In a survey of 1000 drivers aged 18 to 25, one quarter of them admitted to never having checked their tyre pressures, and one third had never checked the tread depth. 62% underestimated the minimum legal tread depth of 1.5mm (which must be within all principal grooves containing moulded tread depth indicators, or if they are not available, across 75% of the tyre’s width). However, tyre performance drops off significantly in the wet at tread depths below 3mm, so drivers should look to replace tyres when they reach this level rather than wait until they’re 1.5mm.
Ingenie Insurance ran the survey and also found that 82% of people underestimated the fine for having a defective tyre in the UK where they are way more draconian than in New Zealand (UKP2500, or about NZ$5000, plus up to 6 points on the licence). Our fines are $150-370, with a maximum penalty of $500. The other thing to be aware of is that insurance companies may refuse to pay out for a claim if a tyre is obviously defective.
Drivers can stay safe by setting a diary note each month to check tread depth, pressure and for any obvious signs of damage such as gouges, bulges or cracks in the sidewall.