Knowing where to tread

When faced with row upon row of black rubber with different brands and price points, it can be difficult to know where to start when it comes to buying new tyres for your vehicle. Here are some things you need to consider:

​Buy the right tyres for your car:

  • Every car will have a tyre placard sticker on it somewhere. It will have the correct tyre size, recommended tyre pressure, speed and load ratings.
  • Buying a tyre of a different size to that on the placard may have unintended consequences, including putting you speedo calibration out.
  • Stick with a known brand

Understanding tyre sizes:

  • Tyres haven’t quite managed to settle on metric or imperial measurements yet. All tyre fitment diameters are measured in inches, but the tread section is measured in millimetres. Add to that a number in the middle of the two that is a percentage and you have a recipe for confusion. For example, a tyre size of 215/65R16 95H means the tread width is 215mm, the sidewall height is 65% of the tread width (loosely 129mm) and the wheel diameter is 16 inches. The R indicates radial ply construction, and the 95H indicates the load capacity and maximum speed rating.

Tyre construction:

  • While there are many elements that go to make a tyre, the two main bits are the tyre carcass, which includes the bead, sidewalls and reinforcing that allows the tyre to hold air, and the tread belt that runs along the road providing grip in wet and dry conditions. Tyres are made from a combination of many things. The obvious one is natural rubber, but they also may include synthetic rubber, fabric carbon and other chemicals. The actual construction of the tyre might include wire and differing types of fabric. Modern technology has brought low rolling resistance tyres to the market, which claim to increase fuel economy.
  • Almost without exception all tyres constructed these days are designed to be used as tubeless.
  • Some vehicles are fitted with run-flat tyres so they don’t need to carry a spare tyre. If you do get a puncture with one of these, you often have to replace the tyre, as it can’t be repaired.

Tyre tread:

  • Tyre tread patterns are many and varied, some are quite closed and have narrow tyre grooves some have wide groves. Some have linear patters some have block patterns.  In very general terms a tyre with a wide block pattern tends to create a bit more tyre noise on the road, particularly on coarse-chip bitumen. The positive trade-off can sometimes mean better wet weather performance.

When are my tyres worn out?

  • All tyres must have tread wear indicators (TWI) (see pic below). These are slightly raised bump of rubber sitting at the bottom of the tread groves and go across the width of the tread. They are situated at regular intervals around the circumference of a tyre. When any part of the tread wears to a point where it is level with this raised TWI, then it is time to replace the tyre. The head of a match is also a good indicator it’s time to replace your tyres. Poke it in the shallowest part of the trad and if any of the head is above the tread, replace them.


 Looking after your tyres:

  • Tyre pressures should be checked regularly. I do mine monthly. Low tyre pressures can increase fuel consumption and lead to premature tyre wear.
  • Tyres should be regularly rotated front to rear. This evens out wear as often front tyres wear faster than rear tyres.
  • Tyres should be balanced when they are rotated and any signs of abnormal wear on the front or rear should be investigated for a suspension issue, and undergo a subsequent wheel alignment.
  • Always try and replace all four tyres together, at a minimum replace in pairs not individually. If you replace two tyres, by law you need to make sure they are the same size and construction as the remaining tyres on the vehicle.
  • AWD vehicle tyres should always be replaced as a full set as mismatched sizes (old and new) can cause issues with the drivetrain.

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