Car Tire Buying Guide: Size and Age Before Price

Tyres are the only point of contact between the car and the road, and everything the brakes and suspension do passes through four patches no bigger than the palm of your hand. Despite that, tyres are usually bought on price alone. This guide covers what to know before buying, and how to read the tyre itself.

Read the size on the sidewall

Every tyre carries a line on its sidewall such as 205/55R16 91V, and each part means something specific:

Element	What it means
205	Tyre width in millimetres
55	Sidewall height as a percentage of width
R	Radial construction
16	Rim diameter in inches
91	Load index
V	Speed rating

The size has to match what your car's manufacturer specifies — you'll find it in the owner's manual or on a label inside the driver's door. Changing the size affects the odometer reading and how the car behaves, and shouldn't be done without reason.

The manufacturing date: the number nobody asks about

On the sidewall is a four-digit number inside an oval: the first two digits are the week, the last two the year. A tyre ages with time even unused, because the rubber gradually loses its flexibility. A "new" tyre made years ago isn't really new.

Ask for this number before buying and read it yourself on the tyre. It is the single biggest thing separating a good purchase from a poor one in the tyre market.

What to inspect before buying

• Tread depth: even across a new tyre; on a used one, check the depth at three points across the width.
• Sidewall cracking: a sign of aged rubber and reason enough to refuse.
• Bulges: any bulge in the sidewall means internal damage — don't buy it and don't use it.
• Uneven wear: on a used tyre, wear on one side means the previous car had a suspension or alignment problem.

Four or two?

Replacing all four together is best because it preserves balanced behaviour. If only two are possible, fit them to the rear axle even on a front-wheel-drive car — the weaker tyre at the back makes the rear break away first, which is harder to control than the front sliding.

After fitting

Have the wheels aligned and balanced, and check pressures regularly — the wrong pressure shortens tyre life, raises fuel consumption and affects braking. Check the spare's pressure too; it's what you'll need at the worst moment.

For buyers

Browse the parts listings, and read OEM versus aftermarket for where the original is worth its price.

In short

Read the size from the sidewall and match it to the manufacturer's specification, ask for the manufacturing date and read it yourself, inspect for cracking and bulges, and fit new tyres to the rear if you're only replacing two.