Tyres provide the only points of contact between your vehicle and the road. They are therefore essential to active safety and performance.
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The tread of your tyres (the rubber pattern on
their surface) has to transmit all the forces that pass between your
vehicle and the road. Tyres have to support the weight of your vehicle, steer it, transmit drive and braking force, grip the road and even assist your vehicle's suspension. Tyre grip determines the ability of the wheels to follow the road without slipping or skidding. Underinflated, worn or hard tyres reduce stability on bends and can make your vehicle dangerous in the wet and under braking.
Friction and therefore grip at the patch of contact between tyre and road influences:
Understanding the basics of tyre design contributes to your safety in
all driving situations. Tyres are not made from rubber alone. They have
quite a complex internal structure.
Tyre designs differ according to the season of the year for which they are intended. There are three main types including:
These deliver excellent performance and high grip in the dry.
In heavy rain, snow, or particularly cold temperatures, this type of
tyre does not offer the same performance as it does in the dry.
Performance drops on cold road surfaces (below 7°C): at 25 mph,
stopping distance doubles on a snow covered road.
These guarantee excellent performance in winter weather because their structure and tread pattern favour the rapid expulsion of water,
preventing aquaplaning and offering better traction. Winter tyres offer
far shorter stopping distances on snow or ice-covered roads: on a cold
asphalt surface, winter tyres reduce stopping distance from 50 mph by
about 8 metres under emergency braking. Various
European countries have introduced legislation obliging motorists to
equip their vehicles properly for the winter. This legislation also
requires the fitting of winter tyres.
Designed for use in all weather conditions, they guarantee standard performance on any type of road, at any temperature.
The European Union has introduced a new, obligatory tyre labelling system to ensure the diffusion of clear and authoritative information on:
Starting from November 2012, all new tyres sold in the European Union
must be marked with the information needed to evaluate their
EC Regulation 1222/2009 specifies various performance ratings for:
Rolling resistance has to be evaluated for all
tyres sold in Europe. EC Regulation 1222/2009 establishes 7 ratings for
rolling resistance:A: the rating for tyres that offer the greatest saving in fuel consumptionG: the rating for tyres that offer the smallest saving in fuel consumptionThe higher a tyre's rolling resistance, the further its energy rating will be from class A.
This parameter is important for its contribution to reducing CO2
emissions and running costs: the difference between one rating and the
next corresponds to a reduction or increase in fuel consumption of
around 0.1 litre every 100 Km.
The choice of an A rated tyre instead of a G rated one can mean a saving of 6 litres of fuel for every 1,000 kilometres, equivalent to a 7.5% saving in fuel consumption (as measured according to the test parameters established in Regulation EC/1222/2009).
Important! Energy efficiency depends not only on a tyre's physical characteristics but on its inflation pressure too.
Wet grip is a fundamental safety parameter and defines a vehicle's ability to stop rapidly on a wet road surface.In
a wet grip test, a vehicle's brakes are applied on a wet surface
according to procedures established in EC Regulation 1222/2009.
The effective stopping distance is measured and a rating between A
and F assigned, with A corresponding to tyres with the best grip and F
to those with least grip. Ratings D and G are not used for cars. In
safety terms, there may be a difference of 30% in stopping power between
an A rated tyre and a G rated alternative. At a speed of 50 mph, this
is equivalent to a difference of over 18 metres in stopping distance*.
*As measured according to the test methods established in EC Regulation 1222/2009.
This is the external noise caused by the tyres'
rolling during driving as heard from outside the vehicle: the noise
level is measured in decibels (dB).
The label shows a speaker with three sound bars. One
bar indicates a quieter tyre (highest performance) while three bars
indicate those that are less quiet (lower performance).
The markings on tyre sidewalls precisely identify
tyre characteristics. This information is important because each vehicle
can only be fitted with tyres of the size and type specified in the
Owner Handbook.Each number marked on the tyre identifies a
precise physical characteristic. For example, the Owner Handbook may
specify tyres of size 215 65 R 16 95H where:
The date of manufacture (DOT) is also marked on the
side of the tyre. The week and year of production are specified in the
form a four figure code. For example, the code 4712 identifies a tyre
made in week 47 of the year 2012.
Aquaplaning is one of the greatest risks involved in
driving on wet roads. When a vehicle aquaplanes, its tyres start to
float on a cushion of water, immediately losing contact with the asphalt
beneath. Aquaplaning is a dangerous phenomenon,
typically caused by driving at high speed over a very wet road or an
asphalt surface with puddles of water. Under these conditions, the
channels in the tread are no longer able to expel all the water from
under the tyre; a cushion of water forms as a result, causing the tyre
to float over its surface. In most cases, aquaplaning can be avoided by careful driving combined with good, correctly inflated tyres,
since tread patterns are designed to drain large volumes of water in
order to maintain an effective grip. If your vehicle starts to
aquaplane, applying the brakes is useless
because your tyres are no longer in proper contact with the road.
Braking could even cause the vehicle to swerve violently when the first
tyre regains grip, causing you to lose control.
The best thing to do is keep a firm grip on the steering wheel
ready for the moment the tyres regain their grip, while maintaining
directional control for as long as the phenomenon persists. Also,
gradually release pressure on the accelerator pedal, since engine speed
will have increased as soon as the wheels began to float.
In addition to being unsafe, underinflated tyres also increase fuel consumption. Because
they offer greater rolling resistance, they require more energy to
turn, which translates into increased fuel costs. Once fitted to wheels,
tyres inevitably deflate over time. It is therefore important to check tyre pressure regularly and respect the values specified in your vehicle's Owner Handbook. Correctly inflated tyres can save you up to 5%* in fuel costs.* Source: U.S. Environmental Protection Agency (EPA)
Underinflated, worn or hard tyres significantly reduce stability on bends and can make your vehicle dangerous in the wet and under braking Respect the tyre sizes specified in your vehicle's documentation. It is illegal to fit tyres of a size not permitted by your vehicle's registration document. While it is not permitted to fit tyres with a lower speed rating than that of the ones fitted as original equipment, it is permitted to fit tyres with a higher speed rating. You are also allowed to fit your vehicle with winter tyres with a speed rating one letter below that of its summer tyres. Keeping your tyres inflated to the right pressure can save you up to 5%* in fuel. Correct inflation and use of tyres suitable for the season make a major contribution to safety and tyre life. Have your tyres checked regularly by an Authorised Fiat Professional Service Centre. They can also change your tyres if necessary. Their specialist personnel will also be able to recommend the best tyres for your requirements.* Source: U.S. Environmental Protection Agency (EPA)
It is good practice to check your tyre pressure regularly. The correct pressure is specified in your vehicle's Owner Handbook.
Tread depth varies from one type of tyre to another, but its minimum
value is established by law. Tread must be at least 1.6 millimetres deep
across the surface of the tyre.
Cuts and lacerations in the sidewalls of a tyre can be dangerous,
especially if they penetrate to the plies of the structure. Replace the
tyre immediately if you notice this kind of damage.
Dents in the rims can cause vibration in the steering and even lead to the tyre coming off the rim.
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