What Do The Numbers On Tyres Mean?

The series of numbers begin with a letter, and this denotes the tyre type. Passenger car tyres will include a P, while you'll see LT on tyres more suitable for light trucks.

The section width of a tyre is measured on an ideal width for which it was made. It is measured from the maximum width of the midpoint of the tyre's sidewall to the same point on its opposing sidewall. The width of a tyre also indicates the vehicle it's suitable for. A passenger car tyre might have a section width of 185, while a light truck's section width might be 215. 

The aspect ratio is calculated by expressing the height of the tyre's sidewall as a percentage of the section width. The higher the ratio, the higher the tyre's sidewall. This is a very important sizing calculation - a higher ratio will cause tyres to absorb shocks and travel more smoothly but means your tyres might not handle well around corners. A lower ratio will lead to a bumpier ride and more vibrations throughout your vehicle but will result in better steering and handling capacity.

You'll then notice a letter, which indicates the type of tyre construction. Car tyres usually carry letters R and D.
 
If you see an R on your tyres, it means there are radial layers running across the tyre. This affords a fantastic grip, lower rolling resistance, and great longevity.
 
A D indicates your tyre has been constructed with diagonally-crossed nylon cords. These tyres tend to carry higher resistance against damage, and higher rolling resistance. They're most popular for motorbikes and trailers.

The rim diameter of a tyre is calculated in inches. Diameter is taken from the tyre's wheel flange where it is seated across to the same point on the opposing side.

The load index or load rating determines how much a tyre can carry while travelling at its maximum speed rating, and not going beyond 210kph. It's usually calculated alongside the tyre's speed index. A higher index means the tyre is more suitable for heavy-duty vehicles, as it's able to support weight more easily.
 
The load index is crucial for ensuring your safety. Carrying too much weight for your tyres will put them under stress and create excessive heat, which can lead to devastating consequences. 

The speed index is identified by a letter. It refers to the maximum speed capacity of a tyre when it operates at its highest load-carrying capability. If you see a "Y" marked on your tyres, it means your tyres can be operated safely at a maximum speed of 300kph. 

For affordable tyres that don't compromise on quality, come to A1 SuperCheap Tyres. Our team has years of experience in the industry and is passionate about providing high-standard, performance-based tyres for every vehicle, and about maintaining excellent customer care and service. And it's not just tyres we offer - we can also repair brakes and batteries and conduct minor servicing. Come and check out our great range of stock, or give us a call on (07) 5539 5326 to learn more about us and explore your needs with our friendly team.