Woman inspecting tyres

Tyres Explained: The Rubbery Figures That Matter

Tyres. They’re black and round – what more do you need to know?

By Shell on Jan. 12, 2021

Actually, a lot. While your car has thousands of components, tyres are the final, crucial link between machine and tarmac. They contribute to how it cushions the bumps, accelerates, brakes and corners, how quiet it is and its fuel efficiency. The wrong tyres can not only make your car drive less effectively, they can potentially threaten your safety.

If you’re buying a new set of tyres for your car, here’s what you need to know.

Choosing the right tyre

On paper, this is pretty simple – just follow the tyre size, load rating and speed-rating recommendations listed in your owner’s manual.

Car companies spend a lot of time and money ensuring the tyres fitted to a car deliver a good compromise between grip, comfort, efficiency and wear. Fitting the same tyres will ensure your car drives as its makers meant it to.

But wait …

Here’s where the plot thickens. Car manufacturers typically only recommend a specific tyre size, not the brand. Shop around and you’ll find a variety of brands and variants within brands, from cheap to expensive, all in the one size range. So, which one is the best for your car?

The safe, easy choice is buying the same brand and model fitted to your car when new. Again, you’ll be piggybacking the car manufacturer’s development work and getting a tyre that definitely works well with your car.

Buying off the shelf

If factory-specification tyres exceed your budget or you would like to fit rubber with better performance, comfort or durability, or less rolling resistance, how do you narrow down your choices?

The truth is credible, market-wide comparative data on tyre performance, durability, wear and other long-term factors doesn’t exist, but some basic research can help paint part of the picture.

Tyre performance is sometimes assessed by third parties – look for group tyre tests in the motoring media and from consumer advocates such as Choice – and buyer feedback on the web can offer guidance.

If a particular tyre is also sold in the US, it will have a tread-wear rating that indicates its performance in that country’s Uniform Tyre Quality Grading System (UTQGS). The higher the number, the longer the tyre should last.

What the numbers mean

Tyres are categorised using a complex numbering/lettering system; for example, ‘205/40R18 86Y’. It seems a bit confusing but there’s a logic when you break things down.

The first three numbers refer to the sectional width of the tyre in millimetres when mounted and inflated, specifically between the sidewalls – how ‘wide’ it is. The next two numbers refer to the tyre’s aspect ratio. This relates the height of the tyre to its sectional width as a percentage – a smaller number basically means a ‘thinner’ tyre.

The letter that follows describes the internal construction of the tyre (in this case ‘R’ for radial), and the two numbers after that tell you what rim size, specifically the diameter in inches, the tyre should be mounted to.

The next two numbers are a code for the tyre’s load rating (in this case, ‘86’ for 530kg) and, finally, a letter for its speed rating (in this case, ‘Y’ for 300km/h).

Cutting the cost

Like almost any product in 2020, you can buy tyres from online or overseas traders who offer notably sharp deals.

The strategy can have its advantages, not the least price and the potential convenience of having tyres delivered and fitted, but you should be wary about laying down cash on an unfamiliar or unknown tyre brand.

Making tyres is a complex game and – like any engineered product – expertise accumulates. If it’s a brand with a long history in the industry, you can essentially trust its products will be roundly competitive. If the tyre brand has no market reputation or local feedback to guide you, you’ll have to take its word that its products are up to scratch. You might forgo the local product support offered by the big brands, too. So do your research.

If in doubt, consult your local tyre retailers. Their knowledge of the market can help guide you to a tyre that meets your specific needs. They can help ensure you get value for money out of your next tyres, not just a rock-bottom price.

Finally, don’t be tempted to buy second-hand tyres. Their shorter lifespan will likely wipe out any cost savings and they have a higher risk of defects, putting your safety and the lives of others at risk.


Viva Energy Australia Pty Ltd (“Viva Energy”) has compiled the above article for your general information and to use as a general reference. Whilst all reasonable care has been taken by Viva Energy in compiling this article, Viva Energy does not warrant or represent that the information in the article is free from errors or omissions or is suitable for your intended use.

Where information, recommendations, opinions or ideas have been sourced from third parties external to Viva Energy (Third Party Information), Viva Energy cannot be certain that the Third Party Information is accurate, current or complete, nor should a mention of any business, product, service or website of a third party be taken as a recommendation, approval or endorsement of, or warranty or claim regarding, that business, product, service or website.