the Ball Will Keep Fleet Customers Rolling Trouble-Free
Since fleets are beginning to recognize the importance of tire inflation pressure maintenance, the number of tractors and trailers inspected on a daily basis is probably as high as it’s ever been.
Unfortunately, too many technicians just check the tread depth and the air pressure and move on to the next tire. It only takes a few seconds to inspect the entire assembly, so all of the vital components should receive regular maintenance and service, if necessary.
In an effort to help commercial tire service technicians remember the main steps in a complete fleet tire and wheel check, just think of BATS: Bolt holes; Air pressure; Tread depth and condition; and Studs, stem and sidewalls.
Bolt Holes
A critical point on every wheel is the bolt hole. For stud-piloted wheels, the chamfered seats in the bolt holes center the wheels on the hub and clamp them to the vehicle. Since the stud-piloted system depends on friction between the fastener and the ball seats to create bolt tension, the metal-to-metal twisting contact causes the harder inner/outer cap nut to gradually wear away the softer chamfered bolt hole.
When inspecting stud-piloted wheels, technicians should carefully check the area where the cap nut meets the wheel for cracks or excessive corrosion. Any sign of damage requires the removal of the wheels so all of the components can be thoroughly checked for any out-of-service conditions.
On hub-piloted wheels, however, bolt holes do little more than provide a space for the stud to pass through, because the pilot pads center the wheel and the clamping force provided by the two-piece flange nut doesn’t depend entirely on the condition of the bolt hole.
While the bolt hole in the hub-piloted wheel system has a single purpose, an inspection of the area surrounding it can often determine if any potential hazards exist.
When the flange nut is overtorqued and not lubricated, it leaves a distinct worn circle around the bolt hole. Once the flange makes contact with the wheel, that circle shouldn’t move.
If it appears that a fresh circle has "slipped," that may indicate a loose wheel. Evidence of possible movement around the flange nut and the bolt hole area requires further attention. If there’s any question, the wheels should be removed and carefully inspected before they are returned to service.
The most obvious thing to look for is any sign that the wheels have moved or slipped while in service. An obvious change in color around the bolt holes may indicate that they were recently changed or moved.
Rust streaks are especially good indicators of loose outer cap nuts. But not all streaks on the wheel surface are the result of corrosion. It’s almost impossible to decide which streaks could be a problem and which pose no risk, so technicians should always remove them and make a note if the wheels are left in service. If the streaks are found on the same wheel position at a later inspection, the technician will know they need further investigation.
Small cracks extending from bolt holes generally require a close inspection and cleaning of the wheel surface, so technicians should be careful to check all eight or 10 bolt hole areas.
Air Pressure
Checking the inflation pressure can only be accomplished with a calibrated air gauge applied to the end of the valve stem. While the most experienced and educated ear or boot can determine if one tire has substantially less air pressure than the surrounding tires, it will never be an accurate measure in the eyes of an OSHA inspector or an attorney.
After the inflation pressure has been determined, the technician must decide which action must be taken:
®′ If the tire is less than 20% underinflated, it can be inflated to the recommended fleet tire inflation pressure and left in service.
®′ If the tire is more than 20% underinflated, it must be completely deflated and removed from service so that it can be demounted and thoroughly inspected on the inside for any potential signs of a zipper rupture.
®′ If the tire is overinflated and cold, it should be deflated to the recommended fleet tire inflation pressure.
®′ If the tire is overinflated and hot, the inflation pressure should not be adjusted in any way. Once the assembly cools, the correct pressure can be determined.
Notice that all of the actions are based on the "recommended fleet tire inflation pressure" and not on the maximum tire inflation pressure listed on the sidewall. Some fleets inflate their tires to carry a specific load, and overinflating a tire can be just as harmful as ignoring an underinflated one.
If the recommended fleet pressure is 90 psi (but the sidewall has a maximum load at 100 psi), the 20% reduction must be calculated using 90 psi, so a tire with less than 72 psi should be deflated and removed from service for further inspection.
Tread Depth and Condition
Since federal laws require a certain amount of tread depth, and failure to comply results in fines, fleets expect technicians to check the remaining non-skid tread depth in several places. It should always be measured at the lowest points but never determined at the wear indicators between the lugs or grooves. In fact, if the wear indicators are level with the surrounding tread, the tire has less than 2/32-inch tread depth at that point and should be removed from service.
When a tire is properly balanced and inflated and wheels are properly aligned, the wear pattern will probably be smooth and even across the face of the tire.
An irregular treadwear pattern is usually an indication of a problem that needs correction. Remember, irregular treadwear will very rarely correct itself during service, and underinflation is the most common cause of irregular treadwear.
Once again, a quick scan for cuts or embedded foreign objects can identify a potential hazard, so the technician should correct it before an accident occurs.
Studs, Stems and Sidewalls
Regardless of the wheel or rim system, the studs and nuts must generate enough clamping force and bolt tension to hold the assemblies to the vehicle. The condition of the components has a direct effect on the amount of force created. Excessively corroded or worn fasteners can result in loose wheels or rims. If any studs are missing, the vehicle should be taken out of service until this is repaired.
While stud replacement is not part of a fleet tire and wheel inspection, it’s important to review the correct procedures. If only one stud is broken, the broken stud must be replaced in addition to the studs on either side (for a total of 3 studs). If more than one stud is broken, they must all be replaced. On stud-piloted wheels, the broken stud rule also applies to inner cap nuts.
It’s impossible to discuss broken studs on stud-piloted wheel systems without mentioning "dummying." An experienced technician should be able to look at a bolt circle and determine if any studs are missing just by comparing the number of threads extending beyond the outer cap nut. Like everything else, dummying a broken stud is never a problem until someone gets hurt.
Likewise, a fleet tire and wheel inspection that does not detect a dummy inner and outer cap nut creates a certain degree of liability if the problem is not recorded and corrected.
A tubeless tire can’t hold air if the seal at the valve stem hole is bad, so the area immediately surrounding it must be inspected. A properly torqued valve stem should move very little when force is applied. Loose stems should be tightened with a torque wrench.
If the stem moves too much or if the grommet is damaged, the assembly must be removed and the valve stem replaced.
In inspecting sidewalls, any open cuts exposing body cords or steel must be repaired before the tire can be returned to service.
In some instances, a "pencil" bulge does not pose any risk, while in others it is the sign of a significant weak spot on the tire. If any sidewall bulge exceeds 3/8-inch or appears to be more than a few cords wide, the tire should be removed from service. It’s impossible to thoroughly inspect the inner sidewalls for obvious reasons, but the outside sidewall generally receives the majority of the abuse, so a quick inspection is necessary.
Technicians must recognize their responsibility to keep the highways safe from wheel-offs and other avoidable accidents. By definition, preventive maintenance means potential hazards are identified and corrected before they result in a breakdown or accident.
Like most other out-of-service conditions, they are rarely found if the technician never looks. Thumping and bumping through a tire inspection is definitely easier and takes less time. But cracked bolt holes, underinflated tires, illegal tread depths, corroded studs, loose valve stems and damaged sidewalls are rarely identified when technicians don’t bother to look for them.
This article was reprinted from the Tire Industry Association’s Commercial Tire Service Today publication.
