Most Australians don’t know when to replace their car tyres or why tyre tread depth is so important. Here’s how to check that your tyres are ok.

Many drivers don’t check their tyres and rely one the mechanic or when something goes wrong to know that the tyre are not safe. To keep safe, you really need to get into a habit of checking your tyres regularly.

Whether you drive a sports car or SUV, the condition of your tyres is more influential in the way your car grips the road than almost anything else. We’ve all seen those ads on TV talking about how there’s only a hand-heel-amount of rubber (otherwise known as ‘contact patch’) on the road per tyre, so it pays to make sure you’ve got as much ‘meat’ on your tyres as possible.

See, while cars these days are loaded down with sophisticated traction and stability controls, autonomous emergency braking, lane-keeping assist and more, none of it matters a jot if you don’t have any grip left on your tyres.

Checking your tyres regularly

Check the air pressure in your car’s tyres at least once a month (or before a big trip) and preferably with an air pressure gauge, and check the spare too. You can buy a cheap one for around $20 and keep it in your car.

The manufacturer’s air pressure specifications are usually on a placard on the inside edge of the driver’s door or along a door jamb. Improper wheel alignment can also cause your tyres to wear unevenly and prematurely. You should be able to feel a slight tugging through the steering wheel if your car’s wheels are out of alignment.

Some recommend using coins, but it’s cheaper and easier just go to your local automotive retail store and buy a tyre tread depth gauge. A basic gauge will cost you less than $10. If you do use a gauge, don’t just check one of your tyres, check them all, and don’t just check the tyres in one spot, check them in several areas.

If you own a trailer and use it regularly, then it pays to regularly check the tyres on your trailer. More than just the depth of the tread you should also keep an eye on the age of your trailer’s tyres. These things get a lot less use or attention than the tyres on your car and age is not a tyre’s friend. So, look for signs of splitting, etc as the tyre becomes harder. And, remember, if in doubt, get it checked out.

What causes tyre wear?

Beyond just general use, there are a couple of things that can lead to premature tyre wear, like improper inflation of your vehicle’s tyres. If the tyre is under- or overinflated than it’s not able to do, properly, the job it was designed to do and so can end wearing unevenly due to improper stress, causing it to wear unevenly or too quickly.

What’s the legal minimum tread depth?

The average tyre has around 8mm of tread depth when brand new. At 3mm it’s recommended you replace your tyres and at the minimum tread depth of 1.5mm (across around three-quarters of the tyre’s surface) you’re tyres are worn out. Continuing to drive on tyres with only 1.6mm of tread or less can lead to a hefty fine of more than $200 and several demerit points, depending on the State or Territory you live in. More than this, you’re endangering your own life and the lives of those around you.

With each loss of tread depth your tyre’s functionality is being reduced, meaning its ability to shed water is reduced, its grip is reduced and thus braking distances increase. Travelling at around 80km/h on brand new tyres on a wet road will see most cars pull up in around 100m; halve the tread and this stopping distance blows out to around 120m; wear your tyres down to 1.5mm and your stopping distance will be nudging closer to 140m.

What’s the point of tyre tread?

Beyond helping your tyre grip the road, the grooves on your tyre are designed to help shed water from a wet road as effectively as possible, or, if it’s a four-wheel drive tyre, the tread might even have grooves designed to flick mud out of the tread or have grip on the tyre’s shoulder to help give traction when driving in mud ruts. But back to wet roads.

A new-ish tyre will displace around 15L of water every second… by comparison, a ‘wet tyre’ on a Formula One car will shed around 60L or more of water every second.

Car driving in rain water tyre

As the tread wears down the tyre’s ability to shed water is reduced, increasing the chance of aquaplaning on the road, this is when your tyre hits a patch of water on the road and skims across the surface of the water, potentially losing control.

What are tread depth indicators?

These are rubber noggins that help to indicate when the tyre has worn out, but don’t rely just on them. Checking your tyres regularly will mean you’ll know when your tyres are worn out. The tread depth indicator is a little moulding in the tyre that, will, as the tyre wears down eventually sit flush with the surface. When this happens, your tyre is stuffed and ready for immediate replacement.

Tread Depth Indicator on a car tyre


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Practical Motoring

The team of journalists at Practical Motoring bring decades of automotive and machinery industry experience. From car and motorbike journalists to mechanical expertise, we like to use tools of the trade both behind the computer and in the workshop.


  1. I have an MX5 I bought new in 2011 that has only travelled 15000km and I’m still running on the original tyres. A year ago I was told when getting the annual rego check that I would have to replace the tyres because they were past the use by date .
    Just for confirmation I checked with the RTA technical department they said that as long as the tyres are not worn or damaged and were in good condition there was no reason why the car should not pass the rego check, I also checked with our local tyre service who told me the tyres were almost as good as new and had a lot more kms in them. My dealer also checked with the RTA and was happy with their explanation.
    The RTA used the example of all the old classic cars that are probably getting around on older tyres.
    I will probably be purchasing new tyres in the near future but I thought this was an interesting situation.

    1. Phil, I would recommend replacing your tyres immediately. That is way to old, I replace tyres at the 5 year mark irrespective of distance traveled.

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