The tires on your vehicle are what can assure you a safer driving experience and a more comfortable ride. Maintaining the tires means inflating them to their correct tire pressure, maintaining their alignment, keeping the wheels balanced and inspecting the depth of tire treads. The latter, tire tread, is a very important indicator of tire integrity and vehicle performance. With this in mind, it is critical to check tire treads on a more frequent and regular basis. Understanding the 7 different types of tire tread wear can help you determine whether you need a set of brand-new tires or have the wheel aligned.
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The Importance of Tire Tread Wear
Before we start talking about the 7 types of tread wear, let us first understand the importance of tire treads.
On a flat, even, and dry pavement, you don’t need tires with treads. Take a look at the racecars of Formula 1. These are slick tires that contain no groves or treads. The entire surface of the tire is in constant contact with the surface of the race track. The softer the compound is, the better is its grip on the road. This translates to the car’s ability for higher speeds. However, as soon as the weather changes, F1 race teams change their tires into intermediates or wet tires. These have grooves or treads. This allows F1 race cars to still blitz the course without sliding.
We cannot have slick tires on our vehicles in the real world. This is because we are at the mercy of the elements at any given point in time. We can run over a puddle of water on the road. There might be a light drizzle a few blocks from where we’re driving. Gravel, sand, even the simple road dirt would make the tire lose grip. In other words, it is very difficult to predict what kind of environment we will be facing on our drive ahead.
If there is water or snow on the road surface, this will get in between the rubber of the tires and the road itself. The pressure of water will lift the tires a fraction of a millimeter off the surface of the road. When this happens, the tires will lose contact with the ground. This loss of grip or traction can lead to a loss of control of the vehicle. You can skid and increase your risk of figuring in an accident.
Hence, real-world tires operate on the same principle as intermediate racing tires. They need to have grooves in the rubber to help channel water away from the tires. These grooves are where water will push through instead of against the contact patch of the tires. Sideward grooves will then channel the water away from the central grooves. This way, water and snow will move towards the outside of the tires.
Since water is now pushed or channeled away from the tires, the rubber contact patch of the tires maintains traction on the road. This helps prevent skidding and loss of vehicle control.
This is the fundamental reason why tires of road vehicles should have treads or grooves. If there is uneven or excessive wear of the tire treads, it will be almost similar to driving with racing slicks. This reduces the tire’s ability to maintain grip or traction of the road surface.
Hence, the shallower the tread or groove, the greater is the tendency for water to push the tire off of the surface of the ground. This can lead to hydroplaning and the loss of control of the vehicle.
Minimum Depth of Tire Tread
Tire makers in the US express the depth of their tire treads in 32nds of an inch. A brand-new tire will often come with a tread depth of about 9/32 to 11/32 inches. Many states put the minimum tire tread depth of 2/32 of an inch or about 1/16 of an inch. What this means is that vehicle owners should replace their tires if their tread depth is already below this minimum.
Different tire manufacturers can also make recommendations as to when automobile owners need to replace their tires. For instance, Bridgestone considers a 2/32-inch tread depth to be a good indicator of tire replacement. Understand that it doesn’t say less than 2/32 inches. What Bridgestone is saying is that if your tire tread depth is already at the 2/32 inch level, then you should replace it at once.
There are several ways in which you can determine if your tire’s tread depth has already reached its limit. Modern tires already come with wear bars. These are tire tread depth indicators that are present within the grooves of the tire. Brand new tires will have these wear bars deeper into the groove. Over time, as the rubber wears, these bars come closer to the outer surface of the tire. Once it is already flush with the tread ribs, it means you’ve reached your tire’s minimum tread depth.
If you cannot find the tire tread depth indicator bars in your tire, a reliable way to evaluate the tread depth is by using a penny. The US penny features Abraham Lincoln’s bust. Take note of the top of Lincoln’s head. Also take note of the imaginary section between the top of Lincoln’s head and his hairline.
Get a penny and turn it upside down so that you are inserting Lincoln’s head first in the tire tread. If the tire rib is in level with Lincoln’s hairline, this means you still have more than 2/32-inch tread depth. However, you may have to replace your tire soon. If the tire rib is in level with the top of Lincoln’s head, then you are still at the minimum 2/32-inch tread depth. It is a general recommendation to replace your tire if you get to this point. However, if you can see the whole of Lincoln’s head, that means you have to replace your tire at once. If you cannot see Lincoln’s hairline, your tire still has plenty of miles to go.
7 Types of Tire Wear
We now have an understanding of the importance of tire treads and how to check for the depth of our tire’s treads. The next thing we have to learn now is the different types of wear that we can expect from our tires. It’s also important to know what can cause these types of changes to the tire so we can make the necessary corrective measures.
- Center Rib Wear
Center rib tire wear is always an indication of overinflated tires. Overinflating the tires can increase the pressure within the inner walls of the tire. This increase in air pressure makes the inner walls stiffer, which can lead to a reduction in the tire’s overall performance.
One very obvious ill effect of overinflating tires is the reduction in the contact patch. The increase in air pressure will cause the center rib of the tire to bulge. This shifts the contact patch of the tire to the center instead of being distributed across the entire width of the tire. The reduction in contact patch will also make the engine compensate. This can lead to a reduction in fuel economy.
Overinflating the tires can also have an impact on vehicle safety and ride comfort. Since the contact patch is on the center rib of the tire, it can result in an unstable ride. Vibrations also get transmitted a lot easier through the rest of the vehicle. This occurs because there is less tire surface that is able to absorb bumps and shocks from the road.
Hence, if you see excessive wear in the center section of your tire, it only means you’ve been overinflating it.
- Side or Both Shoulder Wear
Tires that show excessive wear on the sides or shoulders are often the result of underinflation. This is the opposite of a center rib wear. As such, if there is not enough air pressure inside the tires, the tendency is for air to move towards the sides. This is because air will always move to an area with the least resistance.
If you are constantly underinflating your tire, you’re not only courting shoulder or side wear. You are also risking tire failure. This occurs because an underinflated tire increases the tire surface area in contact with the ground. The problem with this is that it also increases friction, which can lead to the tire overheating. It is not uncommon to hear underinflated tires resulting in tread separation and blowouts.
There is another reason why an underinflated tire is not good. If one tire is underinflated, this side of the car exerts more pressure on the vehicle components in this section. It can damage the suspension system, the brake lines, the calipers, and the brake rotors. It is also possible to damage the chassis itself.
Underinflated tires also beget poor handling of the vehicle. It would be more difficult to maneuver the car around tricky situations such as those requiring sudden evasive action.
Now, there are also instances when shoulder tire wear occurs despite using the correct tire pressure. In such cases, the problem may be due to a worn or bent steering arm. It is also possible that the car’s wheels are out of alignment. In any case, a mechanic can help you diagnoses such issues so you’ll know what to do.
- Cupping Wear
Cupping is a very peculiar type of tread wear. You will notice patchy worn out sections on your tire. This is often brought about by the irregular up and down movement of the wheel, as if it is bouncing. Some people call this type of wear scalloping since the worn bits look more like a 3 to 4-inch diameter scallop. The cupped or scalloped tire can produce a very distinct rumbling noise at high speeds. At slower speeds, the ride can be very harsh or bumpy.
There are 4 possible reasons why cupping or scalloping can occur. These can include a problem with the car’s suspension parts or shock absorbers. It can also be because of poor wheel alignment or tire imbalance. Cupping can also develop because of poor-quality tire construction.
A bad suspension or shock absorber can put undue strain on the tires. Instead of the suspension system absorbing the forces from the road, the tires take some of it. Some sections of the tire will experience greater friction than others, causing scalloping in these areas.
Scalloping can also occur if there is a problem in wheel alignment. For instance, if the front and rear tires are not aligned in such a way that they are parallel to one another, then cupping can occur. Misaligned toe angles can also produce cupping that can take on a more diagonal pattern.
Tire imbalance can produce a very bumpy ride at speeds higher than 45 MPH. This bouncy ride can produce cupping wear on the tires. Tire runout, too, can cause scalloping. Poor quality tires often have thinner walls and less thread. They are more susceptible to misshaping and imbalances. In other words, mediocre tires can produce scalloping wear.
- Feathering
This is a type of uneven tread wear that is not that easy to spot on visual inspection. In most instances, you will need to run your fingers across the surface of the tire. You will feel a worn tread on one side while the other side is sharp.
Feathering is almost always an issue with improper wheel alignment, especially excessive caster and toe settings. It can be excessive toe-in or excessive toe-out settings. The good thing with this type of wear is that it’s easy to remedy with wheel realignment. Of course, if the worn-out side has already lost its traction capabilities, then you will have to replace the tire itself.
Feathering can also be due to aggressive driving habits. For example, turning at corners at high speeds can produce the classic combination of low and high sections on the tire rib.
- Flat Spot Wear
Flat spot tire wear is almost always an indication of brake problems. It can be a real brake issue or one that the driver initiates himself. For example, driving the brake pedal straight to the floor to avoid hitting an object can lead to skidding. The sudden application of brakes stops the wheels from turning. However, this doesn’t stop the forward momentum of the car. As such, the “stationary” tire will rub against the surface of the road. That section of the tire that skidded or made contact with the road will develop what is known as flat spot wear.
It is also possible that flat spot wear will occur in normal braking conditions. If you can be sure that you have never made any hard stops ever in your life, then the most likely culprit is a failing brake system. In such a case, the flat spot wear is a manifestation of a more serious problem.
It is best to bring your car to your mechanic so he can check the condition of your brake system. Feathering is easy to fix with a simple realignment. The same is not true with flat spot wear. Once you see this on your tire, it’s a guarantee that you’ll have to replace your tire.
- One Side or One Shoulder Wear
If only the outer edge or the inner edge of the tire has visible signs of wear, they call this a one-sided wear. If the wear is on the outer edge of the tire, it is often brought about by positive camber, toe, and caster. However, if there are no issues in your car’s wheel alignment, it is possible that outer-edge wear is due to overenthusiastic cornering. You may be surprised to know that this is the leading cause of outer-edge tire wear.
If the wear occurs only on the inner edge of the tire, this is most often brought about by negative camber and toe settings. It is also possible that there may be issues in your car’s springs, bushings, ball joints, and loads.
Having a mechanic check these parts or perform a realignment of your tires can correct the issue.
- Sidewall Wear
As the name implies, this type of wear occurs at the sidewall of the tire. There is only one cause for this and is often associated with poor driving and parking habits. Scraping the tires against the curb can cause this type of tire wear. This can occur whether one is driving or parking the vehicle. As the tire rubs against the curb, a layer of the tire can get scraped off.
Sidewall wear can weaken the core of the tire. Air pressure can exert greater force in this section since it is “thinner” than the rest of the tire. In severe cases, the tire can buckle and lead to tire failure.
Many of these tire tread wear patterns are due to bad driving habits, poor tire inflation practices, and improper balancing of the tires. Making sure you drive as responsibly as you can while adhering to the correct tire inflation pressures and wheel alignment can help you extend the life of your tires.
Sources:
- Understanding Tire Wear – Know Your Parts
- How To Read Tire Wear Patterns & Improve Your Safety – Firestone Complete Auto Care
