Tread depth is one of the more important safety checks that you can do on your vehicle. When accelerating, braking, or steering, you only have a small patch of rubber between your hundreds of pounds of motor vehicle and the hard surface of the road.
If that small rubber patch isn’t in good condition, the risks you’re subjecting yourself and your passengers to are pushed higher than acceptable.
Here we’ll talk about that patch of rubber and how to make sure it’s legal.
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Quick Questions Before Starting
Measuring the tread depth on your tires is a simple procedure that you can do on your own. It’s not a skilled task. It should be scheduled regularly, depending on how many miles you drive in a month.
How Difficult Is This to Do?
This is a straightforward task that needs no experience to undertake.
How Long Does it Take?
This should take you no longer than 30 minutes to check all four wheels and the spare.
How Much Do Materials Cost?
If you’re using a penny or a quarter to do a rough check, there’s no cost. If you want to measure the tread depth accurately, a tread depth gauge will have to be purchased. A good manual gauge will cost in the region of $5 to $12 and a digital gauge between $13 and $15.
Things You Can Use to Check Tire Tread
There are four ways that you can check the tread remaining on your tires. Only one of these methods requires you to buy a tire tread depth gauge. The others are household items or built into the tire.
Tread Wear Indicator
On all tires, there’s a treadwear indicator built into the tread. If you look at the tread, you’ll see bands of rubber placed across the widest grooves of the tread at regular intervals around the tire’s circumference.
If you look at the tire’s side, you’ll see the letters TWI meaning Tread Wear Indicator. If the tread of the tire is level with the indicators, it means that your tires must be replaced.
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Penny Test
A simple test that will give you a good idea of whether your tires are worn is to use a penny. Hold the penny with Lincoln’s head facing toward you and with the head pointing down toward the surface of the tire. Drop the penny into the grooves of the tread.
If you can see all of Lincoln’s head, it means your tire must be replaced as the depth is less than ²/₃₂ “. If any of his head is obscured, your tire is good to go.
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Quarter Test
Another simple test with a coin is to use a quarter. Again, hold the quarter with Lincoln’s head facing you and with the head pointing at the surface of the tire. Drop the quarter into the grooves of the tread.
If the tread touches Lincoln’s head, then you have approximately ⁴/₃₂” of tread left. This means the tire is still legal, but it’s getting very close to its legal limit, and you should be making plans to replace it.
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Tire Tread Gauge
The most accurate means of measuring tread depth is to use a tread depth gauge. These gauges can be purchased from any good auto parts store or online. All of them work similarly. At one end will be a pointer that you place in the groove of the tread. You then push the barrel of the gauge down until it touches the raised portion of the tread.
Digital gauges have a screen where you can read the tread depth, but manual gauges need you to read the scale at the top of the gauge. A manual gauge should cost you between $5 and $12 and a digital gauge between $13 and $15.
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How to Measure Tire Tread Depth: 4 Methods
It’s straightforward to measure the depth of tread left on your tires. This is a task that anyone can undertake, and you require no special training.
The first thing that you should do is look at the tread across the tire. If there’s any place where the tread is worn down more than anywhere else, then you must measure the most worn part of the tire.
Uneven tread depth indicates a problem with your wheels’ alignment and needs to be repaired as soon as possible. Remember to measure all the tires on the vehicle and don’t forget the spare.
If you drive on winter tires, certain SUV tires, high-performance tires, or truck tires, please refer to the manufacturer’s specifications for the tread depth. These tests don’t apply to these types of tires.
1. Using the Tread Wear Indicators on the Tire
a. Sit comfortably by the tire so you can see the sidewall and the tread clearly.
b. Make sure the sidewall is clean so you can read the text on it.
c. Look for the letters TWI on the sidewall. These stand for Tire Wear Indicator.
d. From these letters, run your finger up to the tread of the tire.
e. Now carefully look at the tread. In the grooves between the tread blocks, you should see bars of rubber running across the grooves.
f. These bars are the minimum legal depth of tread for the tire.
g. If these bars are level with your tread, then the tire must be replaced.
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2. Penny Test
a. Sit comfortably next to the tire so that you can clearly see the tread.
b. Hold the penny with Lincoln’s head facing toward you and with the head pointing down toward the surface of the tire.
c. Drop the penny into the grooves of the tread until it can go no further.
d. If you can see all of Lincoln’s head, it means your tire must be replaced as the depth is less than ²/₃₂ “. If any of his head is obscured, your tire is good to go.
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3. Quarter Test
a. Sit comfortably next to the tire so that you can clearly see the tread.
b. Hold the quarter with Lincoln’s head facing you and with the head pointing at the surface of the tire.
c. Drop the quarter into the grooves of the tread until it can go no further.
d. If the height of the tread block touches Lincoln’s head, then you have approximately ⁴/₃₂” of tread left. This means the tire is still legal, but it’s getting very close to its legal limit, and you should be making plans to replace it.
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4. Tire Tread Gauge
b. Push the end of the gauge that has the scale on it so that the other end is sticking out of the gauge’s barrel.
d. If you have a manual gauge:
i. Slowly rotate the scale until you see the first number, where a line is clearly visible underneath it.
ii. The scale is printed in measures of ¹/₃₂”. This means that the number is the depth of your tread in multiples of ¹/₃₂”. So if your gauge reads 5, then the tread depth is ⁵/₃₂” deep, and it’s still legal, but if it’s ²/₃₂”, it’s illegal and dangerous.