Minimum Tire Tread Depth: Legal vs Safe (2/32", 4/32", and mm)

2026-01-07•By TireCheck Team

Minimum Tire Tread Depth: Legal vs Safe (2/32", 4/32", and mm)

Drivers often ask: “What is the minimum tread depth to replace tires?” The honest answer depends on whether you mean legal or safe for your conditions.

This article explains the commonly referenced thresholds, how to measure accurately, and how to decide based on rain, snow, and driving speed.

The Common Thresholds (Inches and Millimeters)

•2/32 inch (≈ 1.6 mm): widely treated as the minimum legal tread depth for passenger tires in many U.S. contexts.

•4/32 inch (≈ 3.2 mm): a practical threshold for improved wet performance; many drivers replace “at or near” this level.

•6/32 inch (≈ 4.8 mm): often recommended as a planning threshold for frequent snow driving (tire type matters).

Why “Legal” Can Still Be Risky

At 2/32", grooves are shallow. In real-world rain, especially at highway speeds, water evacuation is reduced and hydroplaning risk rises. Wet braking distances can increase sharply near the end of tread life, even if the tire isn’t “bald.”

If you want a quick screening:

•Tire Tread Penny Test: How to Do It Correctly

•Check Tire Tread With a Quarter: Why 4/32" Matters

For precision, use a gauge:

•How to Measure Tire Tread Depth (Gauge Method)