A commercial tire dealer's job is getting more complex and demanding all the time as fleets exert their desires to remove themselves from the tire business and outsource tire maintenance, problems and concerns to their suppliers.
You've got to hone your skills to a fine edge to protect your company's interests as well as provide service your fleet accounts expect.
Irregular wear—caused by vehicle misalignment—is perhaps the most common tire problem that major fleets face. The key is determining the cause of this wear and correcting it to make your customer happy and to prevent the unnecessary issuance of "policy adjustments" when the fault lies squarely with the truck tire user.
Full shoulder wear, feather wear and one-sided wear are steer tire wear conditions caused by some form of misalignment.
Full shoulder wear appears as excessive wear across an entire shoulder rib to a major tread groove and usually is evident on one side of the tire only. It occurs as a result of side scrubbing and is generally caused by either an improper toe condition or drive-axle misalignment.
If a toe-in condition is causing this wear, the outside shoulders of both steer tires will be worn, whereas if the axle is toed-out, the inside shoulders of both steers will be worn.
A misaligned drive axle will push the vehicle in the direction the axle is facing. This forces the driver to turn the steering axle in the opposite direction to keep the vehicle going straight. As a result, the inside shoulder of one tire and the outside shoulder of the other steer tire are scrubbed and wear faster than the rest of the tread.
Poorly maintained suspension components such as torque rods, springs and spring bushings can produce the same type of wear. If this condition occurs on perhaps only one tire, check the seating of the bead. An improperly seated bead will create this condition and can as easily be the cause on both steer tires.
Feather wear is a condition in which the tread ribs are worn high to low on each rib across the tread face. This is the result of undue side force scrubbing that is caused by excessive toe. It also can be caused by severe drive-axle misalignment, worn, missing or damaged suspension components, bent tie rods or other symptoms of chassis misalignment.
If you find that this wear is identical on both steer tires, then drive-axle or other chassis alignment should be checked. When the steer tires are worn in opposite directions, then the setting on the front axle should be corrected. As with full shoulder wear, if the feather is toward the center of the vehicle, then a toe-in condition exists. If it is toward the outside of the tires, a toe-out condition is the cause of the wear.
One-sided wear appears as disproportionate wear on one side of the tire and extends from the shoulder towards the center of the tread. The most common causes of this condition are improper camber and drive-axle misalignment. However, it can also be caused by worn king pins, loose front wheel bearings and excessive axle loads.
Camber is the inward or outward tilt of the wheels when viewed from the front of the vehicle. It is the angle that moves the centerline of the tire from vertical and is built into the axle during the manufacturing process. It is not adjustable after the axle is installed on the vehicle.
Tires perform best when they run perpendicular to the road surface under typical operating conditions. Camber can be corrected by replacing worn parts such as kingpins and spindles, but axles or spindles should never be "bent" to correct camber.
While full shoulder wear, feather wear and one-sided wear are pretty clear-cut conditions, steer tire irregular wear can be complicated by having two or three conditions working on the steer tires at the same time.
For example, if you find a pair of steer tires that have full shoulder wear on three shoulders, it is possible that you have a toe-in condition that is wearing the outside shoulders of both tires in addition to drive-axle misalignment that is wearing the outside shoulder of one tire and the inside shoulder of the other tire. The key is to look at the wear and figure out from where the forces are coming.
Besides steer tires, drive and trailer tires also can suffer from misalignment induced irregular wear. Similar forces that scrub the tread off steer tires work the same on tires located behind the driver. Drive axles can experience full shoulder wear if the axle is not perpendicular to the frame.
Trailer tires also can exhibit rapid shoulder wear on one shoulder, which can progress to a diagonal wipeout. Excessive toe and excessive camber usually cause this irregular wear.
This mechanical condition can be created by a misaligned or bent axle and can also be caused by loose or worn wheel bearings. Trailer tires also commonly exhibit one-sided wear as a result of excessive toe, excessive axle camber, non-parallel axles and improper bead seating.
So what do you do if you suspect you have a vehicle with an alignment condition. Well, if you have a portable alignment measuring kit or a string, plumb bob and a 50-foot tape measure you could check to see if the axles are parallel. Most fleets have the simple equipment needed to check toe and can do this fairly quickly.
Also, you can just walk around and under the vehicle and look for areas of movement in the suspension indicated by things such as rust around the U-bolts that would indicate the axle has shifted, as well as cracks in the springs and spring hangers and wear in the bushings. Often these things are really obvious, but in some fleets no one ever looks at them.
If you are not comfortable checking basic alignment, then recommend to the fleet that the vehicle alignment be checked. If the tractor is usually paired with the same trailer, also recommend that the trailer alignment be checked since it can be the cause of irregular wear on the forward axles.