Not every mark on a tyre means a new one is needed, but some kinds of damage are an immediate stop. The useful way to think about it is in three groups: replace now, monitor, and possibly repairable.
Replace now
Some damage compromises the structure of the tyre, and structure is what keeps it from failing at speed. Replace the tyre straight away for any of these:
- A bulge of any size (there is no safe bulge)
- Exposed cord or ply anywhere on the tyre
- A deep cut that has reached the cords
- Any cut, puncture or bulge in the sidewall
- Tread separation: the tread lifting from the casing
- Deep, widespread cracking that reaches the cords
Each of these means the tyre can blow out without warning. None of them is a wait-and-see situation, and several are also illegal to drive on.
Monitor
At the other end are marks that are not, in themselves, dangerous:
- Fine surface crazing with no cords showing
- A light kerb scuff that has not cut into the rubber
These can be watched rather than replaced. The sensible habit is a weekly look to check nothing is progressing, cracks deepening, a scuff turning into a cut, or any sign of a bulge forming. If it changes, it moves into the replace-now group.
Possibly repairable
Between the two sits a narrow band of damage that can sometimes be fixed: a puncture or small cut in the central tread area that has not exposed the cords. Whether a particular tyre qualifies depends on where the damage is and how big it is, and that is governed by a proper repair standard, a subject in its own right. Sidewall and shoulder damage never falls into this group.
If you spot damage away from home
Finding a problem on a driveway is one thing; finding it on a journey is another. With a bulge, exposed cord or any sidewall injury, the safest move is to avoid speed, drive slowly and directly to a fitting centre, or have a replacement fitted where the car stands by a mobile service like Tyres.co.uk. A tyre in that condition is at its most likely to fail under motorway speed and load.
When there is any doubt, the answer is to have it inspected. A fitter can take the tyre off the rim and look inside, and the cost of doing so is nothing against the cost, and danger, of a blowout. Damage is one area where caution is always the cheaper option.
Describe the problem without testing it on the road
Note the affected wheel, warning lights, any impact and whether the vehicle is in a safe place. Photographs taken away from traffic can help a recovery service plan the visit. Do not drive around to see whether the vibration disappears, and do not inflate a visibly damaged tyre as an experiment.
If you are exposed to traffic, getting help takes priority over inspecting the wheel. Follow the road's breakdown procedure. On a motorway, do not attempt tyre repairs yourself. The fact that a garage is nearby does not make a damaged tyre safe for the journey.
Common questions
When does tyre damage mean I must replace the tyre?+
Replace immediately for any bulge, any exposed cord, a deep cut that reaches the cords, any sidewall cut or puncture, tread separation, or deep widespread cracking. All of these compromise the structure and risk a blowout.
What tyre damage can I just keep an eye on?+
Light cosmetic marks, fine surface crazing with no cords showing, or a shallow kerb scuff that hasn't cut into the rubber. These can be monitored weekly for any sign of getting worse, rather than replaced straight away.
Can I drive home on a damaged tyre?+
It depends on the damage. With a bulge, exposed cord or sidewall injury, avoid driving at speed, go slowly and directly to a fitter or use the spare. When in doubt, have it inspected rather than risk a failure at speed.
Is it worth getting a damaged tyre inspected?+
Yes. A professional can take the tyre off the rim and check inside, and the cost of an inspection is trivial next to the cost and danger of a sidewall blowout at motorway speed. When unsure, get it looked at.