Before a long trip, you do the penny test on your two front tires, with Lincoln's head first in the deepest groove. On the left tire, you can see all of Lincoln's head. On the right tire, the tread covers the top of his head. What should you do?

Correct answer: Replace the left tire, because it fails the test; the right tire passes.

Why

The manual gives 2/32 inch as the minimum tread depth, and the penny test is a quick way to check the tread at home. Worn tires lose grip on wet and snowy roads, so replace a worn tire before you drive on it. Check all four tires, and keep each one at the right air pressure, because over-inflated and under-inflated tires also reduce traction.

Verified against Vermont Driver's Manual · Vehicle condition · p. 61