Understanding More Tyre Terminology

Many drivers will not need to know any more than the basics of what is important in a tyre. Any tyre dealership can assist you with the more advanced terminology. But to really makes an informed decision, you may want to ask more complicated questions.

Tread Design Terminology

Each aspect of the tread design has a purpose. When a tyre has a unique tread design it mixes additional features to improve the safety and performance of your drive. There is no ultimate combination of these features and many of the features have a similar purpose.

Shoulder Grooves – Helps to reduce running noise.

Ladder-Like Grooves – Improves stability when going off road.

Pattern Grooves – Offers superior braking force.

Circumferential Grooves – Enhances grip and stability with larger loads.

Circumferential Grooves – Enhances grip and stability with larger loads.

Variable Groove Shoulder – Reduces shock, especially off the road.

Asymmetrical Pattern Design – Provides strong grip.

Continuous Pattern Blocks – Increases stability.

Stair-step Tread Grooves – Minimises stone retention.

Load Index (LI)

The Load Index (LI) rating follows an international standard. It determines how much weight each tyre is capable of carrying. Fitting a tyre with a Load Index that is too low will compromise on safety. It makes sense that a 20-inch tyre can carry more weight than a 13-inch tyre. But every size of tyre can come with a different Load Index rating. Your vehicle manual will include details on the recommended Load Index rating for your vehicle. If in doubt, always buy new tyres with the same or higher Load Index rating than your existing tyres.

Load Index is printed on every tyre. You can use the table below to calculate the load in kilograms. Remember that Load Index refers to the weight each tyre can carry. A LI score of 98 means each tyre can carry 750kg. That means a total of 1500kg spread over the axle when the weight is distributed evenly (750 x 2 tyres on the axle).

Reinforced Tyres (XL)

Some tyres have been specially reinforced to carry more weight. This is indicated with the XL acronym. These tyres are naturally more expensive because of the technology and materials that make the tyre stronger. XL tyres are commonly required when you are carrying more passengers – for example if you drive a saloon car with more than five seats.

XL is an immediate indication that the tyre is reinforced. However, this improved capability is already reflected in the Load Index rating. So XL does not mean the tyre can carry extra weight beyond the Load Index rating.

Section Width (width)

The maximum width of the tyre at its widest point. This is measured from the inner sidewall to the outer sidewall when there is no load placed on the tyre – i.e. not when it is fitted to a vehicle. Section width is measures in millimetres.

Standard Rim Width

Rim size is the starting point for selecting a tyre and refers to the diameter of your rim. Each tyre also has a standard rim width measurement

Tyres are manufactured to fit on many vehicles and absorb the impact of many conditions. Because their sidewalls are flexible, the same tyre can fit on rims with different widths. But, of course, a single tyre can only fit on one rim diameter size.

Standard rim width is measured in inches. The figure shown in the tyre specifications refers to the ideal rim width for the tyre. You will also be able to fit the tyre on a rim that is slightly wider or narrower.

Groove Depth

This is a vertical measurement, from the surface of the tyre to the bottom of the tyre’s deepest grooves. Tyres will naturally wear over time, so the groove depth will decrease as rubber is worn off the tyre.

Blacklion presents groove depth measurements in millimetres.

The legal minimum limit for tyre groove depth in the UAE and Oman is 1.6mm. When you wear your tyres down to 1.6mm groove depth then they must be replaced.

Max Inflation Pressure

This is the highest pressure a tyre can be inflated to. It is measured in kilopascals (kPA).

Which Tyres Will Fit My Vehicle?

You are not restricted to a single size of tyre.

Many different tyres will fit on your vehicle and checking tyre size is much easier than you may realise.

Find the Size of Your Existing Tyres

Knowing your existing tyre size is the easy first step in buying a new tyre.

Knowing your existing tyre size is the easy first step in buying a new tyre.

Cross Reference With Vehicle Manual

Because many tyres can be fitted on your vehicle, you are not always limited to buying new tyres the same size as your existing tyres.

Your vehicle manual includes important information about the minimum requirements for any tyre that is fitted. Some of this information can also be found on a manufacturer’s sticker sticker placed on the driver side door – it may also be in the glovebox. Look for:

SS (Speed Index) – The minimum speed index rating that can be fitted.

LI (Load Index) – The minimum load index rating that can be fitted.

Size – Most manuals include a recommend size. Check with your tyre dealer because this recommended size is not the only size that will fit.

You should never buy tyres that don’t meet the minimum recommended requirements. You can sometimes buy tyres that exceed the maximum recommended ratings, but you may be paying more for features that are not necessary.

Can I Buy Different Sized Tyres

Yes. If you are buying a new set of four tyres it is possible to buy tyres with a different size to your existing tyres. Not all tyres will be suitable but many people are surprised at the number of different tyres that are suitable.

No. If you are replacing one tyre it must be the same size as your existing tyres. It’s widely recommended to replace at least two tyres at once, so the tyres behave the same on one of your vehicle’s axes.