When Should You Replace Your Tyres?
Most drivers replace their tyres when the tread looks low, or worse, when they are already bald. It is a reasonable instinct, sometimes unavoidable in a cost of living crisis, but it is sometimes not the only indicator of the tyres end-of-life.
A tyre can have plenty of tread remaining and still need replacement because of age, structural damage or uneven wear. It can also remain technically legal while delivering substantially less wet-weather grip than it did when new.
There are three separate clocks running on every tyre: tread depth, age and condition. A tyre should be replaced when any one of those clocks runs out, not when all three do.
This guide explains what Australian law requires, what tyre owners should inspect and when replacement becomes the safest option.
Three Clocks, Not One
Every tyre deteriorates in three different ways.
The first is tread depth. The grooves across the tyre help disperse water and maintain contact with the road. This is the most visible form of tyre wear and the one most drivers recognise.
The second is age. Tyre rubber gradually hardens and deteriorates, regardless of how much tread remains. This process continues even when a vehicle is rarely driven.
The third is condition. Kerb strikes, potholes, heat, sunlight, incorrect inflation pressures and mechanical problems can all shorten a tyre’s usable life. Unlike normal treadwear, damage does not necessarily develop gradually. One severe impact may be enough to compromise a tyre’s internal structure.
A tyre needs replacement when any one of these factors makes it unsafe or unroadworthy.
The Legal Tread-Depth Limit in Australia
The minimum legal tread depth for passenger vehicle tyres in Australia is 1.5 millimetres, measured within the principal grooves of the tread.
Once any relevant section of the tyre falls below the legal requirement, the tyre is no longer roadworthy and should be replaced immediately.
However, 1.5 mm should not be treated as a replacement target. It is the legal minimum, not an indication that the tyre will continue to perform as effectively as it did with more tread.
Drivers who wait until their tyres reach the legal limit leave themselves with little margin for uneven wear, unexpected wet weather or a long journey that could wear the tyre further.
Legal Minimum Versus Safe Replacement Point
Tread grooves are designed to move water away from the tyre’s contact patch. As those grooves become shallower, the tyre has less capacity to disperse water.
This can reduce wet-weather grip and increase braking distances well before the tyre reaches the legal limit.
For this reason, many tyre professionals recommend that drivers begin planning for replacement when tread depth approaches 3 mm, particularly where the vehicle regularly travels at highway speeds or in wet conditions.
This is guidance rather than an additional legal requirement. The appropriate replacement point will also depend on the tyre, vehicle, driving conditions and wear pattern.
The practical distinction is simple:
- 1.5 mm is the legal minimum.
- Around 3 mm is a sensible point to start assessing and planning for replacement.
Waiting until a tyre reaches 1.5 mm may be legal, but it does not necessarily provide the safety margin every driver will want.
How to Check Your Tyre Tread
A quick visual inspection can identify obvious wear, but tread depth should be checked in several places across each tyre.
Check the tread wear indicators
Most modern passenger vehicle tyres have raised tread wear indicators moulded into the principal grooves. Their location is often identified by small markings on the tyre’s shoulder.
When the surrounding tread has worn level with an indicator, the tyre has reached approximately 1.5 mm at that point and is due for immediate replacement.
Do not inspect only the centre of the tread. Check the inner and outer sections as well, because alignment, suspension and inflation problems can cause one part of the tyre to wear more quickly than another.
Use a tread-depth gauge
A tread-depth gauge provides an actual measurement in millimetres and is more reliable than estimating tread depth visually.
Measure several points across the tyre and repeat the check at different positions around its circumference. The lowest reading is the one that matters.
Treat coin tests as a rough indication
A coin can provide a quick visual reference, but it is not a precise measurement and should not be relied upon to confirm whether a tyre is roadworthy.
If a tyre appears close to the legal limit, use a tread-depth gauge or have it inspected by a tyre retailer.
The Age Clock
Australia does not impose a single maximum legal age that automatically makes every tyre unroadworthy. However, this does not mean tyre age can be ignored.
Tyre rubber changes over time as it is exposed to heat, sunlight, oxygen and repeated temperature cycles. The compound can harden and lose elasticity, potentially reducing grip even where the tread still appears deep.
Age is particularly important for:
- Low-kilometre vehicles
- Caravans and trailers
- Collector or recreational vehicles
- Vehicles stored outside
- Spare tyres that have rarely or never been used
Industry guidance commonly recommends having tyres professionally inspected each year once they are approximately five years old. Replacement should generally be considered by around seven to ten years from the manufacturing date, regardless of the remaining tread.
These are guidelines rather than Australian legal deadlines. The tyre’s condition, storage environment and manufacturer recommendations should also be considered.
How to find the tyre’s age
The manufacturing date is identified by the final four digits of the tyre identification code moulded into the sidewall.
The first two digits represent the week of manufacture and the final two represent the year. For example, a code ending in 2621 indicates that the tyre was manufactured during the 26th week of 2021.
The date refers to when the tyre was manufactured, not when it was fitted to the vehicle or when the vehicle was purchased.
We cover tyre age and DOT in detail in this article.
The Condition Clock
Some tyres need replacement long before age or tread depth becomes the deciding factor.
Sidewall bulges
A bulge or bubble in the sidewall can indicate damage to the tyre’s internal structure, often following contact with a pothole or kerb.
A tyre with a sidewall bulge should not remain in service. Have it replaced and ask the tyre retailer to inspect the wheel and surrounding components for impact damage.
Cuts and exposed material
Cuts, splits or damage deep enough to expose internal cords require immediate professional attention. The visible opening may represent only part of the damage.
Do not attempt to repair sidewall damage with a temporary puncture product.
Cracking
Fine cracking around the sidewall or within the tread grooves can indicate that the rubber has deteriorated because of age, heat, sunlight or environmental exposure.
The severity matters, so have the tyre professionally inspected rather than assuming that every surface mark is harmless or that every small crack automatically requires replacement.
Uneven treadwear
Uneven wear is more than a tyre replacement issue. It can reveal a problem with the vehicle or its maintenance.
Common patterns include:
- Wear through the centre: May indicate excessive inflation pressure.
- Wear on both shoulders: May indicate insufficient inflation pressure.
- Wear concentrated on one edge: Often associated with wheel alignment or suspension geometry.
- Cupped, patchy or feathered wear: May be related to balance, alignment, suspension or component wear.
Replacing the tyre without correcting the underlying cause can allow the same wear pattern to develop on the new tyre.
If uneven wear is visible, ask the retailer to investigate the cause before or while fitting the replacement tyres.
Do Not Forget the Spare Tyre
The spare is often the oldest and least frequently inspected tyre on the vehicle.
Check its pressure, condition and manufacturing date at the same time as the tyres fitted to the vehicle. Discovering that the spare is flat, cracked or excessively old after a puncture defeats its purpose.
If the vehicle has a temporary space-saver spare, follow the speed and distance restrictions shown on the tyre and in the owner’s manual. A space-saver is intended to help the vehicle reach a safe location or tyre retailer. It is not a permanent replacement for the damaged road tyre.
Some newer vehicles do not include a spare at all. They may instead use a puncture repair kit or run-flat tyres. Owners should understand which system their vehicle carries before an emergency occurs.
What Happens If a Tyre Is Illegal?
Driving with tyres that do not meet roadworthy requirements can result in a fine, defect notice or other enforcement action.
The applicable penalties vary between states and territories and may change over time. Multiple unroadworthy tyres can also result in multiple offences or prevent the vehicle from being driven until the defects are corrected.
Drivers should confirm current penalties with their state or territory road authority rather than relying on older published figures.
The greater concern is the safety risk. A tyre that has worn below the legal limit has reduced tread available to disperse water, increasing the likelihood of losing grip in wet conditions.
There may also be insurance implications if a vehicle involved in an incident is found to have been unroadworthy, depending on the circumstances and the terms of the individual policy.
A Five-Minute Tyre Replacement Check
Inspect your tyres at least once a month and before a long journey. Most reputable tyre retail outlets provide free safety checks on cars, so if you are not sure what to look for, make it a habit to drop in at your local tyre store at least every 3 – 6 months.
Ask the following questions:
- Tread: Are any tread wear indicators level with the surrounding tread? Is any section approaching 1.5 mm?
- Age: How old is each tyre? Has any tyre more than five years old received a recent professional inspection?
- Condition: Are there bulges, cuts, cracks, exposed cords or other visible damage?
- Wear pattern: Is the tread wearing evenly across the full width of the tyre?
- Cause: If wear is uneven, has the vehicle’s inflation pressure, wheel alignment, balance or suspension been checked?
- Spare: Is the spare correctly inflated, in good condition and young enough to be used safely?
When Replacement Becomes Necessary
You should replace a tyre when:
- Its tread reaches the legal minimum
- It has a sidewall bulge or serious structural damage
- Cuts or splits expose internal material
- Age-related deterioration makes continued use unsafe
- Uneven wear leaves part of the tyre below the legal requirement
- A tyre professional determines that it cannot be safely repaired
Replacement is not determined by tread depth alone. A tyre with deep tread can still be unsuitable for use because of age or damage, while a tyre that remains legal may no longer provide the wet-weather performance margin a driver expects.
The safest approach is to monitor all three clocks: tread, age and condition. Whichever one runs out first determines when the tyre needs to be replaced.
Frequently Asked Questions
What is the legal minimum tyre tread depth in Australia?
The minimum legal tread depth for passenger vehicle tyres in Australia is 1.5 mm within the principal tread grooves. If any relevant section falls below this limit, the tyre should be replaced immediately.
Should I wait until my tyres reach 1.5 mm before replacing them?
Not necessarily. The 1.5 mm requirement is a legal minimum, not an ideal replacement target. Wet-weather performance can decline as the tread wears, so it is sensible to begin assessing and planning for replacement when tread depth approaches 3 mm.
How can I tell if my tyre has reached the tread wear indicators?
Tread wear indicators are raised bars positioned inside the tyre’s principal grooves. When the surrounding tread wears level with these bars, the tyre has approximately 1.5 mm of tread remaining at that point.
How often should I inspect my tyres?
Check your tyres at least once a month and before long journeys. Inspect the tread depth, inflation pressure, wear pattern, sidewalls and spare tyre. More frequent checks may be appropriate if the vehicle covers high kilometres or regularly travels on poor roads.
Is the $2 coin test an accurate way to measure tyre tread?
A $2 coin can provide a quick visual indication, but it is not a precise measurement of tread depth. Use a tread-depth gauge or ask a tyre retailer to inspect the tyre if it appears close to the legal limit.
Do tyres need replacing because of age if they still have plenty of tread?
They may. Tyre rubber gradually deteriorates as it is exposed to heat, sunlight, oxygen and temperature changes. Tyres should generally receive annual professional inspections once they are around five years old, with replacement considered by approximately ten years from manufacture.
Can a tyre with legal tread depth still be unsafe?
Yes. A tyre may have sufficient tread but still be unsafe because of a sidewall bulge, deep cut, cracking, exposed internal material, impact damage or age-related deterioration. Tread depth is only one part of assessing tyre condition.
Should the spare tyre be replaced because of age?
Yes, when necessary. Spare tyres deteriorate even when they have never been used. Check the spare’s manufacturing date, pressure and condition regularly, and have an ageing or damaged spare professionally assessed.
