Glossary

Tread depth

Last reviewed: 2026-05-20

The depth of usable tread measured in the major tread grooves with a proper gauge. For commercial motor vehicles under 49 CFR 393.75, the federal minimum is 4/32 inch on front steer axle tires and 2/32 inch on other positions. The lowest valid groove reading controls the removal decision, not the average of several better-looking readings.

Measure several spots around the tire and across the tread because irregular wear can hide the lowest point. The legal minimum is a floor, not a target for removal. Many fleets set higher pull points to preserve casing value, reduce roadside exposure, and keep steer tires well above minimum before dispatch.

Real-World Use

A tire can look acceptable from the outside shoulder while the inside rib is already near the steer-axle removal depth of 4/32 inch. A technician records each rib separately and removes the tire based on the lowest reading rather than the visual impression from one side.

Reference Sources

Sources used for context and verification of regulatory thresholds, inspection criteria, and compliance references on this page.

Gov 49 CFR 393.75 - Tires (Electronic Code of Federal Regulations, reviewed 2026-05-20)
Ind CVSA North American Standard Out-of-Service Criteria overview (Commercial Vehicle Safety Alliance, reviewed 2026-05-20)

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.