When Do I Need to Change My Car Tyres?


As a basic rule of thumb, car tyres should be changed every 30,000 to 45,000km that you travel. However, it’s important to check your tyres every 6 to 8 weeks for wear and tear, as they play an important role in keeping you safe on the road. 

Here are some of the key indicators that you should look out for when checking your car tyres: 

Tread Depth

The sole purpose of the tread on your car tyres is to create grip when driving. Low levels of tread are a common contributor to motor vehicle accidents and one of the most common reasons you’ll need to change your tyres. 

The “tread depth” of your tyres is defined as the vertical height between the top of the rubber to the bottom of the deepest grooves. 

New tyres come with a tread depth of between 8mm and 12mm. In normal driving conditions, the tread should reduce by approximately 1mm every 5,000km. 

Within Australia, the minimum legal tread depth is 1.5mm. This minimum depth is indicated by the “wear indicator bars” on the tyres which are situated at the base of the main groves. However, most tyre manufacturers and shops recommend that you change your tyres once the tread depth reaches 3mm. 

In extreme cases of low tread the fabric or cords will show, which are situated beneath the tread – When you can see these items you should stop driving and replace the tyres immediately. 

Punctures to the Tread

Tyre punctures are often caused by glass, nails and screws left on the road that pierce the surface of the tyre. They are very common in Australia, particularly in areas with high levels of construction. 

Surprisingly, they will not always lead to a loss of air pressure, this will only occur when the puncture is deep enough to break the wall of the tyre. However, it pays to repair even small punctures, as they can lead increased damage over time. 

Tyre punctures can often be repaired without having to replace the tyre. In most cases, if the hole or cut is less than 6mm and does not penetrate the fabric or cords beneath the treat, they can be repaired by a qualified repairman. 

Checking for punctures yourself in between visiting your tyre shop is relatively easy. Feel around the tyre (being careful of sharp objects) as well as using your eye to look for any third party objects. 

Damage to the Sidewalls

The sidewall is the side area between the tread and where the tyre meets the rim, and serves several purposes including – 

  • Preventing air from escaping
  • Protecting the body plies
  • Increasing lateral stability
  • Helping to provide a smooth ride by absorbing shock
  • Markings to demonstrate the tyre brand and size. 

Sidewalls can show numerous different types of damage including – 


Cracking to the sidewall is typically caused by long-term exposure to heat. The cracks can reduce the ability of the vehicle to handle large increases in load when turning and in extreme cases can lead to the tyre blowing out. 

Tearing or Abrasion

Grazing against kerbs or driving over potholes and other structures can lead to tears within the sidewall. In some cases, the tyre will show a bulge rather than a visible tear. If a bulge is present within the sidewall, this can indicate damage to the cords within the tyre. 


Punctures are more likely to occur within the tread, although large nails and other sharp objects can sometimes puncture the sidewall of the tyre. Because the materials used to produce the sidewall is softer than the tread, it is recommended that you replace tyres with any damage to the sidewall, rather than trying to repair them. 

Damage to the Beads

The bead is the edge of your tyre that sits directly against the car rim. It is a high-strength steel cable which is coated in rubber. 

When a car tyre is fully inflated the tyre keeps the bead within it’s groove. 

Damage to tyre beads is generally caused by bad techniques when removing or fitting your car tyres. To avoid this, you should always engage the services of a qualified tyre fitter as in most cases, this type of damage cannot be repaired. 

What Can Happen if I Fail to Change My Tyres?

Failing to regularly check and change or repair your car tyres when damage occurs can lead to several critical issues – 

Buildup of Heat

Driving your vehicle causes friction between the road and your tyres. Driving on bald tyres will create an increased level of friction and heat, which over time can cause damage and potentially lead to tyre blowouts. 

Low Air Pressure

Low levels of air pressure can cause several issues including – 

  • The remaining tread will wear out faster, meaning you will have to replace the tyres sooner than you otherwise would have
  • Car mileage can be reduced making it more expensive to drive your vehicle
  • When taking corners at a reasonable speed, low pressure tyres can cause the sidewall to flex which leads to lower levels of grip
  • Problems can also arise when trying to stop quickly with lower levels of grip. 


This occurs when there is a layer of water between the road and tyre tread. Most tyre treads contain specialised grooves that channel the water away and maintain the grip of the vehicle. When the tread is worn or bald, these groves are diminished which can cause the vehicle to lose grip, become difficult to control and often lead to an accident. 

Purnell Tyres

Purnell Tyres are a car tyre shop located in Queensland, Australia. They offer a huge range of car tyres and rims to buy online or from their shop in Waterford.