How to Gauge Tire Depth

Properly gauging tire tread depth is not just a legal issue, but a safety issue as well. When your tires have worn down past a certain point, you may have more difficulties with hydroplaning in wet weather. You may also face more dangerous driving conditions in snowy or icy conditions. Additionally, police can issue you citations if your tire treads do not meet the legal criteria of your jurisdiction. Fortunately, you can be sure of your tire tread depth using either a tire gauge or a simple US coin.

Things You'll Need

• Tire tread depth gauge (optional)
• Penny (optional)
• Quarter (optional)
• Pen or pencil
• Paper
• Calculator (optional)

Instructions

Using a Tire Tread Depth Gauge

1. Check whether your tire depth gauge measures in millimeters or 32nds of an inch. Different gauges measure in one or both ways.

2. Calibrate your gauge on a hard, even surface by pushing the gauge into the base as far as it will go with both the gauge and the base touching the flat surface. Next, push the base up on the gauge until the gauge has gone down as far as you can push it inside the base.

3. Choose one of the grooves that goes all the way around your tire. Put the probe directly in the center of that groove and push it down, balancing the base across both sides of the groove. Push the probe as far as it will go into the tread, but do not push too hard or you will damage your tire.

4. Pull the gauge away from the tire by the base; do not touch the probe. Write down the number you see on the probe.

5. Repeat steps one through four in several places around the tire, about a foot apart. Always use the grooves that go around the tire, not the ones radiating out toward the sidewalls.

6. Add all readings together and average them to get an accurate picture of your tire tread depth. Use a calculator if you like.

Using a Coin

1. Stick a penny in a groove going around the circumference of the tire so that Lincoln's head is facing downward. If you cannot see the top of his head, you have at least 2/32 of an inch of tread remaining. This is important, as in many states that is the lowest level your tread can legally be. Repeat process in several places around the outside of the tire to check that it is wearing evenly.

2. Repeat the process with a quarter. If you cannot see the top of Washington's head, you have at least 4/32 of an inch of tread left.

3. Repeat the process with a penny facing backwards, and the Lincoln Memorial upside down. If you cannot see the top of the Memorial, you have at least 6/32 of an inch remaining.

Tips & Warnings

• Checking your tire tread depth in several places around each of your tires can alert you to uneven wear patterns that could shorten the lives of your tires.

References

• Measuring Tire Tread Depth with a Tire Gauge
• Measuring Tire Tread Depth with a Coin