Understanding your Tyre Readings (195/55 R16 87V)

On the sidewall of all tyres you can find the Load Index and Speed Symbol for that tyre (following the key sidewall markings) for example 105 S.

LOAD INDEX

The load rating (represented by the numerical value) is related to the maximum weight that tyre can carry. So in this case 105 would refer to a load capacity of 925kg, with most passenger vehicle load indexes range from 62 to 126.

In all instances the tyres load index must meet or exceed the value displayed on the vehicles placard.

SPEED SYMBOL

The speed category symbol, for example ‘S’, indicates the maximum speed at which the tyre can carry a load corresponding to its load index. So in this case, ‘S’ would refer to a maximum speed of 180km/hour

See the chart below for a full list of speed symbols and their applicable values.

*A tyre with ZR symbols have a speed capability of over 204km/h. Your T-Mart can always consult with the tyre manufacturers to ascertain the tyres actual speed capabilities.

The legal speed symbol requirements vary by state, please check with your local T-Mart.

PLY RATING

Ply ratings identify the load carrying capacities of a tyre in terms of plies. Ply rating originally referred to the number of cotton layers used to strengthen a tyre’s casing. Today, when tyres are labelled 10-ply for example, they are no longer actually constructed of 10 individual layers of cotton, but they do offer the equivalent strength. Over time, steel ply and radial construction replaced cotton, leading to a new distinction: Load Range. Load Range identifies the maximum amount of weight that can be placed on a tyre horizontally, which varies depending on tyre size and inflations limits.

Brand and Pattern

All tyres feature the brand and pattern description on the sidewall. In this instance the brand is Bob Jane and the pattern is Xenon Z7.

Sidewall Markings

• Width: Tyre measured in millimetres from the two widest points.
• Profile: The aspect ratio of the tyre, which is the height of the sidewall as a percentage of the width.
• Wheel size: Diameter of the wheel rim that the tyre is designed to fit, measured in inches

Directional Marking

Directional tyres have been designed specifically to operate best when rotating in one direction. The tyre pattern is usually in the shape of an arrow with grooves running from the centre rib (middle) of the tyre to the outer shoulders. First engineered for racing in wet conditions, directional road tyres have excellent wet weather performance, due to their ability to displace large amounts of water from the road surface, while providing directional stability.

If you have a pair of directional tyres on your vehicle, they will usually have either an arrow or similar symbol indicating the direction they are designed to operate.

Speed Rating, Tyre Load & Pressure

• Load Index: The load index is a numerical code associated with the maximum load a tyre can carry when inflated to operating pressure.
• Pressure: Nearly all manufacturers print a maximum inflation pressure on the sidewall the tyre. It is important to note that this is generally not the recommended operating pressure for that tyre. If you are unsure of the correct inflation pressure for your tyres or the pressure description is missing, simply enquire at your local T-Mart or reference the tyre placard on your vehicle.
• Speed Category Symbol: This indicates the maximum safe operating speed for the tyre when carrying a load within its load index rating.

Source: http://www.bobjane.com.au/

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