Tyre Information

Understanding the markings on the sidewalls of your car tyres will help you choose the right replacements for your car.

The letters and numbers on the side of your car tyres relate to their size, dimensions, composition and capabilities.

Here’s what each section of the code means, using the tyre size and specification 175/65 R14T as an example:

  • 175 Tyre width in mm
  • 65 Tyre sidewall profile – sidewall height expressed as a percentage of its width
  • R Radial (rather than a cross ply)
  • 14 Diameter of the wheel rim, in inches
  • T Speed rating which must match or exceed the maximum speed of your car.

Car tyre speed ratings

  • S 180km/h or 112mph
  • T 190km/h or 118mph
  • U 200km/h or 125mph
  • H 210km/h or 130mph
  • V 240km/h or 149mph
  • W(ZR) 270km/h or 168mph
  • Y(ZR) 300km/h or 186mph
  • ZR Above 240km/h or 149mph

So the tyre we used as an example is only suitable for use on cars with a maximum speed of 118mph (or less). Tyres available in this size and specification include the Dunlop SP 30, Firestone’s Multihawk and the Continental EcoContact 3.

Your car’s handbook will tell you the minimum tyre speed and load ratings you should go for. Once you know the size and type of tyre you need, head over to our tyre reviews to find the best tyres we’ve tested.

Nitrogen Tyre Inflation

You know you should check your tyre pressure regularly, but why?
Correct tyre pressures mean that your tyres grip the road as they should.
Incorrect tyre pressures can cause unnecessary wear on your tyres which means they could wear unevenly or even need replacing prematurely.

Low tyre pressures can mean that your tyre creates more resistance to movement, this means that more energy is required to move your car meaning higher fuel consumption. Which means that maintaining your tyres at the correct pressure could help save you money on fuel and reduce the amount of CO2 you produce from your vehicle.

Molecule size & Pressure Temperature Moisture
Nitrogen molecules are slightly larger than oxygen and so seep out of the tyre about 3 – 4 times slower than compressed air. This means you will see a decrease in pressure of around 1psi every 5 months. Therefore, inflating your tyres with nitrogen means that the tyre pressure will stay correct for longer.

Wheel Alignment & Tracking

Incorrect alignment can result in rapid irregular tyre wear and can even affect the handling and safety of the vehicle.

Wheel alignment, or tracking, is the process of ensuring your vehicle’s wheels are set to the optimum position, as per the car manufacturer’s specifications, so that tyres wear evenly. Incorrect wheel alignment can be caused by hitting a kerb, driving into a pothole in the road or by excessive wear to steering or suspension components. It is important to get your wheel alignment checked annually to ensure you get the most out of your tyres.