Shoulders & Sidewalls: When to Repair, When to Replace Tires Based on Wear, Tear and Damage

This car tire diagram from Yokohama shows where the tire shoulder begins; it ends where the sidewall begins. 

Many factors go into when to repair or replace your tires. It's not just when the manufacturer suggests it's time.

You also need to look into the tire's structure. More specifically, a tire's shoulders and sidewalls. So, let's dive in and answer some critical questions, like when is it OK to repair a puncture and when do you have to replace a damaged tire?

What Are Sidewalls and Shoulders of a Tire?

Before we give repair and replace advice, let's define what exactly sidewalls and shoulders on tires are.

Tire sidewall definition

The sidewall is the smooth, vertical area on the side of the tire between its bead and the edge of the tread. It's also the section of a tire where you'll find markings with helpful information, such as tire size and type.

Tire shoulder definition

The region where the tread and sidewall meet. This includes the tread blocks closest to the side of the tire and the area transitioning to where tread grooves are still visible.

Source: FAA. Yes, airplanes have tires too, and they have the same anatomical shoulders, treads, and sidewalls.

Tire Sidewall Cracking Chart

Yeah, we've seen it. There is a chart floating around the internet that illustrates when tire cracks are acceptable, suspect and time to replace (rejected). We're not sharing it. Wanna know why? Most drivers (no offense, many on our editorial team are in the same boat) aren't qualified to diagnose cracks in tire sidewalls, even with a comparison chart. 

Here's what we will say:

• Minor sidewall cracks: The only place you should drive is to the nearest garage, where you can replace your tires, if it is safe to do so. Minor sidewall cracks lead to suspect sidewall cracks. 
• Suspect sidewall cracks: The only place you should drive is to the side of the road, where you can change your tire or call a tow truck to safely tow your vehicle to a garage. Suspect sidewall cracks will become dangerous.
• Dangerous sidewall cracks: Do not drive on severely cracked tires. Replace the tire as soon as you can. Dangerously cracked sidewall tires lead to blowouts and, potentially, crashes.     

Is a Tire Shoulder Repairable?

According to the U.S. Tire Manufacturer Association (USTMA), the only area of a tire that can safely be repaired is the center of the tread area. You should not repair a shoulder or sidewall. 

Another thing to remember is that the puncture can be no larger than 1/4 inch in diameter to be safely fixed.

Even if the damage is limited to the tread area, you'll want to have it checked out by a tire professional. Cracks, punctures and other damage need to be checked for severity. It's always better to be safe than sorry.

Are Tire Sidewall Punctures Repairable?

As touched on in the previous section, you want to avoid sidewall puncture repairs. Replace the tire. It's partly because the tire compound is likely composed of steel rings that deliver balance and power, making it nearly impossible to repair.

If the sidewall area is patched, you're taking the risk that your car won't perform correctly. Even worse, a patched sidewall has a more heightened risk of suffering a blowout, which could lead to a serious accident.

So if a nail or foreign object punctures your tire's sidewall, it's time to replace the tire.

How Safe Are Tires That Have Sidewall Cracks?

Cracking occurs in tires through the aging process. It's when rubber and polymer materials break down due to a few reasons, including:

• Age
• Lack of use
• Poor tire care
• Weather

Here are a few preventative maintenance tips to follow to help deter cracking: Ensure your tires are always correctly inflated. Drive on the tire regularly. And finally, park out of sunlight when possible, especially if you live in dry, sunny climates.

You're probably wondering if tires with sidewall cracks are safe and if they can be repaired? Honestly, the answer to both is no.

SHOP NEW TIRES NOW

That's because tires with deep and widespread cracks are beyond their useful age and need to be replaced yesterday. Cracking sidewalls are signs of aging and are dangerous to drive on. They are at severe risk of a blowout, which could lead to a harmful crash.

Can Tire Shoulder Cracks Be Repaired?

As we mentioned earlier, cracks found on tires signify aging. The good news is most tires are expected to last from five to seven years.

But that doesn't mean you should ignore visible cracks. And remember, the only repairable area of a tire is the center of the tread area -- the part that touches the pavement.

Your safest move is to take your vehicle to a tire professional and have them inspected. If the cracks are severe, your tire needs to be replaced. Most likely, the tire has become brittle and isn't safe.