What the sidewall does
The sidewall is the side of the tire between the tread and the wheel. It's thin compared with the tread, it carries much of the car's weight, and it bends with every turn of the wheel. Cords run through it that give the tire its shape and strength.
That's the reason a repair doesn't work there. A patch or plug needs a stable spot to bond to, and the sidewall never stops moving. A repair there can work loose, and a failed sidewall at speed means a blowout.
That's also why tire shops treat sidewall damage differently from a puncture, and why they aren't just being picky. A tread puncture is a small hole in a thick part of the tire that stays put. A sidewall cut is a wound in a part that never gets to rest.
Signs the sidewall is damaged
Run a hand along the inside and outside of each tire when you check it. Look and feel for:
- A bulge or bubble. This usually means the cords inside have broken and only the outer rubber is holding the air.
- A cut or gouge deep enough to show fabric or cord.
- Cracking, or deep scrapes from rubbing a curb.
- A tire that keeps losing air with no puncture you can find in the tread.
After a hard hit
Hitting a pothole, a curb or road debris can damage a sidewall without flattening the tire. The tire may look fine and then fail days later. If you hit something hard, look at the sides of the tire afterward, and ask a tire shop to look if anything seems off, including a new vibration or a car that pulls to one side.
A bulge is the one to take seriously. A tire with a bulge shouldn't be driven on, even slowly, and shouldn't wait for the weekend.
When a damaged sidewall does fail, it fails suddenly, and usually when the tire is hot and loaded, with the weak spot flexing on every rotation. A summer drive on a DFW freeway is exactly that.
What to do about it
The fix is a replacement tire. If the tire is flat, put the spare on and get a new tire as soon as you can. If you have no spare, TRA supplies a tire and installs it on site. Tire replacement is from $129, plus a $19 dispatch fee charged once per job. Tire availability varies by size, so give dispatch the size from the tire's sidewall or the driver's door jamb sticker, and dispatch confirms a tire is available before a driver is sent.
If your car is all-wheel drive, mention it. Some of them need all four tires to have about the same wear, and a mismatched new tire can matter.
Common questions
Not reliably. A cut that goes through the outer rubber can be the start of a failure, and there's no way to repair it safely. Have it looked at by a tire shop before you drive any real distance.
No. Those are meant for small punctures in the tread. Sidewall damage can't be sealed in a way you should trust.
Usually not. One tire is the normal replacement. All-wheel-drive vehicles can be an exception, so check the manual or ask the tire shop.
It's a reason not to drive on the tire. A bulge means the cords inside have given way, so the tire could fail at any moment. Put the spare on, or call for help, before you move the car any distance.