Grinding Tread

Toe-in: A condition that is present when the distance between the front edges of the front or rear wheels is less than the distance between the rear edges of the wheels.

Ford motor company performed a study which calculated that a 1/8 inch toe-in error is equivalent to dragging the tires crosswise 11 feet for each mile driven. As the tire rolls down the road, tread is grinding off. No other alignment angle is as important as toe, and no other angle is measured and adjusted to the 100th of a degree. The driver will force the vehicle to move straight down the road, and it is crucial the wheels roll in the same direction or they will grind crosswise across the pavement.

This reminds me of what happened the last time I was out of alignment.