Glossary

Tread depth gauge

Last reviewed: 2026-05-20

A tool for measuring tread depth in major tread grooves. Probe-type gauges insert directly into grooves and give a direct reading in 32nds of an inch or millimeters. Unlike the coin test (which is not calibrated and not reliable for commercial vehicles), a proper gauge gives a measurement that can be compared to federal thresholds and fleet pull points.

Use a gauge, not a coin or visual estimate, when tread depth is close to a removal decision. A coin test that suggests adequate depth may still be above or below the 4/32 inch steer minimum.

Real-World Use

A fleet requiring gauge-based measurements at each inspection identifies a steer tire at 4/32 inch — below fleet policy threshold — that would have passed a visual check.

What to Pair It With

Read this term with the full tire sidewall, vehicle rating information, manufacturer documentation, and the actual condition of the tire.

This site is for general information only. It does not replace professional tire service, DOT compliance advice, tire manufacturer instructions, vehicle manufacturer recommendations, or fleet policy.