When to Replace Car Tyres: Tread, Age & Warning Signs

Learn exactly when to replace car tyres using tread depth, age, wear patterns and damage checks, plus realistic costs and a quick DIY inspection.

Your tyres are the only part of the car that actually touches the road, so knowing when to replace car tyres is one of the most important safety decisions you make as a driver. Grip, braking distance, steering response and aquaplaning resistance all depend on healthy rubber. This guide walks through the four things that really matter — tread depth, age, wear patterns and physical damage — with clear thresholds, a DIY inspection you can do in ten minutes, and realistic replacement costs.

The four signs it's time for new tyres

Most tyres are retired for one of four reasons. You should replace a tyre when any single one of these is true — they are not a checklist where you need all four.

1. Tread depth has reached the legal or practical limit.
2. The tyre is too old, even if the tread still looks deep.
3. The wear is uneven, signalling a mechanical fault and a compromised contact patch.
4. There is structural damage — a bulge, deep cut, or sidewall crack.

Let's take each one in turn, because the details are where drivers get caught out.

1. Tread depth: the number that matters most

Tread channels the water out from under the tyre. As they wear down, wet grip falls off a cliff long before the tread disappears completely. The legal minimum in most regions is 1.6 mm across the central three-quarters of the tyre, but braking tests consistently show that stopping distances in the wet grow dramatically once you drop below about 3 mm.

How to check tread depth yourself

You do not need special tools, though a cheap depth gauge helps.

1. Look for the tread wear indicators — small raised bars moulded into the bottom of the grooves. When the tread is flush with these bars, the tyre is at 1.6 mm and finished.
2. No gauge? Use a coin with a known rim width and insert it into the main groove. If the outer band of the coin stays hidden, you have a safe margin; if it's fully visible, the tread is low.
3. Check in several places — inner edge, centre and outer edge — and on both sides of the car. Uneven readings are a warning in themselves (see section 3).

Measure across at least three points around the circumference too, because a tyre can wear unevenly front-to-back as well as side-to-side.

2. Tyre age: rubber has a shelf life

Rubber hardens and cracks with age regardless of mileage. A tyre with plenty of tread can still be unsafe if it has been baking in the sun on a rarely used car or a caravan for years. Most manufacturers advise replacing tyres that are six years old, and treating ten years as an absolute maximum even for a spare.

You can read the exact manufacture date from the DOT code on the sidewall. Look for a four-digit number, usually inside an oval: the first two digits are the week and the last two are the year. So 2621 means the 26th week of 2021.

• Under 6 years: age is not a concern on its own.
• 6–10 years: inspect closely each year for cracking and hardening.
• Over 10 years: replace regardless of tread.

Hairline cracks in the tread grooves or sidewall — often called weather-checking or dry rot — mean the rubber has degraded and the tyre should come off even if it looks fine from a distance.

3. Uneven wear patterns and what they tell you

How a tyre wears is a free diagnosis of your car's mechanical health. Replacing the tyre without fixing the cause just wastes money, because the new one will wear the same way.

Under- and over-inflation are the easiest to prevent. Check pressures cold, at least monthly, against the figure on the driver's door jamb or inside the fuel flap — not the maximum stamped on the tyre. Correct pressures alone can add thousands of kilometres of tyre life and cut fuel use. Our free car tools include a tyre pressure reference you can bookmark.

If a wheel-alignment or suspension problem is behind the wear, that is safety-critical work best handed to a qualified mechanic rather than guessed at.

4. Damage that ends a tyre immediately

Some faults mean a tyre must be replaced no matter how much tread is left:

• Sidewall bulge or blister — the internal cords have broken and the tyre can blow out without warning.
• Cuts or cracks deep enough to expose the fabric or steel belts.
• A puncture in the sidewall or shoulder — only punctures in the central tread area, under a certain size, can be safely repaired.
• Persistent vibration at speed after a fresh balance, which can indicate a separated belt inside the tyre.

A repairable tread puncture typically costs $20–$45. Anything in the sidewall is not repairable and means a new tyre. If you feel a new steering-wheel wobble or the car pulls to one side, don't ignore it — and if a dashboard warning light appears alongside it, you can decode the fault with our OBD-II code lookup before you visit a workshop.

What replacing tyres actually costs

Prices vary hugely with size and brand, but these ranges are realistic per tyre, fitted and balanced:

Buy in pairs at minimum, and always fit the newer, deeper tyres to the rear axle regardless of whether the car is front- or rear-wheel drive. Rear grip is what keeps the car stable and predictable in a wet corner; a car that loses the rear is far harder to control than one that pushes wide at the front.

A quick 10-minute tyre health check

Run through this once a month and before any long trip:

1. Pressures cold, all four plus the spare, set to the door-jamb figure.
2. Tread depth at inner, centre and outer bands on each tyre.
3. Tread wear indicators — are any flush with the tread?
4. Sidewalls for bulges, cuts and cracking.
5. DOT date code — note the age of each tyre.
6. Wear pattern — is it even side to side?
7. Objects — pick out embedded stones, screws or nails.

If you want to go deeper on stopping performance, pair this with a look at your brakes in our guide on how to know when brake pads need replacing.

Frequently asked questions

Should I replace all four tyres at the same time?

Ideally on all-wheel-drive cars, yes, because a mismatched rolling diameter can strain the drivetrain. On two-wheel-drive cars you can replace in pairs, but always match the pair across the same axle and put the deeper tread on the rear. Mixing very different tread depths front to rear changes how the car handles at the limit.

How long do car tyres normally last?

Most tyres cover roughly 40,000–80,000 km depending on the compound, your driving style and how well pressures and alignment are maintained. Performance and soft compounds wear faster. Remember that age can retire a tyre before mileage does, so check the DOT date as well as the tread.

Is it safe to drive on the spare for a long time?

A full-size matching spare is fine indefinitely if it's in good condition and correctly inflated. A compact "space-saver" spare is a get-you-home item only: keep below the speed printed on it (usually around 80 km/h) and replace the damaged tyre as soon as possible, as space-savers offer far less grip and no long-term durability.