You don't always need four new tyres. You can usually replace a single damaged tyre if the others still have plenty of tread. The key is to keep grip balanced, so a new tyre is best matched to its partner on the same axle, and all-wheel-drive cars are a special case that often need all four. Here's how to decide.
When one tyre is fine
If one tyre is damaged beyond repair but the other three have plenty of tread and are in good condition, replacing just the one is usually fine and the most economical choice. There's no rule that says you must replace all four because one failed. The main thing is that the new tyre is a sensible match for the others, see below.
When to do a pair
It's good practice to keep both tyres on an axle matched, so if the partner tyre is also worn or noticeably different, replacing the pair keeps grip balanced left-to-right. When you fit just two, the new pair is generally best on the rear axle: deeper tread there clears water better and keeps the back of the car stable in the wet (TyreSafe), see replacing tyres in pairs for why. This is about safe, predictable handling.
All-wheel-drive is different
All-wheel-drive and many four-wheel-drive cars are the exception. Mismatched tyre diameters (which differ with tread depth) can strain the drivetrain, so many makers require all four tyres replaced together, or kept within a small tread difference. If you have an AWD car, check the handbook before replacing just one, as getting this wrong can be an expensive mistake.
Matching tread and type
Whatever you replace, match the size and ratings, and ideally the same or a similar tyre, at least across the axle. Mixing very different tyres, or a summer and a winter tyre, on the same axle unbalances grip. If money is tight, a sensible single replacement that matches well beats stretching to a cheap mismatched set, see budget vs premium.
One, two or four: a quick decision table
Most cases fall into one of a handful of situations, and the sensible answer for each is fairly settled. Use this as a starting point, then check the handbook if the car is all-wheel drive.
| Situation | Usual answer | Why |
|---|---|---|
| One tyre damaged, other three nearly new and matching | Replace one, same make and pattern if possible | Tread difference across the axle is small, grip stays balanced |
| One tyre damaged, its axle partner half worn or more | Replace the pair on that axle | Keeps left and right matched; the worn partner was due soon anyway |
| One tyre damaged, a different make or pattern on the partner | Replace the pair | Mixed patterns on one axle behave differently in the wet |
| Fronts worn, rears good (typical front-wheel drive) | Replace two, fit the new pair to the rear, move the rears forward | Deeper tread at the back resists aquaplaning and oversteer |
| All four within a millimetre or two of the limit | Replace all four | Replacing one at a time here means separate jobs within months for tyres that are all due |
| All-wheel drive or 4x4, any of the above | Check the handbook; often all four | Diameter mismatch loads the centre differential or transfer case |
If your car has a full-size spare of the same specification, it can sometimes serve as the fourth tyre in a pair replacement. That saves buying a tyre you already own, provided the spare is not too old.
How much tread difference is too much?
UK law sets no rule on tread difference between tyres, only a minimum of 1.6mm across the central three-quarters of each one, but a mismatch of several millimetres on one axle is worth avoiding. The legal position is on GOV.UK. The practical guidance below is what fitters work to.
A new car tyre typically starts with around 8mm of tread. If its axle partner is down to 3mm, one side of the car clears water far better than the other under braking, which is exactly when you want the two sides behaving the same.
As a rule of thumb, aim to keep the two tyres on an axle within a couple of millimetres of each other.
Across axles the tolerance is looser on a two-wheel-drive car. A deeper pair at the rear and a shallower pair at the front is the normal and preferred state.
All-wheel drive is different. Handbooks for many AWD cars limit the tread or circumference difference across all four tyres to a small figure, and some require all four to be replaced together once any one is beyond it.
The reason is simple: a slightly smaller tyre turns faster, and the drivetrain has to absorb that difference continuously. Check the figure for your car before buying.
When your exact tyre is discontinued
If the matching tyre is no longer made, match the specification and the type first and the brand second. Tyre ranges are refreshed every few years, so a four-year-old car can easily be running a pattern that is now out of production.
Work through it in this order:
- Size, load index and speed rating must match what the car requires, see load and speed ratings. Never go below.
- Season and category: summer with summer, all-season with all-season. Do not mix a winter tyre with a summer tyre on one axle.
- Pattern type: pair a directional with a directional, an asymmetric with an asymmetric, see directional vs asymmetric tyres.
- Brand and successor range: most makers have a direct replacement (for example a newer generation of the same line), which will be the closest match in feel.
- Label grades: if you are choosing between candidates, pick the one whose wet-grip grade is closest to, or better than, the tyre it is partnering.
If none of that produces a sensible match, replacing the pair with something you can buy again in future is usually the better spend.
Check whether it can be repaired first
Some tyres that look like write-offs are repairable, and a repair costs a fraction of a replacement, so rule it out before buying anything. The British Standard for tyre repair, BS AU 159, sets the limits a reputable repairer works to.
In short, a puncture can normally be repaired if the hole is in the central three-quarters of the tread, no more than 6mm across, and the tyre has not been driven on flat or badly under-inflated. Sidewall and shoulder damage, larger holes, and tyres with internal damage from running flat are replacements.
Our guide to whether a puncture can be repaired covers the detail, and mobile puncture repair is done at your location.
Two situations are worth flagging. For run-flats, the tyre maker's policy decides whether a repair is allowed, and one that has been driven deflated is usually replaced. And a tyre that has been plugged from the outside with a string repair is a temporary fix at best, because the inside has not been inspected.
If the tyre is not repairable, the repair inspection has still done something useful: the fitter has now seen all four tyres and can tell you honestly whether one, two or four is the right call.
We'll advise honestly
We'll tell you honestly whether one, two or four tyres make sense for your car, including AWD, and fit them at home or at work in London and the Home Counties, and further out in the Midlands when the diary allows, from our one base at Brent Cross, NW2. We give you the arrival time when you call. Call 07473 720871 or book online.
