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About Tire Tread Depth
Tires provide the main point of contact between the vehicle and the ground. And their tread grips the surface as you drive. However, if the tread is not deep enough, it’s highly likely that your vehicle will lose grip, leading to longer braking distances.
Furthermore, a shallow tread will make it extremely hard to control or handle a vehicle in wet conditions, due to increased hydroplaning. Therefore, you may easily end up crashing in rainy conditions.
To prevent such issues, it’s important to measure your tire tread depth regularly, to ensure they are safe for driving. On average, new tires come with a tread depth of around eight to nine millimeters. And if you were to use 32nds of an inch, then a new tire will have 10/32-inch to 11/32-inch of the tread.
Any tire with a tread depth of below 2/32-inch of tread is considered unsafe for driving. And you should replace it right away.
How to Measure Tread Depth
As noted above, it’s important to measure your tire’s tread depth regularly, to ensure it has enough depth to guarantee safe driving. So, how do you measure tire tread depth? Well, you have several methods that you can use. They include:
The Penny Test
The penny test is arguably one of the easiest methods to measure tread depth and determine whether you’ve hit the minimum 2/32-inch of tread allowed by the U.S. Department of Transportation.
For the penny test, you simply need to insert a penny on your tire's tread ribs. The rib is the raised part of a tread, running longitudinally to the tire. When using this test, Lincoln’s head on the penny should be pointing down into the tire’s tread.
If Lincoln’s head disappears completely between the tire’s ribs, then the tread depth is well above the 2/32-inch threshold. In case the head is visible, even slightly, you should start making plans of replacing the tire. And if the entire head is visible, then the tire has hit the 2/32-inch threshold, and you should replace it right away.
When using this method, make sure you inspect other areas of the tire. Check whether the tread wear is uniform. Also, inspect the tire and look out for areas that may be extremely worn. As much as the tire may still have adequate tread depth, it may still fail, if it’s severely worn in other areas. In case the tire is uniformly worn or it has signs of extensive damage, you should take the vehicle to your technician right away, for further inspections.
Tread Depth Gauge
A tread depth gauge provides yet another simple but reliable means of measuring tire tread depth. Tire tread depth gauges are sold in almost all auto parts stores. You have plenty of options to choose from, depending on your budget.
Once you’ve acquired one, you simply need to insert its probe into a tire’s tread grooves, press its shoulders and then read the result on the gauge. All gauges come with millimeter readings as well as 32nds of an inch reading.
Treadwear Maintenance Indicators
Every DOT-approved tire sold in the U.S comes with treadwear maintenance indicators. Treadwear maintenance indicators are a series of rubber bars, placed deep inside the tire’s tread grooves.
They are usually placed there to help drivers monitor their tire’s level of treadwear easily. A tire should be replaced if these narrow rubber bars flush with the tread.
It’s important to note that winter tires follow different tread depth requirements. Therefore, they feature special winter tire wear indicators. In case the narrow bars flush with the tire’s tread, then such a tire is not considered safe for winter driving. While it may still have more than 2/32-inch of tread, it may not supply adequate grip and traction for winter driving conditions.
Tire Tread Depth and Stopping Distances
As mentioned earlier, a tire’s tread depth will affect its braking performance. Tires whose tread is almost completely worn out will have longer braking distances, compared to new tires. But on average, you can expect a stopping distance of 185 feet for a tire with a tread depth of 6/32, 205 feet for 4/32 tread depth and approximately 250 feet or even more for tread depth of 2/32. As you can see, it’s extremely dangerous to drive with a tire whose tread depth is below the minimum threshold.
Tips for Extending Tire Tread Life
At some point, your vehicle’s tires will wear out completely and reach the minimum 2/32-inch tread depth. However, there are a couple of things that you can do, to extend tire tread life.
Ensure they are Properly Inflated
Inflation pressure is one of the biggest determinants of tire tread life. Driving with tires at 20% below the recommended inflation pressure can considerably reduce their mileage, by approximately 16%, even when are driving at normal speeds.
Every tire comes with specific inflation pressure. So, before you head out, always make sure you check your tires, to ensure they have the right air pressure. And if you can’t do it every day, then you should be checking them at least thrice per week.
Go for Tire Rotation after Every 5,000 Miles
Most vehicles on the road use two wheels at a time. And this can contribute to uneven tread wear, thus prompting their removal from service prematurely. For instance, if you drive a rear-wheel vehicle, the rear wheels will wear out faster than the front ones. And if you drive a front-wheel vehicle, then the front wheels will wear out faster than the rear ones.
To prevent such issues, you should go for a tire rotation every 5,000 miles or so. A technician will move the tires around, thus making sure they wear out uniformly. Furthermore, rotation can help to improve your tire’s tread life.
Keep Your Vehicle Properly Aligned
Vehicle misalignment is one of the leading causes of irregular tread wear. Simply put, if your vehicle is not properly aligned, then the tires will not run straight ahead. Consequently, their tread wear rate will be higher, compared to a vehicle whose tires are running straight. To prevent irregular tread wear, make sure your vehicle is properly aligned at all times.
Ideally, you should take your vehicle for an alignment check at least twice every year. If there are any alignment issues, your mechanic will detect them early enough and correct them, thus ensuring your tires are running straight.
Replace Tires with Identical Ones
Your vehicle should always run on an identical set of tires until they wear down to their treadwear indicators. However, you may sometimes be forced to replace one or two tires, which have been removed from service due to workmanship defects, road hazards or irregular wear. In such a situation, you should make sure the replacement tire is identical to the existing ones. Driving on an identical set of tires will ensure uniform tread wear, again helping to extend your tires’ tread life.
Avoid Driving at Excessively High Speeds
Whenever you are driving on the highway, you may sometimes be tempted to drive at the maximum speed limit allowed. While it may be a thrilling experience, you will also be increasing your tire’s treadwear rate.
High-speed driving will generate more heat for the tires, thus degrading the rubber compound used to make them faster. And if you do it often, you will be forced to replace your tires sooner than someone who drives at average speeds.
Wrapping It Up
Tire tread depth determines various areas of a vehicle’s handling and performance. If the tread depth is above the recommended threshold, then the tire will deliver reliable traction and short braking distances on a wide range of road surfaces. Hence, it’s highly advisable to keep checking your tires’ tread depth regularly to ensure the remaining tread can provide a safe driving experience. And as you can see, you have several methods of doing so.
About The Author
I've spent many years selling cars, working with auto detailers, mechanics, dealership service teams, quoting and researching car insurance, modding my own cars, and much more.Read More About Charles Redding