Did you know that the Australian government insists that you do not drive a car that is fitted with tyres worn down past a certain level? However, if you are aware of this, did you know that the tyre manufacturers themselves are even more cautious than those government watchdogs and recommended you change any covers that are still classified as "legal" by regulators? This can all be quite confusing to an average car owner, so what do you need to consider if you haven't checked the condition of your tyres for some time?
Tyres that are sold in this country are equipped with a special measuring block which is placed within the tread and is designed to give an instant, visual indication when the tyre has worn down to its legal limitation. These small measurement blocks are set into the construction of the tyre far below the level that touches the road when the tyres are new. As friction deteriorates the covers with the passage of time, the tread will wear down inexorably to the measurement level.
How Tyres "Go off"
The government sets this "minimum" tread depth at 1.6 mm, but you should nevertheless understand how the performance of the tyre will degrade considerably as it is approaching that particular point. When the rubber attached to a tyre carcass starts to age it will heat up more than it otherwise would during normal usage. As it does so, it may tend to move around to a certain extent within the overall construction and this has an effect on how the car handles, especially during wet weather. This is why the manufacturers themselves suggest that you consider changing the tyres when the tread depth is 3 mm instead, as this still gives an acceptable level of performance and safety in typical conditions.
How to Check
If you don't know where to look to find those tread depth indicators fitted to your tyres then you can nevertheless get into the habit of checking the depth by using a special indicator available in most vehicle accessory stores. You'll be able to insert this plastic ruler into the tyre tread to see exactly how much is left. If you don't have one of those special tools, you can use a ten cent coin. Once again, insert into the tread of the tyre and if the outer ring is obscured when you do so, you've still got enough tread left as the tyre is not yet at its minimum legal limit.
Always Be Safe
Have a word with your tyre fitting specialist if you've noticed some abnormal wear to your tyres, so that you are always legal and safe on the road.