SAFE TREAD ALLIANCE

4/32

Tire

Advancing Modern Tire Safety Standards in the United States

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Safer Tires Save Lives.

Safe Tread Alliance

Raising the Standard for Tire Safety in America

The Safe Tread Alliance is leading a national effort to modernize minimum tire tread depth laws through the 4/32 Initiative,  a science-backed proposal designed to reduce wet-weather crashes, improve stopping performance, and close a dangerous gap in U.S. safety regulations.

A person with a beard uses a caliper to measure the tread depth of a car tire.
A yellow circular logo featuring the bold black text
A yellow circular logo featuring the bold black text

The Hidden Risk on America’s Roads

Tires are the only part of a vehicle that make contact with the road. Yet in most states, the legal minimum tread depth remains 2/32 of an inch, a standard established decades ago — long before modern performance testing methods were widely adopted.

By the time a tire reaches 2/32:

Millions of drivers unknowingly operate vehicles at tread depths that are technically legal but no longer optimally safe.

The 4/32 Safety Threshold:

Where Stopping Power Drops, Traction Fails, and Crash Risk Rises

Real-world data shows that below 4/32, tires rapidly lose performance in wet conditions — increasing stopping distance, reducing control, and raising the likelihood of crashes.

0 %
Longer Stopping Distance on Worn Tires
0 %
Less Wet Traction Below 4/32
0 +
Crashes Linked to Tire Issues Each Year

The 4/32 Initiative — Closing the Safety Gap

The 4/32 Initiative calls for updating the minimum legal tread depth to 4/32 of an inch, a threshold supported by performance data showing improved:

This initiative does not encourage premature tire replacement. It promotes replacing tires before performance degradation reaches dangerous levels.

Built on Experience. Backed by Expertise.

Safe Tread Alliance was formed following a preventable tragedy caused by excessively worn tires. That lived experience became the catalyst for a coalition of:

Our mission is not symbolic. It is measurable: reduce preventable crashes by modernizing outdated standards.

FAQ

Frequently Asked Questions About Tire Safety

  • What is the safest minimum tire tread depth?

    For wet-weather safety, 4/32 of an inch is widely recommended because tires retain stronger traction and water evacuation than they do at the 2/32 legal minimum.

  • Is 2/32 tire tread depth safe?

    2/32 is the legal minimum in most states, but wet-weather traction and hydroplaning resistance are reduced compared to higher tread depths like 4/32.

  • How does tread depth affect hydroplaning?

    As tread depth decreases, the tire’s grooves channel less water, increasing the likelihood of hydroplaning and reducing vehicle control in wet conditions.

  • Is the penny test a reliable way to know if my tires are safe?

    The penny test can indicate when you’re near the legal minimum, but it does not measure optimal wet-weather safety. A tread depth gauge provides a more accurate reading.

  • How often should I inspect my tires?

    Check tires monthly for tread depth, pressure, and visible damage, and get a professional inspection at least once a year or before long trips and rainy seasons.

The 4/32 Initiative is dedicated to protecting families on the road by ensuring every tire meets a safety standard that reflects real performance, not outdated minimums.

Safer Tires Save Lives.

How You Can Help

Raising tire safety standards requires action from lawmakers, industry leaders, and everyday drivers.

A customer and a mechanic in a tire shop examine a car tire together.

Our Trusted Partners

The Safe Tread Alliance is actively building partnerships with leading organizations committed to advancing road safety: