Wheel Alignment
Peculiar tire tread wear might not be caused by misalignment.
ED THOMAS
CONTRIBUTING EDITOR
"Wear and tear" is inevitable for any component on any commercial truck. What's unacceptable is unusual wear — the kind that costs abnormal amounts of money.
Tires tread on steer axles, for instance, are the first casualties of front-end misalignment, which develops as tie-rod ends, kingpins and other parts wear — or when the driver rams the front wheels into a curb. Some bashing is understandable, as is everyday normal wear. But it sure would be nice to know if something's amiss before it shows up as scrubbed tread.
Sensors mounted in the front end of future trucks might warn of those unwholesome developments, according to some industry experts. Just as they now monitor the health of various internal engine parts, sensors could watch alignment settings and warn owners when steering gear or axles go out of spec. That way they could be corrected before irregular tire wear even shows up.
In the meantime, such problems can be sidestepped by periodically checking alignment settings. Smart fleet people run trucks onto the alignment rack as part of a regular preventive maintenance visit, at whatever time or mileage interval makes sense for the operation. Like a high-tech sensor, the regular check and resetting, if necessary, can prevent irregular tread wear before it starts (and may be difficult to stop).
Everyone would like tires to wear down slowly and absolutely evenly, but mechanical and road conditions, not to mention what drivers do or don't do, conspire to put non-pretty patterns on the tread.
"Irregular wear" is really a catch-all term describing numerous ways that tread surfaces can degrade. Experienced and knowledgeable tire people can eyeball a tire and declare exactly what it is and what's causing it. Not many jacks of all trades can, unless they have training materials at hand.
One trove of tire knowledge is the Technology & Maintenance Council of ATA's Recommended Maintenance Practices Manual. In it is Recommended Practice 19A, which lists 26 wear conditions that can occur on heavy trucks, tractors and trailers.
Perhaps surprising is the fact that fewer than one-third of the 26 patterns are directly tied to front-end alignment or how the axles sit relative to the frame.
Sure, everyone knows that flat-spotting is the result of skidding, which could be induced by a sudden loss of air pressure and the spring brakes popping on or a driver's hard emergency braking (though anti-lock braking systems are supposed to have done away with that).
Most folks are also aware that some wear patterns are normal. "Step"-type wear along both shoulders, for example, is typical on steer-axle tires that wear slowly, as many of today's high-quality radial tires do.
But there are many others that tire and alignment specialists learn. Out-of-balance wheel/tire assemblies, improper tire inflation, worn shock absorbers, or worn wheel bearings are among many causes of irregular tread wear cited in the recommended practice. A quick reading of it brings one to the correct conclusion that the entire truck needs to be in good condition for "alignment" itself to be good. RP 219A lists possible causes with each type of tread wear; the wear pattern itself is illustrated with a photo and a drawing.
With this you can find your condition and cure it. RP 219A's authors are fleet managers and tire manufacturing engineers who together possess incalculable knowledge of the subject.
Members of TMC get the entire collection of RPs in the two-volume Recommended Maintenance Practices Manual. If you're not a member, check into buying the manuals by calling TMC at (703) 838-1754 or (800) 282-5463.
