What do the numbers on tyres mean?

Tyres are arguably the most important safety equipment on our cars – and often the most neglected. All braking, accelerating and steering depends on reliable tyre performance. The more challenging the road conditions, the more crucial it is to have four tyres with decent tread, proper air pressure and solid grip.

Most of us don’t give much thought to our tyres but we should – because they matter. For example, have you ever wondered about all those mysterious numbers embossed on the sidewalls of your tyres and what they mean? Let’s look at a typical example:

P 215/65 R15 90H

Now, this may look like gobbledygook but each number and letter supplies important information about your tyre. The P tells you the tyre is rated for a passenger vehicle. The number 215 indicates the section width in millimeters. 65 is the aspect ratio. The R informs you it’s a radial-ply tyre and 15 is the wheel rim diameter in inches. 90H designates the tyre’s load and speed rating.

So, let’s break all of that down:

Tyre type

In this case, P means passenger tyre. If it was a light truck tyre, it would say LT instead. A temporary spare tyre would have a T.

Section width

This is simply the tyre’s width from sidewall to sidewall – in this example, 215 mms.

What is aspect ratio on a car tyre?

This is the tyre’s sidewall height expressed as a percentage of the tyre’s section width. For this tyre, the sidewall height is 65% of its 215mm width.

Tyre construction and wheel width

In this instance, the R lets us know it’s a radial tyre. Other construction types include D (diagonal) and (B) bias construction. The 15 means the wheel rim diameter is 15 inches.

Load index and speed rating

The 90H indicates the maximum load-carrying capacity and speed at which the tyre can operate safely – but you’ll need to glance at a Load Index Table and Speed Rating Table to decode them. In this case, the 90 equates to a maximum load of 600kg per tyre and the H indicates a maximum speed of 210km/h (obviously, speed limits apply regardless of speed index ratings).

What are the other speed ratings?

Speed rating letter	Maximum speed in km/h
N	140
P	150
Q	160
R	170
S	180
T	190
U	200
H	210
V or Z	240
W	270
Y	300

Let’s take a look at a table of load indexes:

Load index number	Maximum load in kilograms
81	462
82	475
85	515
86	530
87	545
90	600
92	630
95	690
96	710

Although there can be slight variations in the way tyre brands are labeled, the basic information is the same. The most important thing is to make sure you have the right size/shape tyres for your car and that you check them regularly for wear and tear and correct pressure. Well-looked-after tyres make for a safer drive. ^{[i]  [ii] [iii]  [iv]}

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^[i] https://www.jaxtyres.com.au/knowledge/tyres/tyre-talk-what-do-the-numbers-mean

^[ii] https://www.tyrepower.com.au/tyres/tyre-tips/reading-the-tyre#:~:text=For%20example%2C%20the%20code%20on,65%25%20of%20its%20width).

^[iii] https://practicalmotoring.com.au/car-advice/how-to-read-a-car-tyre/

^[iv] https://www.caradvice.com.au/286485/tyre-hieroglyphics-explained/

Disclaimer: This information is general in nature only and does not constitute personal advice. While Chasing Cars has endeavoured to ensure the information we’ve relied on is accurate and current, we do not guarantee it and accept no liability for this information. Chasing Cars recommends you obtain specialist advice specific to your individual circumstances before purchasing any motor vehicle.