Tyre size guide: how to read your tyre size
Your tyre size is moulded into the sidewall of every tyre and printed on the tyre placard, usually inside the driver’s door frame. It looks like 205/55R16 91V. Once you know it, you can buy tyres online with confidence: search by that size and every tyre listed fits it.
What each part of a tyre size means
- 205 is the tread width in millimetres, measured wall to wall.
- 55 is the profile, also called the aspect ratio: the sidewall height as a percentage of the width. Here it is 55% of 205 mm, about 113 mm.
- R means radial construction, used by almost every car, 4×4 and van tyre today.
- 16 is the rim diameter in inches. It must match your wheel.
- 91 is the load index. 91 means up to 615 kg per tyre.
- V is the speed rating. V means the tyre is rated to 240 km/h.
People write the same size in different ways: 205/55R16, 205/55 R16 and 205 55 16 all mean the same tyre size.
Where to find your tyre size
Look on the sidewall of your current tyres, between the brand name and the rim. The tyre placard on the driver’s door frame (sometimes the glovebox lid or fuel flap) lists the factory sizes for your vehicle, with the minimum load index and speed rating for each. If your current tyres don’t match the placard, follow the placard or ask a qualified tyre fitter.
Load index and speed rating rules in Australia
Replacement tyres must have a load index and speed rating at least equal to what your vehicle’s tyre placard lists. A higher rating is fine; a lower one can make the vehicle unroadworthy and may affect your insurance. Utes, vans and 4x4s that carry weight or tow need particular care with load index.
| Load index | Max load per tyre | Speed rating | Max speed |
|---|---|---|---|
| 87 | 545 kg | Q | 160 km/h |
| 91 | 615 kg | S | 180 km/h |
| 95 | 690 kg | T | 190 km/h |
| 100 | 800 kg | H | 210 km/h |
| 105 | 925 kg | V | 240 km/h |
| 110 | 1,060 kg | W | 270 km/h |
| 115 | 1,215 kg | Y | 300 km/h |
4×4, light truck and van tyre sizes
Some off-road tyres use a flotation size such as 31×10.50R15: about 31 inches tall overall, 10.5 inches wide, on a 15-inch rim. Light truck and van tyres often show two load numbers, such as 109/107S: the first applies when the tyre runs on a single wheel, the second when tyres run in pairs on a dual axle. Older van sizes such as 185R14C have no profile number and a tall sidewall built for load; the C means commercial.
Can I change my tyre size?
Changing size changes the overall diameter, which affects your speedometer, ABS and stability control, and can rub on suspension or bodywork. Stay with a size on your placard unless a qualified tyre fitter has checked the change for your vehicle. Larger sizes on 4x4s may also need engineering approval in some states.
When to replace your tyres
The legal minimum tread depth in Australia is 1.5 mm across the main grooves, where the tread wear indicators sit. Wet grip falls well before that, so many drivers replace tyres at around 3 mm. Replace tyres sooner if you see cracks, bulges, cuts or uneven wear, and check the date code on older tyres: the four digits after DOT show the week and year of manufacture.
Buy your size
Ready to buy? Search all tyres by size, or start with car tyres, 4×4 and SUV tyres or ute and van tyres. Every tyre can be delivered Australia-wide or fitted by a Tyroola fitting partner near you.