When should you
replace your tyres?

It is the question we get more than any other across the counter. People know worn tyres are a problem, but nobody wants to replace good rubber a year early either. Here is how we call it in the workshop, the numbers that matter, and the signs that mean it is time whatever the tread says.

The legal limit is 1.5mm, but do not aim for it

In Queensland, and right across Australia, a tyre is illegal once the tread wears below 1.5mm across the pattern. Every tyre has moulded wear indicators, small raised bars sitting at the bottom of the main grooves. When the tread wears down level with those bars, you are at the legal limit and the tyre has to come off.

The trap is treating 1.5mm as a target. It is a minimum, not a goal. Wet grip falls off a cliff well before that point, because there is less groove left to channel water out from under the tyre. By the time you are legal-but-barely, stopping distances in the rain have already grown a long way.

The 20 cent test you can do in the driveway

You do not need a gauge. Take a 20 cent coin and slot it into the main tread groove. The platypus sits about 3mm in from the edge of the coin. If the tread does not reach the platypus, you are down around that 3mm mark and it is time to start thinking about new rubber. Do it in a few spots across the tyre and on both edges, because tyres rarely wear evenly.

Age matters even if the tread looks fine

This one surprises people. Rubber is a chemical, and it ages whether the car is driven or not. A tyre that has sat on a caravan, a trailer or a weekend car for years can have plenty of tread and still be unsafe, because the rubber has hardened and started to crack. Heat and UV, which we get plenty of out here, speed it up.

Every tyre carries its birth date on the sidewall. Look for a four digit number inside an oval, the last part of the DOT code. The first two digits are the week, the last two are the year. A tyre reading 3619 was made in the 36th week of 2019. As a rule we treat tyres over five years old with caution and recommend replacing anything past ten years regardless of tread, which is what most tyre makers advise too.

The signs that mean replace it now

Tread and age are the slow measures. These are the ones that mean do not wait:

• Wear on one edge only. The inside or outside shoulder worn while the rest looks fine usually points at alignment or worn suspension. New tyres will do the same thing until the underlying cause is fixed, so it is worth a wheel alignment check at the same time.
• Cracking in the sidewall or between the tread blocks. Fine crazing is age. Deeper cracks mean the tyre is perishing and can let go.
• A bulge or blister. That is a damaged casing, often from a hard kerb or pothole hit. It can fail without warning. Replace it, do not wait.
• Vibration that will not balance out, or a repair that keeps losing air. Sometimes the tyre is simply done.

Do all four need to go at once?

Not always, but matching matters more than people think. If you are only replacing two, the new pair should go on the rear, even on a front wheel drive, because the back of the car losing grip in the wet is far harder to catch than the front. On a 4WD or all wheel drive it is different again, since a big difference in rolling diameter between axles can stress the driveline. If you are in that situation, ask us and we will tell you straight whether two will do or whether it is a set.

When in doubt, let us look

A tyre check takes a few minutes and costs nothing. We will measure the tread, read the date, look at the wear pattern and tell you honestly whether you have months left or whether it is time. If the budget option does the job for how you drive, we will say so. We stock the full range, from value through to the Falken flagship, so the advice is never about pushing the dearest tyre on the wall.