Straight answer
Should this tire be repaired or replaced?
Not every flat means a new tire, and not every repairable-looking puncture actually is. Three things decide it: where the damage is, how much tread is left, and how old the tire is. Any one of them can rule out a repair on its own.
Usually repairable
- A puncture in the tread area — the flat part that contacts the road
- A hole no bigger than 1/4 inch (6 mm) across
- Damage that has not already been repaired in the same spot
- A tire that was not driven on while flat
- Tread still above 2/32 inch
Needs replacing
- Any puncture or cut in the sidewall or the shoulder
- A hole larger than 1/4 inch, or a slash rather than a puncture
- A tire driven flat or badly under-inflated — the inner liner is chewed up
- Overlapping or repeated repairs in the same area
- Tread at or below 2/32 inch, or visible cords, bulges or dry cracking
Why sidewalls cannot be repaired
The tread sits on top of steel belts and is thick enough to hold a patch. The sidewall flexes on every single rotation and has no belt package behind it, so a plug or patch there works loose and lets go — often at speed. No reputable shop will repair one, and the tire industry's own standards say the same. If the damage is in the sidewall or in the shoulder where the tread curves down, the tire is finished, however new it looks.
What a proper repair actually is
A correct repair means dismounting the tire from the wheel, inspecting the inside for hidden damage, and installing a combination patch-plug from the inside. The plug fills the hole and the patch seals the liner. A string plug jammed in from the outside without removing the tire is a roadside get-home measure, not a permanent fix — it does not seal the liner and it does not let anyone check the inside for damage.
Measuring tread with a penny
Put a penny into the tread groove with Lincoln head down. If you can see the top of his head, you are at or below 2/32 inch and the tire is legally worn out in most states — replace it. A quarter is the more useful test: if you can see the top of Washington's head, you are near 4/32 inch, which is where wet-weather grip starts falling off badly. Check the inner and outer edges as well as the middle; uneven wear across the tread usually means an alignment or suspension problem, not just a worn tire.
Age matters even with good tread
Rubber hardens and cracks with age whether the tire is driven or not. The DOT code on the sidewall ends in four digits — the week and year it was built, so 3222 means the 32nd week of 2022. Many manufacturers recommend replacing at six years and most set ten years as an absolute limit regardless of tread depth. A spare that has never touched the road is still aging on the carrier.
What we do when you bring one in
We take the wheel off, dismount the tire, and look at the inside — which is the only way to know whether it has been run flat or has hidden liner damage. Then we tell you which of the two lists above it lands in. If it is repairable we repair it. If it is not, we will show you why rather than just telling you.
Straight answers
Common questions
Can a tire with a nail in it be repaired?
Usually yes, if the nail is in the tread area, the hole is under 1/4 inch, and the tire has not been driven on flat. If the nail is in the sidewall or shoulder, the tire has to be replaced no matter how new it is.
Is a plug or a patch better for a flat tire?
Neither on its own. The correct repair is a combination patch-plug installed from inside the tire after it has been dismounted and inspected. An outside-only string plug is a temporary measure to get you home, not a permanent repair.
How do I know if my tires are too worn?
Put a penny in the tread groove with Lincoln head down. If the top of his head is visible, the tread is at or below 2/32 inch and the tire needs replacing. Check the inside and outside edges too, not just the centre.
How old is too old for a tire?
The last four digits of the DOT code on the sidewall give the week and year of manufacture. Many manufacturers advise replacing at six years, and ten years is a common hard limit even if the tread looks fine — rubber ages whether or not the tire is used.
Do I have to replace all four tires at once?
Not always, but tires should be replaced in pairs on the same axle so grip is even side to side. All-wheel-drive vehicles are stricter — many require all four to be within a small tread-depth difference to avoid drivetrain damage. Tell us what you drive and we will tell you what it needs.
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