The tyres on your vehicle can assure you a safer driving experience and a more comfortable ride. Maintaining the tyres means inflating them to their correct tyre pressure, maintaining their alignment, keeping the wheels balanced and inspecting the depth of tyre treads. Abnormal tyre wear, such as feathered directional wear pattern, cupped wear pattern, centre of the tread more worn than the shoulders, and shoulders more worn than the centre, can indicate potential issues like misalignment or unbalanced wheels. With this in mind, checking tyre treads more frequently and regularly is critical. It is important to check tyres regularly for signs of abnormal wear, at least once a month when the tyres are cold, to spot early signs and prevent unexpected incidents. Understanding the seven different types of tyre tread wear can help you determine whether you need a set of brand-new tyres or have the wheel aligned.
The Importance of Tyre Tread Wear Indicators
Before we discuss the seven types of tread wear, let’s first understand the importance of tyre treads.
On flat, even dry pavement, you don’t need tyres with treads. Take a look at Formula 1 racecars. These are slick tyres that contain no groves or treads. The entire surface of the tyre is in constant contact with the race track’s surface. The softer the compound, the better its grip on the road. This translates to the car’s ability to drive at higher speeds. However, as soon as the weather changes, F1 race teams change their tyres into intermediates or wet tyres. These have grooves or treads. This allows F1 race cars to still blitz the course without sliding.
We cannot have slick tyres on our vehicles in the real world. This is because we are at the mercy of the elements at any given time. We can run over a puddle of water on the road. There might be a drizzle a few blocks from where we’re driving. Gravel, sand, or superficial road dirt would make the tyre lose grip. In other words, predicting what kind of environment we will face is tough on our drive ahead.
If there is water or snow on the road surface, this will get in between the rubber of the tyres and the road itself. Water pressure will lift the tyres a fraction of a millimetre off the road’s surface. When this happens, the tyres will lose contact with the ground. This loss of grip or traction can lead to losing vehicle control. You can skid and increase your risk of getting into an accident.
Hence, real-world tyres operate on the same principle as intermediate racing tyres. They need grooves in the rubber to help channel water away from the tyres. These grooves are where water will push through instead of against the contact patch of the tyres. Sideward grooves will then channel the water away from the central grooves. This way, water and snow will move towards the outside of the tyres.
Since water is now pushed or channelled away from the tyres, the rubber contact patch maintains traction on the road, helping prevent skidding and loss of vehicle control.
This is why road vehicle tyres should have treads or grooves. If the treads wear unevenly or excessively, driving with racing slicks will be similar. This reduces the tyre’s ability to maintain grip or traction on the road surface.
Tyre tread wear indicators help determine when tyres should be replaced by showing the level and pattern of tread wear.
Hence, the shallower the tread or groove, the greater the tendency for water to push the tyre off the ground’s surface. This can lead to hydroplaning and the loss of control of the vehicle. Incorrect tyre pressure can also cause uneven tread wear patterns, affecting vehicle performance and safety.
Minimum Tread Depth of Tire Tread
Tyre makers in the US express the depth of their treads in 32nds of an inch. A brand-new tyre often has a tread depth of about 9/32 to 11/32 inches. Many states set the minimum tyre tread depth at 2/32 or about 1/16 inch. This means vehicle owners should replace their tyres if their tread depth exceeds this minimum.
Different tyre manufacturers can also recommend when automobile owners must replace their tyres. For instance, Bridgestone considers a 2/32-inch tread depth a good indicator of tyre replacement. Understand that it doesn’t say less than 2/32 inches. Bridgestone says that if your tyre tread depth is already at the 2/32-inch level, you should replace it immediately.
You can determine if your tyre’s tread depth has reached its limit in several ways. Modern tyres already come with wear bars. These are tyre tread depth indicators that are present within the grooves of the tyre. Brand-new tyres 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 tyre. Once it is flush with the tread ribs, you’ve reached your tyre’s minimum tread depth.
If you cannot find the tyre tread depth indicator bars in your tyre, 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, please take note of the imaginary section between the top of Lincoln’s head and his hairline.
Get a penny and turn it upside down to insert Lincoln’s head first in the tyre tread. If the tyre rib is level with Lincoln’s hairline, you still have more than 2/32-inch tread depth. However, you may have to replace your tyre soon. If the tyre rib is 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 tyre if you get to this point. However, if you can see the whole of Lincoln’s head, you must replace your tyre immediately. If you cannot see Lincoln’s hairline, your tyre still has many miles.
To ensure your tyre safety, consider taking advantage of a free tyre check service. This complimentary service can help you identify signs of abnormal wear and provide guidance on how to address various wearing patterns.
7 Types of Tire Wear
We now understand the importance of tyre treads and how to check for their depth. The next thing we must learn is the different types of wear we can expect from our tyres. It’s also important to know what can cause these types of changes to the tyre so we can take the necessary corrective measures.
Center Rib Wear
Center-rib tyre wear is always an indication of overinflated tyres. Overinflating tyres can increase the pressure within the inner walls, making them stiffer, which can reduce the tyre’s overall performance. It is crucial to maintain correct tyre pressure for both front and rear tyres to ensure optimal performance and safety.
One noticeable ill effect of overinflating tyres is a reduction in the contact patch. The increase in air pressure causes the tyre’s centre rib to bulge, shifting the contact patch to the centre instead of being distributed across the entire width of the tyre. The reduction in contact patch also causes the engine to compensate, which can reduce fuel economy.
Overinflating tyres can also impact vehicle safety and ride comfort. Since the contact patch is on the tyre’s centre rib, it can result in an unstable ride. Vibrations are also transmitted much more quickly through the rest of the vehicle. This occurs because less tyre surface can absorb bumps and shocks from the road.
Hence, if you see excessive wear in the centre section of your tyre, it only means you’ve been overinflating it.
Side or Both Shoulder Wear
Tyres that show excessive tyre wear on the sides or shoulders are often the result of underinflation, which is the opposite of centre rib wear. If there is not enough air pressure inside the tyres, air tends to move towards the sides. Air will always move to an area with the least resistance.
If you constantly underinflate your tyre, you’re not only courting shoulder or side wear. You are also risking tyre failure. This occurs because an underinflated tyre increases the tyre’s surface area in contact with the ground. The problem with this is that it also increases friction, which can lead to the tyre overheating. It is expected to hear underinflated tyres, which results in tread separation and blowouts.
Another reason an underinflated tyre is terrible is that if one tyre is underinflated, this side of the car exerts more pressure on the vehicle components in this section. This can damage the suspension system, the brake lines, the callipers, and the brake rotors, and it is also possible to damage the chassis itself.
Underinflated tyres also result in poor vehicle handling. It is more challenging to manoeuvre the car around tricky situations, such as those requiring sudden evasive action.
There are also instances when shoulder tyre wear occurs despite using the correct tyre 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. A mechanic can help you diagnose 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 tyre. 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 tyre can produce a distinct rumbling noise at high speeds. At slower speeds, the ride can be very harsh or bumpy.
Four possible reasons for cupping or scalloping are problems with the car’s suspension parts or shock absorbers, poor wheel alignment, tyre imbalance, or poor-quality tyre construction.
A lousy suspension or shock absorber can put undue strain on the tyres. Instead of the suspension system absorbing the forces from the road, the tyres take some of it. Some tyre sections will experience greater friction than others, causing scalloping in these areas.
Scalloping can also occur if there is a problem with wheel alignment. For instance, if the front and rear tires are not aligned parallel to one another, then cupping can occur. Misaligned toe angles can also produce cupping that can take on a more diagonal pattern.
Tyre imbalance can produce a very bumpy ride at speeds higher than 45 MPH, which can cause cupping wear on the tyres. Tire runout, too, can cause scalloping. Poor-quality tyres often have thinner walls and less thread, making them more susceptible to misshaping and imbalances. In other words, mediocre tyres can produce scalloping wear.
Feathering
This is a type of uneven tyre tread wear that is not easy to spot on visual inspection. You must often run your fingers across the tyre’s surface. You will feel 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, you will have to replace the tyre.
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 tyre rib.
Flat Spot Wear
Flat spot tyre wear is almost always an indication of uneven tyre wear caused by brake problems. It can be a natural brake issue, or 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” tyre will rub against the road’s surface. That section of the tyre 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 severe 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 accurate with flat spot wear. Once you see this on your tyre, it’s a guarantee that you’ll have to replace it.
One Side or One Shoulder Wear
If only the outer or inner edge of the tyre has visible signs of wear, they call this camber wear. If the wear is on the outer edge of the tyre, it is often brought about by positive camber, toe, and caster. However, if there are no issues in your car’s wheel alignment, outer-edge wear may be due to overenthusiastic cornering. You may be surprised that this is the leading cause of outer-edge tyre wear.
If the wear occurs only on the inner edge of the tire, this is most often caused by negative camber and toe settings. Issues in your car’s springs, bushings, ball joints, and loads may also be a factor.
A mechanic checking these parts or realigning your tyres can correct the issue.
Sidewall Wear
As the name implies, this type of wear occurs at the tire’s sidewall. There is only one cause for this, often associated with poor driving and parking habits. Scraping the tyres against the curb can cause this type of tyre wear, whether one is driving or parking the vehicle. As the tyre rubs against the curb, a layer of the tyre can get scraped off.
Sidewall wear can weaken the tyre’s core. Air pressure can exert more significant force in this section since it is “thinner” than the rest of the tyre. In severe cases, the tyre can buckle and lead to tyre failure.
These tread wear patterns are due to impaired driving habits, poor tyre inflation practices, and improper balancing. Driving responsibly while adhering to the correct tyre inflation pressures and wheel alignment can help you extend the life of your tyres.