Full Shoulder Wear
Excessive wear extending across entire shoulder rib to a major tread groove, usually on one side of tire only.
Result of side scrubbing and generally is caused by either improper toe condition or drive axle misalignment.
In case of toe in, the outside shoulders of both steer tires will be worn, while in the case of toe out, the inside shoulders of both steers will be worn. Drive axle misalignment wears the inside shoulder of one tire and the outside shoulder of the other steer tire. Poorly maintained suspension components (e.g. torque rods, springs, and spring bushings) can produce the same results.
If wear is severe, tires can be rotated to another position or reversed on the wheel.
Diagnose misalignment, check suspension components, and correct as required.