HOW TO MEASURE TIRE TREAD DEPTH
Wear on Both Edges: Underinflation
Underinflation increases the treadwear on a tire's outside edges and generates excessive heat, reducing the tire's toughness. Soft tires also increase rolling resistance, reducing fuel economy.
Wear in Center: Overinflation
Overinflation increases wear on the center tread.
Cups or Dips in the Tread: Worn Parts
Cupping or dipping is most common on front tires, but rear tires can cup as well.
Sawtooth Edges: Misalignment
Misalignment causes erratic scrubbing against the road giving the tire's edges a sawtooth-like appearance.