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Understanding Tire Tread Wear Can Tell You About Your Car

Here’s the fact:

Your car tires will inevitably wear out. On average, you should get 50,000 miles out of an auto tire before you have to replace it.

understanding tire tread wear patterns and causes

Source: http://www.kinkarso.com/

BUT...

It is possible for a tire to have premature tread wear. Of course, part of it would be due to the certain friction, pressure, and weight bearing that the tire has to sustain when your car is in motion. But it may also be due to issues in other areas of your vehicle—say a faulty suspension system.

Car tire wear occurs in different patterns. And each pattern can say a lot about the state of a tire and other related parts of your vehicle.

In this guide, we discuss 10 of the commonest car tire tread wear patterns.

  • What are they?
  • How do you identify them?
  • What are their causes and solutions?

First, we should do a quick exposition on tire tread.

Tire tread wear: What is it all about and why does it matter?

A tire tread is the rubber on the circumference (or fringes) of tire, which makes contact with the ground or road.

A tire tread may be bare, like that of a racing slick (slick tire), pictured below.

racing slick

Image: https://www.quora.com/profile/Muhammed-Roshan-1

Or, it may have a pattern of grooves molded into the rubber, like that of your average car tire, pictured below.

grooved tires

https://www.quora.com/Why-did-F1-shift-from-grooved-tires-to-slick-tires

A tire without a tread pattern (or simply pattern) is often called a slick tire, while a tire with a pattern is aptly called a grooved tire. It is important not to confuse the tread for the tread pattern, as they’re often used interchangeably. Here’s an image of both tire types placed side by side:

slick vs grooved

Source: https://www.reddit.com/r/NASCAR/comments/26ev12/what_was_with_the_grooved_tires/

Regardless of the type of tire, the tread will wear off with continued usage. And this limits the effectiveness of the rubber in providing traction.

In grooved tires, tire tread wear may be observed as disappearing patterns (referred to as pattern wear) or direct tread wear (where the pattern may still be intact).

Tire tread depth

Every car tire has a range of markings, codes, and specifications that provide numerous specific information. From the tire’s load rating to the date it was manufactured.

tire markings

Source: https://en.wikipedia.org/wiki/Tire_code#/media/File:Tire_code_-_en.svg

The manufacturer’s date is particularly noteworthy as the expected service life of a tire ranges between 6 and 10 years. However, should you want to pin down just when you should replace a tire, you should pay attention to the tread depth spec.

In grooved car tires, it is the distance between the top (or highest point) of the rubber (or tread) and the bottom of the deepest groove.

The tread depth of new all-season tires typically ranges from 9/32-inch to 11/32-inch. However, with continued use, the tire depth expectedly reduces. The minimum tread depth requirement in most states is 2/32-inch. At this point, it is necessary to replace the tire.

Ideally, you’d need a tire tread depth gauge to measure the tire depth accurately. But there’s a basic, reliable hack to tell if a tire has reached the 2/32-inch threshold—the penny test.

The penny test is simple.

  • Place a penny into a groove (between tread ribs) with Lincoln’s head upside down
  • Then observe the visibility of Abe’s head. If you can’t see the top of Abe’s head between the ribs, the tread depth is still above the 2/32-inch threshold
    However, if you can see the top of Abe’s head (Lincoln’s whole head), the tread depth has hit the threshold and you should replace the tire
the penny test

Source: http://www.tireamerica.com/research/the-penny-tire-test

That said, let’s explore the commonest car tire issues that may have you reaching for a penny.

10 Tire Tread Wear Patterns

Center tread wear

center tread wear

Source: http://mservice411.com/

What else is it called?

Center wear, center rib wear.

How does it appear?

The tread pattern wear occurs exclusively at the center or middle of the tire. While the tread pattern on the left and right edges seem relatively normal, the pattern down the middle would appear smoother. In extreme cases, it’d have an almost bald appearance.

What are the likely causes?

  • Over inflation. Overinflating a tire (putting in too much air) would cause the middle or center section to bulge. During motion, the tire’s bulging center gets more in contact with the road than the sides. This would cause the tread at the center to wear faster
  • The wheel and tire are not properly matched. Overinflation is often the causative factor of center wear. But if you’ve ruled it out, then a mismatch of the wheel and tire is the likely cause
  • Sometimes however, center tread wear may be a normal occurrence in some high-powered sports rear-wheel-drive cars

What are the risks?

  • Compromised traction and braking
  • Enhanced risk of blowouts as bald tread strips can’t dissipate heat effectively

What do you have to do?

  • Adjust or deflate your tires to the pressure (PSI) specification recommended by your manufacturer. You’d find this pressure specified in your owner’s manual or the sticker in the driver’s door jamb of your car
    Do not disregard the manufacturer’s recommended pressure in favor of the ‘max. press’ embossed on the tire’s sidewall. The pressure rating on a tire’s sidewall is the maximum safe pressure. It is not a recommendation
  • If the tire’s pressure checks out correctly, you’d need to head to an auto repair center to match the wheel and tire properly. Or confirm if you are in need of a different type of tire

Outer tread wear

outer edge wear

Photo: http://www.e90post.com/forums/showthread.php?t=311731

What else is it called?

Outer-edge wear, shoulder wear.

How does it appear?

Tread pattern wear occurs at both edges (inner and outer edges) of the tire, while the pattern at the middle is relatively normal.

What are the likely causes?

  • Underinflation. As more of the tire tread gets in contact with the road
  • Compromised ride quality
  • Overly aggressive cornering
  • ban
    Excessive positive caster/camber and toe

What are the risks?

Under inflation (characterized by too little pressure) is associated with significant risks and danger.

The major risk from an under-inflated tired is the possibility of a blowout. This is because an underinflated tire flexes more than a properly inflated tire and so experiences an unsafe build-up of heat. This combination places an underinflated tire at higher risk of a blowout.

Other risks include:

  • The wheel being forced out of alignment
  • Not being able to absorb bumps well, which may lead to damage to the suspension
  • Tire lifespan is reduced by at least 15%
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    Fuel economy is decreased by as much as 15%, as the underinflated tires make the engine work harder

What do you have to do?

The solution is simple enough: ensure your tire is properly inflated at all times. Many cars have a tire-pressure monitoring system that’d help you keep close tabs on your tires’ pressure effortlessly.

However, you shouldn’t rely on it completely. Several TPM systems only alert you when a tire’s PSI is 25% underinflated. The quirk with this threshold is that the pressure may get dangerously low to a level that could destroy a tire before the warning light comes up.

For example, a tire that should be at 28 psi may be at 22 psi before you notice the warning light.

It is preferable to check a tire’s pressure monthly.

One-sided wear

one sided wear

Photo: http://www.y-yokohama.com/

What else is it called?

Single-side wear, one shoulder wear.

How does it appear?

As the name implies, tread pattern wear is exclusive to one side (edge or shoulder) of the tire.

What are the likely causes?

The primary cause of single-side wear is wheel misalignment. This may be down to:

  • the camber [angle] settings being off. This results in the tire leaning away from or toward the vehicle. As a result, the tire tread on the side that makes more contact with the road wears out faster
  • a combination of lowering a vehicle and having low-profile tires
  • the axle geometry being out of specification

Other likely causes of one-sided wear include:

  • Bent, worn out, or damaged front-end parts, such as ball joints, tie rods, springs, and suspension bushings
  • Carrying heavy load frequently
  • Insufficient tire-rotation intervals
  • ban
    Incorrect toe setting
  • ban
    In rare cases, some performance cars may be predisposed to developing one-sided wear prematurely due to the camber angle

What are the risks?

  • Decreased steering response
  • Reduced tire lifespan

What do you have to do?

Usually, correcting any deviation and aligning the wheel correctly is all that’s needed to halt one-sided wear.

You may need to check out the front-end parts if the wear persists after proper wheel alignment.

Tread-wear indicators

How does it appear?

Earlier on in the tire depth section, we discussed using the penny test to find out when it’s necessary to replace a worn grooved tire.

Sometimes, you may not need the penny test. As grooved tires often have tread wear indicators or wear bars sitting in the groove between tread blocks or ribs. And yes, the height of each indicator is 2/32-inch, in accordance with the minimum tread depth requirement.

tread wear indicators

Image: https://www.salvobrothersauto.com/carrepairserviceblog/tires-keep-them-alive-longer/2/27/2017

When the tires are new, these indicators or bars are barely visible. However, as the tread blocks or patterns wear off, they reduce in height until they become flush with the indicators. And the indicators become markedly visible.

What do you have to do?

Replace the tire.

In fact, some experts recommend that you replace the tire before the tread block become flush with the indicators. This is because you’d begin to experience significant performance decline in rainy and snowy conditions, when the tread pattern depth hits between 4/32 inch and 6/32 inch.

Flat spots

a big flat spot on one of the front tires

Photo: https://www.northamericanmotoring.com/forums/tires-wheels-and-brakes/263966-what-causes-a-flat-spot-in-a-tire-like-this.html

What else is it called?

‘Flat spot’ wear, brake skid wear, sometimes called uneven wear.

How does it appear?

Unlike the erstwhile types where wear is continuous, flat spot wear only affects a single spot on the tire. Thus, the tire will predominantly have a normal tread pattern with conspicuous smooth spot(s).

What are the likely causes?

  • When brakes lock up. This typically happens when you slam hard on the brake in an emergency and skid. In cars without an ABS (antilock or antiskid braking system), such heavy breaking will lock up the tires, which can lead to a flat spot
  • Parking a car for extended periods. This is because the car’s weight deforms the tread patch that is in contact with the ground. However, a flat spot being caused by a parked car isn’t a dead cert
    That said, a few factors increase the likelihood of protracted parking resulting in a flat spot
    Bias-ply tires are more susceptible to developing flat spot wear if left to sit for too long. And the susceptibility increases if it sits in any kind of corrosive liquid, say antifreeze or gasoline

What do you have to do?

Check on your brakes to make certain they’re functioning correctly.

Feathering

What else is it called?

Feather(ed) wear.

How does it appear?

You’d observe that a feathered tread block or rib is shaped like a ramp or feather. Feathered wear has a directional wear pattern that goes sideways or from side to side across the tire.

The lower end (edge or side) of the ramp (feathered tread rib) is rounded, while the higher end is sharp. Sometimes, you may be able to spot feather wear visually. However, a reliable way to diagnose feathering is to run your hands across the tread ribs.

What are the likely causes?

  • Incorrect toe setting
  • Damaged or worn suspension bushing. This is the culprit when the toe alignment is correct. A worn suspension bushing would make the wheel’s alignment to shift while you drive
  • ban
    Damaged or worn ball joints and wheel bearings
  • ban
    Sometimes, it may be all down to good ol’ high-speed cornering

What do you have to do?

In most cases, correcting the misalignment (out-of-spec alignment) should do it. However, when an incorrect toe setting isn’t the reason for the feathering, then you should check and replace the damaged suspension, ball joints, and/or wheel bearings.

If high-speed cornering is the cause, dialing it down with aggressive driving—taking it slowly at corners—is the ideal step to take. The alternative is to invest in performance tires outfitted with stiffer sidewalls. These tires can take the abuse from aggressive driving much better than vanilla tires.

Heel-toe wear

heel toe wear

Credit: http://www.bimmerfest.com/forums/showthread.php?t=319624

How does it appear?

Put simply, heel-toe is feathering with ramps running from front to back (rather than side to side). A tread block with heel toe wear would have a smooth leading edge and a sharp trailing edge.

What are the likely causes?

  • Infrequent or improper tire rotation
  • Misaligned, damaged, or worn ball joint, suspension bushings and/or wheel bearings

What do you have to do?

  • Follow your car tire’s maintenance or rotation schedule
  • Check and replace damaged ball joint, suspension bushings, or wheel bearings

Cupping

tire wear cupping

Photo Source: http://forums.vwvortex.com/showthread.php?7164470-This-rear-tire-cupping-is-ridiculous&p=87638474

What else is it called?

Cupped wear, scalloping, scuffing, scalloped edges (or dips).

How does it appear?

Cupping looks like a series of alternating elevations (hills) and depressions (valleys—they appear as bald spots).

What are the likely causes?

  • Faulty shock absorbers. Shocks or dampers have a simple function. They keep your tires in contact with the road. And prevent continuous bouncing by controlling the movement of springs and suspensions
    When they become bad (damaged, bent, or worn), they become ineffective at this important task. And cupped wear sets in
    Although shock absorbers are the usual culprits, any of the several auto parts that connect the wheel to the rest of the car, when worn out or damaged, may be the cause. They include other parts in the suspension assembly, wheel bearing, bushings, ball joint, etc
  • Unbalanced wheel or tires. The severity of cupping caused by a wheel that is out of balance pales in comparison to scalloping caused by a failed shock absorber.
    The scallops are usually fewer and farther between
  • ban
    Infrequent or inconsistent tire rotation

What do you have to do?

  • The first port of call is to check out and replace the shock absorber if it is worn or damaged
    But don’t forget to inspect the entire suspension assembly and other connecting parts for evidence of wear or damage. You’d prolly need to visit an auto repair shop for this
  • Ditto for the wheels if they’re unbalanced

The bottom line is that cupping is hardly ever a sign of normal wear. And its presence alone denotes a substantial safety risk. Thus, you should have it looked at ASAP and not put it off until a later time (procrastinate).

Diagonal swipe

How does it appear?

It is essentially cupping or scalloping in a diagonal pattern.

What are the likely causes?

  • Incorrect toe setting. Often affects the rear tires of a FWD (front wheel drive) car
  • Infrequent tire rotation
  • ban
    Carrying heavy load frequently in the cargo area or trunk. Sometimes, this has an impact (changing the geometry) on the suspension, resulting in diagonal swipe

What do you have to do?

Deal with the causative factors.

If the toe setting is off, have it corrected. If it’s caused by insufficient tire rotation intervals, stick to the rotation schedule religiously going forward.

Cracking and bulging

cracking and bulging

Photo: http://www.ricksautoservice.org/

How does it appear?

It’s hard to miss this one.

Cracking, well, appear as cracks.

Bulging would appear as a pimple in the tire. You’d typically find it in the tire’s sidewall.

What are the likely causes?

Both often result from the tire taking an impact. It could be from hitting a curb, debris, or pothole. However, insufficient (under-) or excessive (over-) inflation of the tires compound the risk of damage.

Cracking

  • If the cracks are large, appear in the sidewall, and run along the rim; they are caused by impacts and chronic underinflation may have played a role
  • If the cracks are small, numerous, and appear in the sidewall or tread blocks; it’s all down to age and exposure to the elements

Bulging

Bulging is the indirect consequence of an impact. Unlike cracking, it doesn’t become visible until weeks or months after the impact. It occurs due to internal damage caused by the impact.

What do you have to do?

Replace the affected tire.

Wrapping Up

Beyond the comfort, better handling, and smooth driving that intact tires help guarantee; they are crucial to safety.

Therefore, it is important that you adhere to your tire maintenance routine. This include:

  • keeping the pressure at the recommended level
  • having each tire checked out regularly
  • rotating them according to schedule, etc

When you do identify a wear, take precautionary measures to know exactly what type of wear you’re dealing with. If you aren’t quite certain of the type, visit your preferred auto shop.

And more importantly, seek to get to the root cause of the wear and resolve it in a timely fashion. Doubly so, if the only option available is to replace the tire: as is the case with tread indicator wear or cracking.

Steven K. Galloway