Tire tread depth directly affects your ability to stop in wet weather. As the tread wears down, the grooves that channel water away from the contact patch get shallower — the tire hydroplanes more easily and wet stopping distance increases. Knowing how to check your tread depth takes 30 seconds and could save your life.
The penny test
Insert a penny into the tread groove with Lincoln head facing down. If you can see the top of Lincoln head — the area above his head — the tread depth is below 2/32 inch. At 2/32 inch, the tire has reached the minimum legal tread depth in most U.S. states and should be replaced immediately.
The penny test is a go/no-go check: if Lincoln head is fully visible, replace the tire. If Lincoln head is partially hidden by the tread, the tire is legally above minimum — but that does not mean it is safe in wet weather.
The quarter test
Insert a quarter into the tread groove with Washington head facing down. If you can see the top of Washington head, tread depth is below 4/32 inch. At 4/32 inch, wet-weather braking performance begins to degrade noticeably. Most tire safety experts recommend replacing tires at or before 4/32 inch — not waiting until the legal minimum of 2/32 inch.
Think of the quarter test as the practical threshold. Tires at 4/32 inch have measurably longer wet stopping distances than new tires. A tire passing the penny test but failing the quarter test is legal but increasingly unsafe in rain.
Using a tread depth gauge
A tread depth gauge is a $5 to $15 tool available at any auto parts store. Insert the probe into the tread groove and push the base flat against the tire surface — the gauge reads the depth in 32nds of an inch.
New tires typically start at 10/32 to 11/32 inch of tread depth. When you reach 4/32 inch, start shopping. When you reach 2/32 inch, stop driving on the tire.
Check tread depth at multiple points across the tire width — inner edge, center, outer edge. Uneven wear (one edge significantly more worn than the other) indicates alignment or inflation problems that should be addressed even if the minimum depth is still met.
Frequently asked
How deep is new tire tread?
Most new passenger tires have 10/32 to 11/32 inch of tread depth. Some winter tires start at 12/32 inch. High-performance summer tires may start as low as 8/32 inch.
When should I replace my tires?
Replace at 4/32 inch for safety in wet weather. 2/32 inch is the legal minimum in most states — by that point stopping distance in rain is significantly longer than new tires. If the quarter test shows Lincoln head, start shopping. If the penny test shows it, replace immediately.
Does uneven tread wear mean I need alignment?
Uneven tread wear — where one edge of the tire is more worn than the other — is a common sign of misalignment. It can also indicate over- or under-inflation. Get a wheel alignment check and correct tire pressure before the wear destroys the new tires.
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Last updated 2026-06-27. General guidance only — confirm specifics with a local shop for your exact vehicle.