The basic labels-letters for tyres

 

175/70 R 13 82 T

 

 

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Speed rating index

 

Speed rating index indicates the maximum speed capability the tyre is designed for(in km/h).

 

 

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Load range index

 

 

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Wheel centering system

 

Wheel centering system includes alignment of wheel rims to be normal against the ground (horizontal) and paralell to each other. The purpose of the alignment is to extend tyre life and better navigation on smooth surfaces. However, geometry of a vehicle sometimes can be deranged which causes irregular ride reflecting the tyres, too. Non uniformly wearing of front and back tyres as well as sideslipping during driving can indicate irregular centering system. Sometimes it is necessary to align front wheels and sometimes all four wheels. It depends on the specific situation and the make of car

 

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Balancing wheels

 

Balancing is a method of stabilising wheel weight on opposite sides of the same shaft by adding lead rings on wheel rim. Centrifugal force influences the wheel as well as any other object while rotating around an axis. If it is not balanced (body mass is not equal on each side of an axis) it causes imbalance manifesting through steering wheel vibration even at speed of more than 70 km/h, or whole vehicle vibration.

In the process of balancing tyre can be stabilized by lead, discs or by puncturing. The best way is to balance all four wheels because a vehicle can vibrate although the front wheels have been balanced but the back wheels have not. Back wheels imbalance can be transferred and perceived even through the steering wheel or on the whole vehicle.

If balancing is not performed in time, tyres are worn faster and unequally,as well as bearings, shock absorber and other components of car suspension system. Every time tyres are placed on a wheel or replaced after repairing they must be balanced.

If a tyre or a wheel rim is askew, vibration can occure at some speed but before or after that specific speed, it stops. For example, between 80-90, 100-110 or 130-140km/h, or at small speed where a vehicle does not “shake” but performs so called dangling of steering wheel. It can be evaded by placing one or more new tyres and by changing or repairing a wheel rim if it is askew.

In the process of balancing different types of lead are used because of wheel rims differences. Inadequite lead can easily drop off the wheel rim thus causing the danger so it is recommended to pay attention to it.

 

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Tyre rotation

 

Tyre rotation is interchanging tyres from one wheel to another intended to achieve equal tyre wearing. Rotation is necessary due to uneven tyre wearing on different positions on a vehicle.

 

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M+S letters on passanger car tyres

 

If you do not know the meaning of these signs on tyres, don’t worry, it is not completely clear to the biggest European traders, too. The reason is that in EU does not exist legally defined term of winter tyres.

However, ECE rule no. 30 EU directions 92/23 and §36 of German Strassenverkehrs-Zulassungs Ordnung (German traffic rules), states that winter tyres should always have the marking M+S, M&S ili M.S. It means that all tyres marked with these letters, including some summer tyres, can be considered as adequate winter tyres.

Hence, markings M+S do not mean that the tyre is compulsory a winter tyre, it can be a winter or an all weather tyre.

 

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Why winter tyres?

 

Winter tyres are designed to drain water effeciently under the tyre and decrease the risk of aquaplanning. The heat produced in traction between tyres and the ground melts the icy cristal tops creating thin layer of water between tyres and the ground which is slippery. Small holes on the tread surface of winter tyres are designed in such way to drain water effeciently providing better stability of a vehicle on wet roads.

Winter tyres have substantially better coherance and a shorter detention path while braking due to deeper tread grooves. According to testing results made on ice with summer tyres at the speed of 30km/h, the detention path was 68m, and with winter tyres it was 57m which is enough to evade a clash!

Winter tyres are produced from a special mixture with the addition of silica which has better performances at lower temperatures and allows smooth and comfortable ride. In comparison to summer tyres, winter tyres do not harden at low temperatures. It is very important to mention that winter tyres are to be used not only for snow and ice but also for a dry ground with temperature under +7°C.

In many countries the law administers obligatory placement of winter tyres which we can expect in near future.

 

 

Taken from 4gume.com