Car 101: what most people don't know about tyre tread

Monday, 10 September 2018

A 2018 survey in New Zealand showed that only 37 per cent of drivers thought they knew the minimum amount of tread their tyres ought to have.

Do you know what the legal minimum amount of tread your tyres should have is?

A recent survey of 2,300 people by research company Canstar showed that only 37 per cent of people thought they knew what the minimum legal tread depth on a tyre was. But not all of them were actually right.

Of the 37 per cent who thought they knew the legal minimum, 10 per cent thought it was 1.2mm, while 5 per cent thought it was just 1.0mm.

Most tyres have wear indicators like these - when the tread is level with them, it is time to replace the tyre.

It is, as just 723 people out of 2,300 knew, 1.5mm.

However, it is not quite as concerning as the numbers might suggest, because of those who said they didn't know the legal minimum, the vast majority (88 per cent) actually guessed correctly or higher, with 56 per cent guessing 1.5mm and 32 per cent guessing 3.0mm. Although a worrying 11 per cent guessed only 0.5mm.

You can check the level of tread with a 20 cent coin - the bottom of the numbers is 2.0mm from the bottom of the coin.

* Car 101: five important bits under your car's bonnet

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Interestingly, while only 32 per cent of Gen Y respondents said they knew, a higher amount of them actually did (89 per cent), while a higher number of Baby Boomers claimed to know the correct amount (44 per cent), but only 80 per cent of them were actually correct.

Of course, while the legal minimum is 1.5mm, the more tread you have the better grip your tyres will have and the safer you will be, so it makes sense to check them regularly.

Most tyres have depth indicators that will be flush with the tyre tread when it has reached the minimum depth, but another easy way to check the depth of your tread is to insert a 20 cent coin into one of the grooves near the middle of the tyre - the bottom of the '20' is roughly 2mm from the edge of the coin, so if you can see the whole of the number, you need to start thinking about new tyres.

Tyre pressures also play a critical part in the footprint of your tyre, as well as the amount of wear - an under-inflated tyre wears far quicker than one at the correct pressure.

The Canstar survey showed that 43 per cent of people said they regularly checked their tyre pressures, while a (possibly more honest) 45 per cent said they never remembered. 12 per cent said they didn't know how.

There is a very easy solution to not knowing how, however; ask. Service station staff, your mechanic or a staff member at a tyre shop will all be happy to check for you and show you how to do it in the future.