Car care guide · Ford of Peoria · Peoria, IL
Tire Tread Depth: How Much Is Enough?
Tire tread depth is usually given in 32nds of an inch. With winter on the way in Central Illinois, here is the minimum depth NHTSA gives, how to check your tires with the wear bars or a penny, and the tread rules in Illinois law.
The short answer
NHTSA says tires are not safe and should be replaced when the tread is worn down to 2/32 of an inch, the same as 1/16 inch. Tires also have built-in treadwear indicators, and NHTSA describes a quick penny test. Illinois law treats a tire with less than 2/32 inch of tread (1/32 inch on a motorcycle or truckster) as unsafe to drive on a highway.
The minimum tread depth
NHTSA says tires are not safe and should be replaced when the tread is worn down to 2/32 of an inch. Its tire safety booklet puts the same limit as 1/16 of an inch; 2/32 and 1/16 are the same depth.
Tread is measured in 32nds of an inch, so a reading of 4/32 means four thirty-seconds of an inch of tread left above the bottom of the groove. That is the depth this guide means whenever it gives a fraction.
From NHTSA, Tire Safety Ratings and Awareness (nhtsa.gov) and the NHTSA tire safety booklet (DOT HS 809 361), read November 2, 2026.
How to check your tread depth
NHTSA recommends checking your tread at least once a month, when you check your tire pressure. Ways to check it:
Look for the wear bars
Tires have built-in treadwear indicators: raised sections that run in between the tire's tread. When the tread is worn down so it is level with those indicators, NHTSA says it is time to replace the tire.
Try the penny test
Place a penny in the tread with Lincoln's head upside down and facing you. If you can see the top of Lincoln's head, NHTSA says to replace your tires.
Check more than one spot
Tires do not always wear evenly. Illinois law measures tread in two or more adjacent grooves at three roughly evenly spaced places around the tire, including where the tread looks thinnest, and does not count a reading taken over a tread wear indicator.
Look for other damage
NHTSA's booklet suggests inspecting tires for uneven wear patterns on the tread, cracks, foreign objects or other signs of wear or trauma.
From NHTSA, Tire Safety Ratings and Awareness, the NHTSA tire safety booklet (DOT HS 809 361) and 625 ILCS 5/12-405, Illinois Vehicle Code (tires), read November 2, 2026.
What Illinois law says about tread depth
| Rule | Tread depth |
|---|---|
| Tire unsafe to drive on an Illinois highway | Less than 2/32 inch (1/32 inch on a motorcycle or truckster) |
| Front tire on a vehicle subject to Chapter 18B of the Vehicle Code | Less than 4/32 inch at any one location |
| Tire, or a vehicle with a tire, sold or leased for highway use | Must have at least 3/32 inch (2/32 inch on a motorcycle or truckster) |
From 625 ILCS 5/12-405, Illinois Vehicle Code (tires), read November 2, 2026. For the unsafe-tire rule, the statute measures tread depth in two or more adjacent grooves at three roughly evenly spaced locations; none of the limits count a measurement over a tie bar, tread wear indicator, hump or fillet. This is general information, not legal advice.
Why tread depth matters
NHTSA explains that tire tread provides the gripping action and traction that keep your car or truck from slipping and sliding, especially when the road is icy or wet. That is why worn tread is a safety issue, not just a cosmetic one.
How fast tread wears depends partly on the tire. NHTSA says that the higher a tire's treadwear grade, the longer the tread should take to wear down; for example, a tire graded 200 should wear twice as long as the control tire. Even with tread left, NHTSA notes that some vehicle and tire manufacturers recommend replacing tires that are six to 10 years old, regardless of treadwear.
From NHTSA, Tire Safety Ratings and Awareness, read November 2, 2026.
Service at Ford of Peoria
The Works® at Ford of Peoria includes a synthetic blend oil change, tire rotation and pressure check, brake inspection, Multi-Point Inspection, fluid top-off, battery test, and a filter, belts and hoses check. For tire details, see our tire service page.
Schedule service online and see our service specials first. Ford of Peoria is at 2211 W. Pioneer Pkwy. in Peoria. Get directions.
Ford of Peoria service hours
| Days | Hours |
|---|---|
| Mon-Fri | 7 a.m.-5:30 p.m. |
| Sat | 8 a.m.-noon |
| Sun | closed |
From Ford of Peoria's website, November 2, 2026. Holiday hours can differ.
Tire tread depth FAQ
What is the minimum safe tire tread depth?
NHTSA says tires are not safe and should be replaced when the tread is worn down to 2/32 of an inch (1/16 inch).
How do I do the penny test?
Place a penny in the tread with Lincoln's head upside down and facing you. If you can see the top of Lincoln's head, NHTSA says to replace your tires.
What are tread wear indicators?
Raised sections built into the tire that run in between the tread. When the tread is worn down level with them, NHTSA says it is time to replace the tire.
What is the legal tread depth in Illinois?
Under 625 ILCS 5/12-405, a tire with less than 2/32 inch of tread (1/32 inch on a motorcycle or truckster) is unsafe to drive on an Illinois highway, and a tire or vehicle sold or leased for highway use must have at least 3/32 inch (2/32 inch for motorcycle and truckster tires).
How often should I check my tire tread?
NHTSA recommends checking your tread at least once a month, when you check your tire pressure.
Is 4/32 tread depth OK?
4/32 inch is above the 2/32-inch point at which NHTSA says to replace tires, but the tread is getting closer to that limit. Keep checking monthly, and remember that some vehicle and tire makers also recommend replacing tires at six to 10 years old regardless of treadwear.
What does The Works at Ford of Peoria include?
The Works® at Ford of Peoria includes a synthetic blend oil change, tire rotation and pressure check, brake inspection, Multi-Point Inspection, fluid top-off, battery test, and a filter, belts and hoses check.
Tread looking thin?
Book The Works, which includes a tire rotation and pressure check, brake inspection and Multi-Point Inspection, at Ford of Peoria.
Sources
Tread depth limits, checks and tire facts are from NHTSA's tire safety page and booklet, and the Illinois rules are from 625 ILCS 5/12-405, all read November 2, 2026. This page is a summary, not legal advice. Service details, address and hours are from Ford of Peoria's own website, checked the same day. Photo is illustrative.
- NHTSA, Tire Safety Ratings and Awareness, NHTSA, read November 2, 2026
- NHTSA tire safety booklet (DOT HS 809 361), NHTSA, read November 2, 2026
- 625 ILCS 5/12-405, Illinois Vehicle Code (tires), Illinois General Assembly, read November 2, 2026
- Tire service, Ford of Peoria, November 2, 2026
- General service: The Works, Ford of Peoria, November 2, 2026
- Address and service hours (structured data), Ford of Peoria, November 2, 2026