Can you speak tyre - part one
Tuesday, 30 July 2019
The markings on the side of a tyre can resemble hieroglyphics if you aren’t sure what you’re looking for.
Organising a new set of tyres should be high on any pre-road trip agenda.
If you’re about to start searching for a new set of tyres for your car, you need to know the basics, so you can be sure you get the right rubber.
Here’s an easy guide to impressing your mechanic and understanding the numbers, letters and dots on your tyres.
The three largest numbers on your tyre’s sidewall are the most helpful.
They indicate the tyre width, profile (height) and the diameter of the wheel they are fitted to.
Let’s get real world on it. Grab a pen and paper or snap a photo of the numbers on your tyre sidewall.
The example we will use here is 235/45R17.
The first number is the easiest and measures the width of the tyre in metric millimetres. 235 means your tyre is 235mm wide.
The second number refers to the profile of the tyre or the height of the tyre’s sidewall.
The number isn’t in millimetres but is instead an aspect ratio measurement of how the height relates to total width.
In our example, the tyres profile is 45% of the total 235mm width.
Unnecessarily tricky? Maybe, but stick with us.
R means radial which refers to a common tyre construction for passenger vehicles.
The final number is a measurement in inches of the diameter of the wheel the tyre will be fitted to.
In this case, 17 means the tyre is fitted to a 17-inch wheel.
Yes, inches. Tyres mix metric and imperial measurements. Just to keep you on your toes.
WHAT’S WITH THE DOTS?
Seeing spots? Don’t worry, the yellow dots on your tyres are there for a reason.
These splotches of primary colour are called ‘balance dots’.
When a tyre is manufactured, perfect balance is extremely rare.
This is why when new tyres are fitted, they are ‘balanced’ with small sticky weights to ensure they roll smoothly and don’t cause vibration or uneven wear.
The yellow dot on the tyre indicates to the tyre fitter where the lightest part of the tyre’s sidewall is.
They will generally line that part of the tyre up with the valve stem, which evens things out and reduces the need for balance weights.
THE OTHER NUMBERS
“That’s not all the numbers on my tyre!” I hear you shout.
Take it easy! If you have already mastered the basics, there is definitely more information your tyre manufacturer has offered the advanced tyre diviner.
These include construction date, load rating, tread wear rating and speed rating.
Stay tuned for our advanced guide to tyre reading, and we’ll get into the nitty-gritty (even those mysterious red dots) in Part Two.
If you're over trying to learn the language of tyres, fear not.
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