Why Tyre Pressure Matters
Your tyres are the only point of contact your car has with the road. Incorrect tyre pressure affects everything from braking distance to handling in wet weather. Under-inflated tyres increase fuel consumption and wear out the outer edges faster, while over-inflated tyres wear out the center and decrease traction.
How to Check Air Pressure Correctly
1. Find Your Manufacturer's Recommended PSI
Don't look at the tyre sidewall for the correct air pressure; that number is the maximum safe pressure, not the recommended one. You can find the correct PSI (Pounds per Square Inch) on a sticker located on the driver's side door jamb, or in your owner's manual.
2. Check When Tyres are "Cold"
It's crucial to check tyre pressure when the tyres are cold—meaning the car hasn't been driven for at least a few hours, or driven briefly at low speeds. Driving heats up the air inside the tyre, causing it to expand and giving a falsely high reading.
3. Use a Reliable Tyre Pressure Gauge
Remove the valve cap and firmly press the gauge onto the valve stem. A brief hiss of air is normal. Read the number and compare it to the recommended PSI. Add or release air as necessary.
Checking the Minimum Safe Tread Depth
In Australia, the minimum legal tyre tread depth is 1.5mm. However, performance drastically decreases below 3mm, especially in wet conditions.
- The Tread Wear Indicator (TWI): Look for small raised rubber bars lying deep within the grooves of the tyre tread. If the tread block is worn down to be flush with these indicator bars, your tyre is no longer roadworthy and must be replaced immediately.
- The 20-Cent Coin Test: Place an Australian 20-cent coin into the tread groove. If the tread barely touches the platypus’s bill, your tyre tread sits at roughly 3mm. If the bill is clearly visible, you need new tyres soon.