Tires that have been operated with ___ inflation pressure will have their tread worn away on the shoulders more than in the center.

• A. High
• B. Normal
• C. Overinflated
• D. Low

Answer: (D)

The main idea is how inflation pressure changes how a tire wears. When inflation is too low, the tire flexes more as it rolls, which enlarges the contact patch at the edges. The outer portions of the tread (the shoulders) carry more load and scrub harder against the road, so they wear down faster than the center. If inflation were higher than needed, the center would wear more because the crown bears more of the load. Normal inflation tends to produce even wear across the tread. So, wear concentrated on the shoulders with the center eroding more slowly points to underinflation.