Use the penny test: insert a penny into the tread groove with Lincoln’s head upside down and facing you
Check if the top of Lincoln’s head is covered by tread
Use a tread depth gauge for an exact measurement
Measure tread depth in multiple spots across each tire
Check the center, inner edge, and outer edge of the tread
Look for wear bars built into the tire tread
Replace the tire if the tread is level with the wear bars
Inspect for uneven wear patterns
Compare tread depth on all four tires
Test both front and rear tires separately
Check tread depth when tires are cold and on level ground