Tire Wear Bars: What are They & How to Read Them?
Posted by Priority Tire on Jun 3rd 2021
Have you ever noticed the small bars in the grooves of your tires and wondered what they are for?
Well, as it turns out, they are not just for show. They play an important role in not just the tire's treadwear measurement but are also used to increase the tires' traction and performing capabilities.
Let's take a look at precisely why they need to be on your passenger car and SUV tires.
Tire Wear Bars (Tread Wear Bars)
Tire or tread wear indicator bars are located in the tread grooves. They are the raised bars that connect one rib to the other (or are between the tread blocks). Wear indicator bars are placed around the tire at different parts of the tread. Their main function is to show how much tread is left on the tires and to indicate when the tires need to be replaced.
During the tire's lifetime, the entire tire footprint is wearing out. You can check the remaining treadwear rate left on your tires by checking how far the tread is from these treadwear bars. Generally speaking, tires are considered to be worn out, once their tread reaches the tire wear bars.
Tire wear bars sit at 2/32" of tread depth, which is the lowest tread depth allowed by the law - this depends on state to state, but most in most states you can drive your vehicle with that much tread left.
Tread wear indicator bars help you visually measure the tread depth left on your tires. However, their visual indication of the tread life left on the tires is approximate. They do not provide you with exact measurements, they only show you the point where the tires need to be changed. Therefore, additional tread depth measurements are recommended.
Why are Tread Wear Bars Necessary?
Apart from their visual indication of the tire tread, they also have functional tasks.
As they are located between the tread elements, they also secure the tire tread during its performance. This greatly reduces tread movement and flexing while the tires are in motion, which increases the traction and the performing ability.
The tread stability allows the tire to have better surface grip in wet and winter weather conditions (on slippery road surfaces), while it upgrades the cornering and braking abilities with the optimized traction provided.
Worn tires, which reach the 2 32nds of an inch depth, have significantly diminished performing capabilities. Their worn-out tread is not able to provide the needed surface grip for maneuvering, which can lead to dangerous consequences.
Therefore, tire wear bars visually show you when you need a new set of tires, while increasing your vehicle's performing safety in different weather situations.
Tire Wear Indicators
Tire wear indicators are technologies and tread designs utilized by the manufacturers. They also show the treadwear rate of the tires in a visual manner, but they provide a more accurate reading.
Most manufacturers will place numbers around the tire, that indicate either the tread depth in 32/inch or in percentages. These numbers rub out along with the tire tread throughout the tire's lifespan. This allows you to follow the treadwear, and to precisely measure the depth of the tires at all times.
Not all brands use numbers as tread wear indicators. Some manufacturers use their own designs or different words to help you measure the tread depth and see when new tires should be purchased.
For example, Continental's DW and DWS indicators show the tire's performing traction ability. D, W, and S stand for Dry, Wet, and Winter (Snow) traction and these letters will wear with the tread. When the W disappears the tire no longer has a good winter grip. Once the tread reaches the D, it is only good in dry conditions and it can be considered to be worn out.
On the other hand, General Tires' Replacement Tire Monitor literally placed these words on the new tires' center rib. The letters wear with the tread as we have mentioned before. However, here the words will change to "Replace Tire" when the tire is not able to provide the needed surface grip anymore.
In both examples, when the treadwear indicator shows the tire's tread is worn-out, it is time to replace your tires.
How to Check Tire Wear Without Bars?
There are various tread-checking methods you can use in order to see the remaining depth of your tires. The most popular ones are using a tread gauge and the penny test.
Tread gauges come in different shapes and sizes and most can be purchased at your local auto parts store and at versatile retail stores. Their quality and accuracy can be vastly different, so it is recommended to get a better one if you are in the market for a tread gauge.
To use the penny test, on the other hand, you only need a penny. This method is not as accurate as using a tread gauge, but desperate times call for desperate measures. You place the penny into the tread groove and based on where the tread ends compared to Lincoln's head, you can see the remaining tread depth of your tires. While the penny test is not really precise, it will still give you an approximate estimation of when you should get new tires for your vehicle.
If you do not wish to purchase a gauge or do not want to use Lincoln's head, the safest way to check the tread is to take your vehicle to the mechanic. They will be able to tell you when your tires should be replaced based on their tread measurement.
If you are interested in a more in-depth explanation about different ways to measure the tire tread, be sure to check out our blog post.
Frequently Asked Questions (FAQ)
How deep is the wear bar on a tire?
The tread wear bars on a tire sit precisely at 2/32". This is the minimum allowed tread depth on the tires. Tires with less tread are unsafe to be driven on and, in most states, they will not pass the vehicle's inspection.
When a tread wear bar appears on a tire you should?
When a treadwear bar appears on a tire, it visually indicates the end of the tire's safe usability. In such cases, you will need new tires, as the current ones will no longer provide the necessary traction for secure performance.
Should I replace tires before wear bars?
You should replace your tires before they reach the wear bars. The tire bars only show the legal lowest tread allowed on the tires, but most tires will lose their driving safety way before the tread is worn-out. For that reason, a new set of tires will be needed to ensure the safety of your vehicle.