The basic labels-letters for tyres

175/70 R 13 82 T

Speed rating index

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

Load range index

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.

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.

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.

Mass distribution on the front and back axis is different depending on vehicle types causing the uneven tyre  wearing. In vehicles with the back haulage, mass distribution is approximately 50:50. In vehicles with the front haulage, differential is placed in front and the front axis is more loaded causing mass distribution approximately 60:40 on behalf of the front axis. It means that front tyres wear faster since they withstand almost twice heavier load than the back tyres, especially taking into account that front tyres endure additional strain while braking. Therefore in front haulage vehicles tyres must rotate more often.

Due to uneven thread depth grooves in front compered to back tyres, braking is worse as well as steering, especially on wet roads. If you do not rotate tyres in time, you will have to replace both front tyres at the same time thus  having always tyres with different thread depth.

Turning of a car causes uneven tyre wearing, front tyres suffer heavier wearing. It is considered that right turnings are sharper than left ones which causes heavier tyre wearing. In countries of right side driving, sidewall of a tyre is worse damaged and worn because it bumps the pavement while parking.

Mechanical problems with a vehicle can be caused by uneven tyre wearing. The wheel which is not centered is pulled by other wheels thus it suffers heavier wearing. If wheels are not balanced or centered, the vehicle will sideslip when you let the steering wheel free. The driver constantly aligns the vehicle and tyres turn which also causes uneven wearing.

Also if the pressure in tyres differs, some are overinflated, other deflated, tyres will not be worn equally. When the pressure is over the recommended, the middle part of the protector suffers serious damage, and when it is less than recommended the outer part of the protector is more damaged. Tyre rotation in that case will not help unless tyre pressure is not as recommended.

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.

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.

Benefits of nitrogen tyre inflation

Recommended tyre pressure and its maintenance by nitrogen

Inadequately inflated tyres are the cause of 90% tyre deformities while driving which can be extremely dangerous sometimes. The benefits achieved by maintenace  regular tyre pressure are following:

   Optimal contact surface between a tyre and the ground

   Less rolling resistance

  Less and equal  tread surface wearing. Poorly inflated tyres are worn faster at outer rims while overinflated suffers damages on central part of tread surface.

   Better steering especially while turning on wet and icy roads

   Economic fuel consumption

Reduced tyre heating during  driving

Tyres inflated by nitrogen heat less than tyres inflated by compressed air. Benefits offered  from this feature of nitrogen are:

   Expended tread surface life. What will the tyre be used depends on the temperature reached during driving. If you drive at speeds near to or higher than the speed rating index marked on the tyre or the load of vehicle is higher than allowed  by load rating index.

   Reduced risk of tyre burst at high speed

Reduced risk of pressure rise

Tyre pressure rises when temperature rises. What will be the pressure rise depends on speed and load of a vehicle. In race tyres, pressure can rise for  50% compared to cold tyres. Nitrogen inflated tyres have considerably less pressure rise with temperature.

Nitrogen prevents corrosion

Corrosion of steel wheel rims, valves and internal wire structure of a tyre is caused by presence of water and  oxigen in the air. Corrosion is prevented by using nitrogen which slightly oxidize.

To conclude,  if you do not check tyre pressure regularly, nitrogen inflation is a good choice  for your tyres. Recommended tyre pressure maintains for a longer period of time, tyre lifetime is for 25% longer, fuel consumption less, better steering, smoother and safer riding. Nitrogen inflated tyres are less heated and reduced risk of explosion while driving at high speed. Benefits are numerous, it is worth trying.

 Taken from 4gume.com