How can I tell the size and specs of my tyre?
The most common method used to identify tyres is a series of numbers and letters found on the sidewall of the tyre.
For example, the tyre may be labelled: 225/50R16 92V XL
What exactly are you looking at? Let’s break it down.
225 is the width of the tyre in millimetres, known as the section width. This measurement is taken from the widest point of its outer sidewall to the widest point of its inner sidewall.
50 is the height of the tyre sidewall as a percentage of the width, also known as the aspect ratio or profile. In this example, the tyre has an aspect ratio of 50, which means that the height of the tyre is equal to 50% of 225mm, so roughly 112.5mm.
R is the internal construction – the R stands for Radial. This is the most common type of tyre used today, making up 98% of all tyres sold.
16 is the diameter of the wheel rim in inches. A tyre and wheel diameter must always match before the tyre is mounted on the wheel.
92 is the maximum weight the tyre can carry, AKA the load rating.
V is the speed rating of the tyre and is always represented by a letter. The speed rating works hand-in-hand with the load rating. In other words, the speed rating is the maximum speed the tyre can reach when operating at its maximum load carrying capacity.
Some tyres may also have the letters XL after the speed rating (not shown on our diagram). This stands for Extra Load and means the tyre can be inflated to a higher pressure. This increases the tyre’s maximum load. Typically this is to do with larger types of vehicles like SUVs, or load carriers like utes and vans.
High Flotation tyres
Although commonly used in the farm and agricultural industries, flotation tyres have also become increasingly popular in off-road and all-terrain trucks and SUVs. To read the size of a flotation tyre, things are done a little differently:
For example: 32×12.50R15LT
32 is the overall diameter (in inches)
12.5 is the width in inches
R indicates that the tyre’s construction is radial (just like passenger and commercial tyres)
15 is the rim diameter (in inches)
LT indicates that the tyre has been constructed for a light truck
Wait up just one more moment – please keep in mind that when you’re buying new tyres, you need to keep your new tyre size about the same as the old size. This is because many speedometers and odometers use the rotation of the wheels to determine how fast, and far, the car is travelling. The figures you get from your dashboard are guessing that the circumference of your tyre matches with the manufacturer’s original specifications.