Can a sidewall be repaired?

Why can't a sidewall be repaired?

The sidewall flexes with every turn of the wheel and holds up the weight of the car. Tire industry repair rules allow repairs in the tread area only.

The tread is thick and backed by steel belts. A small hole there can be filled and sealed. The sidewall is thinner, has no belts, and bends all the time. A plug or patch there keeps moving with the rubber, so it can't hold the way a tread repair does.

The U.S. Tire Manufacturers Association (USTMA) limits repairs to the tread area. Its repair procedure also says never to repair damage that reaches the shoulder or belt edge. The sidewall sits beyond the shoulder, so it is out too.

Where does the tread end and the shoulder start?

The shoulder is the rounded edge between the flat tread and the sidewall. If a hole touches that zone, or nobody can tell where it is, the tire comes out of service.

• Tread: the flat band with grooves that touches the road.
• Shoulder: where the tread curves down at the edge.
• Sidewall: the smooth side with the size and maker's writing.

A nail that sits in the outer groove can be a hard call. USTMA's rule is simple: if there is any doubt that the damage reaches the shoulder, the tire must be taken out of service.

What does a bulge in the sidewall mean?

A bulge or bubble usually means the cords inside the tire are broken, often after a hard pothole or curb hit. Air pushes the rubber out through the weak spot, and the tire can fail.

Bulges often appear a day or two after the hit, not right at the moment. Run your hand along the sidewall, or look at it from the side in good light. A smooth wave or lump that wasn't there before is a warning sign.

• A bulge can't shrink back or be repaired.
• Don't add extra air to "fix" it.
• Replace the tire, even if it holds air.

A tire that fails while driving is a blowout. Our tire blowout guide explains what to do if that happens.

Can you drive on a damaged sidewall to a shop?

Only as far as you must, slowly, and not on the interstate. A safer plan is to put the spare on or have a new tire fitted where the car is.

Speed and heat put the most stress on a weak sidewall. A short, slow trip on surface streets is a lower risk than highway driving. If the tire is also losing air, stop and use the spare.

Not sure the spare is good? Read how long you can drive on a spare. No spare at all? See what to do with no spare.

What about sidewall plug kits and patches?

Some kits and videos show plugging a sidewall, but no tire industry rule allows it. A sidewall plug hides the damage instead of fixing it.

The same goes for sealant from a can. It may stop a leak for a while, but the cut or broken cords are still there. A shop that sees a sidewall plug will usually refuse to work on that tire.

What does a sidewall scuff or crack mean?

It depends on how deep it goes. A light scuff from a curb is often only cosmetic, but a cut that shows cords or fabric means the tire must be replaced.

• Light scuff, no cut: watch it and check the pressure.
• Cut you can catch a fingernail in: have it looked at.
• Cords, threads or wire showing: replace the tire.
• Many small cracks: often a sign of age. Have the tire checked.

Did the hit damage the wheel too?

It can. A pothole or curb strong enough to break the sidewall cords can also bend the rim, so watch for shaking or a tire that keeps losing air after it is replaced.

• Look at the rim edge for dents or chips.
• Feel for a new shake in the steering wheel.
• Notice if the car pulls to one side.
• Check the new tire's pressure again after a few days.

A bent wheel is a job for a wheel or alignment shop. We tell you if we see damage to the rim when we look at the tire.

Can a tire with sidewall damage be kept as a spare?

No. A spare has to be ready for a real emergency, and a tire with a cut or bulge in the sidewall could fail just when you need it.

Do you replace one tire or two?

It depends on the tread on the other tire on the same axle. All-wheel-drive cars may need all tires within a small tread difference, so check the owner's manual.

A new tire next to a worn one can make the car pull or handle unevenly. Matching the size and model on one axle is the usual goal. We check what is available in your size before we quote, and tell you if a second tire makes sense.

How do you read the size on the sidewall?

The size is the code that looks like 225/65R17, printed on the sidewall itself. Take a photo of it before anything else, because a new tire has to match it.

• 225: the tire's width in millimeters.
• 65: how tall the sidewall is, in percent of the width.
• R: radial construction, which almost every car tire uses.
• 17: the wheel diameter in inches.

After the size you often see a load number and a speed letter, such as 102H. The new tire should match or exceed those. The tire's age is in the DOT code: the last four digits give the week and year it was made. USTMA explains how to read that date code.

If the damage is on the outer sidewall, the size may be printed on the inner side too. Your driver's door sticker also lists the original size for your car.

What should you tell us before we come?

The car, the tire size, where the damage is and where the car is parked. A photo of the damaged sidewall lets us confirm it can't be repaired before anyone drives out.

• Is the tire still holding air, or is it flat?
• Do you have a good spare, and its lock key if needed?
• Is the car in a lot, a driveway or at the roadside?

How can you lower the risk next time?

Keep the pressure right and give potholes and curbs room. USTMA advises checking tire pressure once a month, even if your car has a pressure warning light.

• Check pressure monthly, using the number on the driver's door sticker.
• Slow down for potholes, and don't brake hard on top of them.
• Park a little away from tall curbs.
• Look at the sidewalls when you check the pressure.

What does Tire Amigo do about a sidewall?

We don't repair sidewalls, because they can't be safely repaired. A tire tech we work with puts your good spare on, or fits a new tire in your size where the car is parked.

See mobile tire replacement and roadside tire change. You get the all-in price by text before anyone drives out.

When to contact us: Bulge, cut or hole in the sidewall? Send us your details with the tire size from that same sidewall and where the car is.