Know How to Read Tire Tread Depth

Do you know what your tires are telling you about your car, road conditions or even your driving habits? If you know how to read tire tread depth and condition, a wealth of information is right at your fingertips.

How to Read Tire Tread Depth

Tire tread depth refers to the grooves between the main blocks on the contact surface of a tire. Most tires start with upwards of 10/32″ of tread depth, with some off-road tires topping 15/32″ depth. As you rack up the miles, the soft rubber compound, the very thing that gives you traction, wears away. Most states require a minimum tread depth of 2/32″ and some states require just 1/32″, but how do you measure it? Also, is 2/32″ really enough for a safe drive?

Do you know how to read tire tread depth with a tire tread depth gauge? Here is a five-step process to do it the right way:

1. Make sure the gauge is zeroed-out on a flat surface. You might be able to adjust the pin to get an actual reading of 0/32″.
2. In the air, push the measuring scale all the way in, so the measuring pin sticks out as far as possible.
3. Place the measuring pin in the main tread groove, and press down until the base of the gauge is resting firmly on the tread blocks on either side of the groove.
4. Carefully pull the tread depth gauge away from the tire, and read the measurement shown on the scale.
5. Repeat steps 1–4 for the other main tread grooves.

If you’re in a pinch, you can also get a rough estimate of tire tread depth by using a penny and a quarter. But this is no substitute for a calibrated tire tread depth gauge.

• The top of Lincoln’s head to the edge of a penny measures about 2/32″, the legal minimum in most states.
• The top of Washington’s head to the edge of a quarter measures about 4/32″.
• The steps of the Lincoln Memorial to the edge of a penny measures about 6/32″.

What Does It All Mean?

If you know how to read tire tread depth, this will help you determine when tire replacement is necessary, the condition of your suspension and steering system and if you need to change your habits.

• While most states require tire tread depth to be a minimum of 2/32″, most technicians and responsible people would recommend tire replacement around 4/32″, especially if lots of rain is a possibility in your area.
• If the outer tread grooves are deeper than the center groove, this could indicate that your tires are overinflated.
• If the center tread grooves are deeper than the outer grooves, this could indicate that your tires are under-inflated.
• If the inboard tread grooves are deeper or shallower than the outboard tread grooves, this could indicate a suspension alignment problem.

Keeping on top of your tire tread is actually much more than knowing when to replace them, it can also help you prevent other problems. Adding tire inspection to your monthly maintenance checklist might just keep you safer and your wallet heavier over the long haul.

Check out all the tools & equipment available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on tire tread depth and condition, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Foter