Park the vehicle on a level surface and set the parking brake
Turn the steering wheel if needed to access the tread area
Use a tread depth gauge for the most accurate measurement
Insert the gauge probe into the deepest groove of the tire tread
Press the gauge base flat against the tread blocks
Read the measurement in 32nds of an inch or millimeters
Check multiple spots across the tire width
Check several points around the tire circumference
Compare all readings to find uneven wear
Use a penny or tread wear indicator bars if a gauge is not available
Insert a penny into the tread with Lincoln’s head facing down
Replace the tire if tread depth is below legal or recommended limits