Short answer: No. A bulge or a deep cut in the sidewall means the tyre is damaged and it should be replaced, not repaired. The sidewall flexes all the time and cannot be patched safely. Stop driving on it at speed and have the tyre checked by a workshop as soon as you can.
What is a sidewall bulge?
A bulge is a bump or blister on the side of the tyre. It usually means the internal structure of the tyre has been damaged, often by an impact with a kerb, a pothole or road debris, and air pressure is pushing the weakened area outwards. The tyre can look fine from the tread side, so check the sides too.
Why is it not safe to keep driving?
The sidewall carries load and flexes with every turn of the wheel. Once the structure behind a bulge is weakened, the tyre can fail suddenly, especially at higher speeds or under load. That is why a bulge is treated as a replace-now fault rather than something to monitor.
What about a cut or a scrape in the sidewall?
A light scuff on the rubber surface is different from a cut. A cut that goes deep, shows cords or fabric, or lets air out needs a replacement. If you are not sure how deep it is, have a workshop look at it. Cracks in the rubber from age are also a reason to have the tyre checked.
Can a sidewall be repaired?
No. A puncture in the tread area can often be repaired if it is small, but a damaged sidewall or shoulder cannot be repaired safely, because that part of the tyre flexes constantly. The tyre is replaced instead.
What should you do if you find one?
Check how far you are from a workshop. If the tyre still holds air and you must move the car, drive slowly and gently to a safe place, or to the workshop, and avoid highways. If the tyre is losing air, or the bulge is large, fit the spare or call for help rather than driving on it.
How do you avoid sidewall damage?
Slow down for potholes and road works, avoid hitting kerbs when you park, and keep the tyres at the pressure your car maker specifies, because an under-inflated tyre is more easily damaged by an impact. Look over all four tyres, including the inner sides, every so often, and have the spare checked too.
What the workshop checks
We inspect the whole tyre, not just the damaged spot: the sidewall on both sides, the tread, the tyre age from its date code, and the pressures. If one tyre is damaged by an impact, we also look for wheel or suspension damage, and tell you what we found before anything is replaced.
Common questions
Is a bulge in my tyre sidewall dangerous?
Yes. A bulge means the tyre structure is damaged and the tyre can fail suddenly. It should be replaced as soon as possible and not driven on at speed.
Can a tyre sidewall bulge be repaired?
No. Sidewalls flex all the time and cannot be repaired safely, so a tyre with a bulge or a deep sidewall cut is replaced.
What causes a bulge in the sidewall?
Usually an impact, such as hitting a kerb or a pothole, which damages the internal structure of the tyre. Driving on an under-inflated tyre also makes damage more likely.
Is a small cut in the sidewall safe?
A light surface scuff may be only cosmetic, but a cut that is deep, shows cords or loses air is not safe. If you cannot tell, have a workshop inspect the tyre.
Should I replace one tyre or two?
That depends on the other tyres, such as their tread depth and age. A workshop can check them and advise whether one tyre or a pair makes sense for your car.
