PIRELLI TYRE KNOWLEDGE
Over one hundred years' experience of tyre technology has enabled Pirelli to combine in their products maximum levels of security, longevity, comfort and attention to the environment.
Each Pirelli tyre provides not only performance but also a "feel for the road" and a communication with the driver, allowing a better understanding of the vehicle's performance.
We recommend this section if you want to become familiar with the world of car tyres.
In addition to the Tyre Size Designation a tyre may be identified by a Service Description consisting of a Load Index (or two in the case of single/dual fitment) and a Speed Symbol.
The Speed Symbol indicates the maximum speed at which the tyre can carry a load corresponding to its Load Index (except for loads at speed above 210 Km/h) under service conditions specified by the tyre manufacturer.
The Load Index is a numerical code associated with the maximum load a tyre can carry (except for loads at speeds above 210 Km/h) at a speed indicated its Speed Symbol under service conditions specified by the tyre manufacturer.
YOUR SAFETY ON THE ROAD
Observe the rules of the highway code, always be careful and show respect for other drivers. Here is some good advice for driving safely, saving mechanics’ fees, tyres and fuel.
For fans of sports driving only one thought is needed: the road is not the racetrack.
That said, here is some useful advice from the point of view of road safety.
One of the greatest risks of driving in the wet is aquaplaning: how can you counter this phenomenon?
Aquaplaning leads to “floating” of the tyre and immediate loss of grip.
It is a dangerous situation which is typically created by tackling very wet stretches of road or large puddles of water, created by bad road surface drainage, at speed.
At these times, the grooves of the tread don’t manage to expel the water under the tyre and, in practice, you can suddenly find the car “floating”.
With careful driving and tyres which are not worn and are correctly inflated this danger can, on most occasions, be avoided, since treads are designed to drain the greatest possible quantity of water to ensure the best possible adherence.
Now that we’ve clarified the concept of aquaplaning here is some advice on how to cope with this situation.
Braking is no use because the car is floating and moreover there is also the risk, as soon as the tyres grip again, that the car may swerve suddenly making you lose control completely.
The best thing to do is keep a firm grip on the steering wheel to prepare for "regripping" trying to keep the correct steering direction for the entire duration of the phenomenon and take your foot gradually off the accelerator pedal given that the engine revs increase rapidly as soon as the car starts floating.
The first thing: without chains or winter tyres you won’t manage to go anywhere.
The car will have no traction and on braking will be uncontrollable.
Observe the rules of the road scrupulously and be tolerant of drivers in difficulty who are going slower than you.
Increase the distance between your car and the one in front.
To reduce the risk of sliding while going uphill you can use a higher gear than you would use normally in the dry.
When driving avoid sharp acceleration, sudden steering action or braking, to minimise loss of traction on snow or ice.
For optimum performance and safety, it is essential for all four tyres to be the same.
Always use four winter tyres of the same brand, and with the same construction features.
Fit tyres of the same size on the same axle, with the same characteristics of use, tread pattern and conditions of wear.
The use of studded tyres, where permitted, must be extended to all four wheels.
Consult the vehicle handbook for the correct load capacity and speed rating of the tyres to be used.
Inflation pressures must be checked regularly and carried out when the tyres are cold.
If necessary correct the pressure, again when the tyre is cold.
Keep to the pressures indicated by the vehicle manufacturer.
Note, pressures change in relation to the external temperature: a pressure of 2.0 bar measured at +20°C decreases to 1.74 bar at -5°C and falls to 1.59 bar when the temperature is at -20°C (a change of 20%).
Pay attention to the speed limit indicated by the rating on the tyre sidewall.
Optionally, the car may be equipped with tyres of a lower rating than that prescribed, adjusting the speed.
In this case, the European regulations state that the reduction in speed must be indicated on an adhesive label placed inside the car (on the windscreen or dashboard so that it’s always visible to the driver).
The performance of winter tyres remains effective down to a tread depth of 4mm. Below this level they are no longer adequate for winter use but can be used as summer tyres down to the main tread minimum legal limit, set at 1.6mm.
When winter tyres are not being used, they should preferably be kept on wheel rims and inflated, and the pressures checked regularly. If stored without rims, they must be stacked on their sides no more than four per stack so that they are not deformed by the weight.
Rotate winter tyres in the right direction every 10,000/12,000 km.
"Green Performance" technology means fuel consumption could be reduced and environmental impact limited. But a lot depends on your driving habits. Here is some practical advice on how to make the most of the money saving opportunities presented by Pirelli “Green Performance” products.
Everyone knows that… you don’t brake on bends. And yet – pay attention observing the drivers in front of you – practically everyone comes into bends braking, before “letting go” of the pedal when they reach the centre of the bend. And everyone feels that they are perfect drivers since “you don’t brake on bends”.
It’s a shame that all the stage of establishing the trajectory has occurred with the brakes on.
Driving this way subjects the tyres – above all the front ones – to a double exertion: maintaining the trajectory set and – in addition – resisting the force of the braking system.
All in a play of forces that can also endanger the stability of the car (and therefore the roadholding).
For this reason it is fundamental to brake sooner, slow down in time and – above all – brake as much as possible with the wheels straight. Doing it this way takes advantage of the maximum adherence possible offered by the tyre before steering.
Safe and successful off-roading is a combination of knowledge and skill. Understanding specific techniques for different conditions and realising the capabilities and limitations of your vehicle are critical, but the final factor is the tyres on your vehicle.
Tyres can often make the difference between getting out of a tough situation or getting stuck.
The following information is designed to ensure that you get the maximum performance from your Pirelli tyres.
If in doubt, always survey your chosen route on foot. In mud or other difficult conditions move off slowly and avoid spinning the wheels.
Undue wheel spinning will cause the vehicle to slip and will fill the tyre treads with mud.
When approaching soft muddy ground build up speed in low ratio 2nd or 3rd, trying not to spin the wheels by extreme acceleration. Go too fast and you risk bouncing and losing control, too slow and you will loose momentum.
In severe mud the most difficult situations are where the ground has rutted channels and axle deep pits.
Try to straddle the ruts if they are too deep to drive in – this will avoid dragging the diffs through the mud, which will reduce momentum and probably leave your vehicle stuck.
Always try to maintain a steady momentum.
When driving in ruts, vary the accelerator and move the steering wheel from side to side- this allows the lugs on the shoulders of the tyres to grip and bite into the sides of the ruts.
Never try to steer out of the ruts, let the steering wheel find its own way.
Whenever possible, check you wheel arches to make sure that they are not clogged with mud, this clogging will stop the tyres from cleaning the mud from their treads.
For most types of off-road driving it is possible to maintain your normal road pressures. However, in severe conditions It is permissible to lower pressures to increase the tyre footprint and flotation ability.
NB: Never use the tyre pressures below 16psi. Re-inflate the tyres as soon as possible. On route to the service point,drive slowly, and under no circumstances exceed 50mph.
In light snow conditions the tyres will break through the crust and grip on the surface below.
Use high range ratio and avoid revving the engine, go into low range and use a very light throttle, this will encourage the tyres to bite and grip rather than slip.
In very severe conditions it may be necessary to fit chains.
For most types of off-road driving it is possible to maintain your normal road pressures. However, in severe conditions It is permissible to lower pressures to increase the tyre footprint and flotation ability.
NB: Never use the tyre pressures below 16psi. Re-inflate the tyres as soon as possible. On route to the service point,drive slowly, and under no circumstances exceed 50mph.
The skill in tackling rock conditions is to keep to the high ground wherever possible in order to avoid damage to the diffs, transmission or skidplates.
Torque is more important than power in climbing rock slopes, thus first or second gear in low range is best.
Use light throttle to prevent tyre slipping.
For most types of off-road driving it is possible to maintain your normal road pressures. However, in severe conditions It is permissible to lower pressures to increase the tyre footprint and flotation ability.
NB: Never use the tyre pressures below 16psi. Re-inflate the tyres as soon as possible. On route to the service point,drive slowly, and under no circumstances exceed 50mph.
For loose sand select high range four wheel drive – this will maintain speed, if, however the vehicle bogs down, move into low range.
Soft, loose sand is traction sapping and requires continual momentum, often using full throttle.
For most types of off-road driving it is possible to maintain your normal road pressures. However, in severe conditions It is permissible to lower pressures to increase the tyre footprint and flotation ability.
NB: Never use the tyre pressures below 16psi. Re-inflate the tyres as soon as possible. On route to the service point,drive slowly, and under no circumstances exceed 50mph.
When negotiating water it is important that your electrical system is protected.
Silicon based grease on vulnerable items is a good idea.
It is absolutely vital that your air intake will be clear of the water.
Ingress into the engine is terminal and expensive.
Before tackling a water crossing it is critical to survey the course.
Consider:
• The river flow, fast flowing means clean silt-free water. Slow moving may mean soft deep silt.
• Check the depth of water and any silt with a spade or similar. Also check for holes or large rocks which may impede your progress.
• Look closely at the entry and exit banks, bear in mind on exit you will have little momentum.
• When entering the water select low 2nd gear.
Creating a bow wave means the water in front of the vehicle is deeper but a trough is created behind the wave, i.e. in the engine bay.
If you go too fast the bow wave will break over the bonnet losing the trough effect in the engine bay.
When clear of water always drive a short distance with the footbrake lightly depressed to restore braking efficiency.
Check your radiator is clear of mud and leaves, and of course check for damage to your tyres, as you will not have been able to see any potential damaging underwater obstacles.
For most types of off-road driving it is possible to maintain your normal road pressures. However, in severe conditions It is permissible to lower pressures to increase the tyre footprint and flotation ability.
NB: Never use the tyre pressures below 16psi. Re-inflate the tyres as soon as possible. On route to the service point,drive slowly, and under no circumstances exceed 50mph.
TYRES LONG LIFE
For your safety it is important to check your tyres regularly, at least once a month. Look for signs of damage or uneven wear because improper inflation pressures, misalignment, improper balance, or suspension malfunctions can affect the overall performance of your Pirelli tyre and endanger your safety. Always ask your nearest Pirelli tyre dealer for a check and assistance. Tyres are the only point of contact between your car and the road: so keep them in good shape.
The correct maintenance of your tyres is a priceless operation.
Air is totally free and correct inflation pressure is the main secret for a longer 'lifetime' for your tyres.
Insufficient inflation pressure is the main cause of tyre damage.
Extended lifetime and, as a result, excellent performance for a longer period of time, means concrete economic benefits, due to savings in tyre replacement costs and lower fuel consumption.
Correct inflation pressure also improves vehicle manoeuvrability, reducing the 'braking distance'.
A monthly check up is sufficient to keep the tyres at the correct inflation pressure.
It is a quick, yet fundamental way to control the health of your tyres and is important for your driving safety.
Check the inflation pressure on 'cold' tyres. Here are the steps to follow:
Performance and driving safety are two key elements for Pirelli, that’s why we would like to share with you some small actions that will help you drive in total peace of mind and safety.
Tyre rotation is a simple and effective way to prolong the useful life of tyres by achieving more uniform wear.
PERFORMANCE, SAFETY, PEACE OF MIND
Run Flat tyres mean safety.
They provide greater control of your car in emergency conditions and allow you to continue driving safely even during a rapid loss of inflation pressure.
With Run Flat, you will retain mobility in the event of a puncture.
So, if your tyre is punctured, even in pouring rain, the Pirelli Self-Supporting Run Flat means you don't have to bother with the spare.
Instead, you can continue driving for a limited period.
To ensure maximum safety during an emergency situation, the Run Flat tyre must maintain certain speed and distance parameters (80km/h for 80km or 50mph for 50 miles).
Due to these restrictions, it's imperative that motorists be notified when a loss in tyre pressure occurs, and therefore the vehicle must be equipped with a TPMS (Tyre Pressure Monitoring System) to detect and signal tyre pressure changes.
OPERATING REQUIREMENT
Run Flat tyres have been developed based on the specifications of the vehicles on which they are mounted.
Accordingly, Run Flat tyres may only be mounted on vehicles specifically manufactured to accommodate Run Flat tyres.
Run Flat tyres must be mounted in conjunction with a functional Tyre Pressure Monitoring System (TPMS).
The mounting of tyres and installation of the TPMS should be carried out by a specialised dealer.
Pirelli certifies that after pressure loss, Run Flat tyres can continue to run for 80km (50 miles) at a maximum speed of 80km/h (50 mph).
Always refer to the vehicle owner's manual for specific safety and operating information relating to the vehicle.
After the low pressure warning is shown, the condition of the remaining tyres and the TPMS should be checked immediately by a specialised dealer.
A tyre should always be changed and not repaired after a loss of pressure, as it is not always possible to establish the time and conditions under which the tyre has been used with insufficient inflation pressure.
Damaged Run Flat tyres, or Run Flat tyres that have experienced a loss of pressure should be replaced immediately with another Run Flat tyre of identical size and service description (Load Index and Speed Code).
Pirelli recommends that a tyre of a different type, or which contains a different load index or speed code, should never be mounted on the same vehicle.
After a loss of pressure, the rims should be inspected to ensure they haven't been damaged.
Damaged or deformed rims should always be replaced prior to mounting a new Run Flat tyre.
Pirelli recommends the use of Extended Hump rims (EH2), which reduce the risk of bead unseating in case of loss of pressure.
Yes it is possible, although Pirelli strongly recommends that EH2 rims be used because they guarantee improved retention of the tyre bead down to zero inflation pressure. In the event of run flat operation at zero pressure with H2 rims, provided that a Pirelli self-supporting run flat tyre is used in conjunction with a Tyre Pressure Monitoring System (TPMS) or air pressure warning system, the tyre will maintain its run flat characteristics. A TPMS is absolutely necessary to alert the driver that the tyre has lost pressure.
Standard tyres can be fitted to EH2 rims but they will not have run flat features.
Pirelli does not recommend mixing run flat tyres and standard tyres on the same vehicle, even if paired in axle sets.
If you have a puncture, the run flat tyres are designed to permit you to reach a tyre dealer where you can have the tyre checked and replaced if necessary with another run flat tyre.
In exceptional and emergency circumstances a normal tyre with identical dimensions, load index and speed code can be fitted for a very limited period and distance.
It must be noted that standard tyres do not have the same run flat characteristics as the other tyres on your vehicle and must be removed at the earliest opportunity.
Yes, but Pirelli recommends that in a run flat condition you should not exceed 80km (50 miles) at a maximum speed of 80km/h (50 mph).
Pirelli strongly recommends that the different tyre brands should be fitted in axle sets and the tyre pressure monitoring system must be controlled to make sure that the pressure settings are compatible.
Run Flat tyres have been developed based on the specifications of the vehicles on which they are mounted.
Accordingly, Run Flat tyres may only be mounted on vehicles specifically manufactured to accommodate Run Flat tyres, therefore you must contact the vehicle manufacturer if you are in doubt.
No, for safety reasons, Pirelli chooses not to recommend the repair of self-supporting run flat tyres.
A self-supporting run flat tyre should always be changed and not repaired after a loss of pressure because it is not always possible to establish the time and conditions under which the tyre has been used with insufficient inflation pressure.
Yes.
No. After a puncture you can only travel 80km (50 miles) at a maximum speed of 80km/h (50mph), following which the tyre must be replaced.
Provided the vehicle is operated within restricted run flat speed of 80km/h (50 mph), handling is only slightly impaired due to reduced cornering force.
Aquaplaning and braking remain almost the same.
It is recommended that you avoid sharp driving manoeuvres if a tyre is completely deflated, especially if the tyres are fitted to H2 standard rims.
No. The maximum condition guaranteed by Pirelli is 80km (50 miles) at zero pressure at a speed not exceeding 80km/h (50mph).
For vehicles fitted with Pirelli self-supporting Run Flat tyres as original equipment, the tyre manufacturer's recommendations indicated in the owners manual apply.
There are a range of tyre pressure monitoring systems (TPMS) available so you should consult the vehicle manufacturer if you require a specific explanation.
Basically there are two types of system, indirect systems use the fact that reduced air pressure causes the wheel to rotate at a slower speed and when they detect this difference send a warning to the driver.
Direct systems directly control tyre pressure against pre-set values and send a warning when actual pressure falls below set values.
which appears on the sidewall of the tyre. On tyres specifically homologated for BMW vehicles there are also the letters RSC which stand for Run Flat System Component.
Pirelli guarantee a general maximum distance of 80km for all self-supporting run flat tyres.
Vehicle manufacturers conduct their own tests based on specific vehicle models, taking into consideration vehicle weight and characteristics and can decide together with the tyre manufacturer can suggest an increased distance for that specific vehicle.
For vehicles fitted with Pirelli self-supporting Run Flat tyres as original equipment, the tyre manufacturer's recommendations indicated in the owners manual apply.
Pirelli introduces on the market its new “Seal Inside Technology”, the new concept of extended mobility to safely drive your cars in the event of a puncture.
Seal Inside (S.I.) is a new tyre construction technology that allows you to drive on without losing air pressure even after the tyre has been punctured by an external object, covering almost 85% of the possible accidental causes of pressure loss*.
The Seal Inside logo will be used to identify all Pirelli products featuring this new technology.
The logo (in black) is also on the tyre sidewall.
* The Seal Inside is effective for the majority of the punctures apart from the ones that are compromising the integrity of the tyre
Inside the tyre, in the area corresponding to the tread pattern, a sealing layer material tightly blocks every possible air leakage in case of a puncture that passes through the carcass with or without an external object still present.
The Seal Inside deals immediately with the hole and its fast and effective action, in most cases, does not make the driver realize that the tyre has been punctured.
In the event of a puncture, the sealant allows the driver to continue driving – not having to stop the vehicle for an immediate replacement of the tyre – until it can be replaced.
The sealant does not guarantee permanent repair of the tyre caused by a puncture.
For this reason Pirelli recommends that drivers regularly monitor the tyres in order to identify punctures that are sealed, or the presence of nails or screws on the tread pattern.
In such a situation, it is necessary to go to a specialized tyre dealer who can identify the puncture area and remove the object that caused it.
The tyre dealer has to subsequently evaluate the extent of the damage and decide if the tyre can be repaired or not.
Seal Inside tyres can significantly reduce the chance of having a flat tyre but, unlike run flat tyres, are not designed to be driven under inflated or in a flat condition.
In terms of mounting, removing and balancing there are no differences between Seal Inside and standard tyres.
Pirelli tyres with Seal Inside technology do not need dedicated rims and for this reason can be mounted on the same standard rims used for standard tyres.
Seal Inside tyres should be stored in the same conditions recommended for standard tyres.
Premise: examination of a damaged tyre and execution of a proper repair are the responsibilities only of a specialized tyre dealer. Pirelli does not assume any liability for operations performed by third parties.
To perform the repair of a tyre with Seal Inside technology it is necessary to remove the layer of sealant in the puncture area within the tyre until you reach the impermeable butyl layer, for an area with the same size as the repair patch to be applied; after removing the sealant the repair operation is equivalent to that of a standard tubeless tyre.
As is evident, this operation to remove the sealant from the puncture area inevitably means that the treated area loses the special technical feature of Seal Inside.
Within a product line there is no difference in terms of driving performance (rolling resistance, comfort, noise, dry and wet performance) between a Seal Inside tyre and a standard tyre.
The Seal Inside Technology does not need dedicated rims and TPMS (Tyre Pressure Monitoring System) to be used safely on a vehicle; it can be used on any kind of vehicle depending on the tyre size.
DISCOVER THE TYRE MARKINGS
In addition to the tyre size and the service description, on the tyre sidewall there are several different inscriptions: let's have a look at some of them.
This example shows a typical tubeless radial tyre.
For all asymmetric products it is important to fit the tyre on the rim in the correct position.
In fact asymmetric tread pattern designs are developed to offer the best performance considering the different behaviours of the external and internal areas of the tread design.
DOT (Department Of Transportation) is a legal marking required in many countries in order to sell the tyres.
DOT means the tyres meet or exceed the Department of Transportation’s safety standards.
1) Means tyre meets or exceeds Department of Transportation safety standards
2) Manufacturer and Plant Code Number (Assigned by DOT)
3) Tyre Size Code Number
4) Group of Optional Symbols for the Manufacturer ( To identify the brand or other significant characteristics of the tyre)
5) Date of manufacture
When a tyre bears the ECE symbol, this means it is ECE certified and approved to meet ECE standards for physical dimensions, branding requirements and high speed endurance regulations.
The marking is made up of the letter E and a number representing the country releasing the approval sheet, followed by a unique number combination for each product.
When a tyre bears the European Noise Approved number this means it is compliant with Directive 2001/43/EC, respecting the new noise emission levels set for the European countries.
UTQG is a standard defined by the DOT of the USA for grading the performances of tyres in the areas of TREADWEAR, TRACTION and TEMPERATURE RESISTANCE. It applies only to car tyres with a rim diameter of 13" and larger, but not to winter tyres.
TREADWEAR: The treadwear grade is a comparative rating based on the wear rate of the tyre when tested under controlled conditions on a specified government test course.
For example, a tyre graded 150 would wear one and one-half times as well on the government course as a tyre graded 100.
The relative performance of tyres depends upon the actual conditions of their use, however, and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics and climate.
TRACTION: The traction grades, from highest to lowest, are AA, A, B, and C. These grades represent the tyre's ability to stop on wet roads as measured under controlled conditions on specified government test surfaces of asphalt and concrete.
A tyre marked C may have poor traction performance. Caution: the traction grade assigned to the tyre is based on straight-ahead braking traction tests, and does not include acceleration, cornering, aquaplaning, or peak traction characteristics.
TEMPERATURE: The temperature grades are A (the highest), B, and C, representing the tyre's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tyre to degenerate and reduce tyre life, and excessive temperature can lead to sudden tyre failure.
Grade C corresponds to a level of performance which all passenger car tyres must meet under the Federal Motor Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law.
Caution: the temperature grade for this tyre is established for a tyre that is properly inflated and not overloaded. Excessive speed, under inflated tyres, or excessive loads, either separately or in combination can cause heat build-up and possible tyre failure.
TWI is an important safety feature that easily allows how much tread is left on the tyre to be verified.
Narrow bars of rubber are moulded at a height of 1.6 mm (2/32”) across the bottom of the tread grooves. When the tread wears down to these bars, the tyre should be replaced.
Winter tyres, also called snow, cold weather or thermal tyres, and identified by the branding M+S (Mud&Snow) on the side of the tyres together with the drawing of a mountain with a snowflake.
Legally the M+S marking alone is sufficient to identify a winter tyre, but the tyre industry has adopted the snowflake marking to differentiate real winter tyres (M+S and snowflake) from all-season tyres (only M+S).
The Tyre Label is a mark for motor vehicle tyres. Manufacturers of tyres for cars, light and heavy trucks must specify fuel consumption, wet grip and noise classification of the product by means of a sticker or a label starting in November 2012.
This information must also be included in the technical promotional materials. The tyre label will use a classification from the best (green category "A") to the worst performance (red category "G” for Car and “F” for truck).
This initiative results from a proposal by the EU Commission in 2008 and it is part of the Energy Efficiency Action Plan, designed to improve the energy performance of products, buildings and services to reduce energy consumption by 20% until 2020.
(Source: European Commission)
FOR ADDITIONAL INFORMATION SEE ALSO:
European Commission for Energy >
WIKIPEDIA >
Pirelli, as well the entire tyre industry, welcomes the introduction of the tyre label as a good tool to help the end-users in collecting some essential information when choosing new tyres. But the tyre label cannot substitute the wide range of informations offered by the tests performed by specialised magazines. Trustworthy, independent and reliable evaluations of tyre’s performances. Pirelli would like to remind to all end-users that the overall value of the tyre cannot be judged only by the rolling resistance, the wet braking and the external noise values; there are several additional elements (handling (wet and dry), aquaplaning, high speed behaviour, dry braking, wear, snow performance for winter tyres, ...) that have to be considered in order to choose the best product fitting your needs.
The EU Tyre Labelling Regulation 1222/2009 will provide standardised informations on three tyre performance attribute:
The Regulation requires that all the tyres produced after June 2012 and on sale in the EU after November 2012 will carry a sticker or have a label in their close proximity to be shown to the end user before purchasing(*).
The label is intended to give end users some essential information to help them when choosing new tyres.
(*) This information needs to be provided concerning passenger car tyres, light truck tyres and heavy duty vehicle tyres.
Rolling Restistance is a force acting opposite to the travel direction when the tyre is rolling.
Considering that tyres contribute up to 20% of the overall fuel consumption for a car and up to 35% for a truck, it is important to reach low Rolling Resistance values.
Let’s understand how it works: due to the vehicle load, the tyre is deformed in the contact area with the road surface dissipating energy in form of heat. The higher deformations, the higher the rolling resistance and consequently more fuel consumption and CO2 emissions.
In the EU tyre Regulation label, rolling resistance is expressed in grades, ranging from A (best grading) to F for industrial vehicles and G for cars (worst grading).
The difference between each grade means a reduction or increase in fuel consumption of between 2.5% - 4.5% for a car and 5%-8% for a Truck. For a car that could be also roughly expressed in terms of 0.1l/100km.
Wet grip is one of the most important safety characteristic of a tyre. Excellent grip on wet means shorter braking distances when driving in rainy weather.
There are other important parameters which are relevant for safety but wet grip was chosen as the most representative situation in order to compare different tyres.
For a car the difference between each grade means an increase or decrease in stopping distance of roughly 3 and 6 meters when braking from 80km/h.
Traffic noise is a relevant environmental issue determined by several factors such as:
Traffic intensity
Vehicle type
Driving style
Tyre-Road interaction
The value indicated in the label is not the internal that the driver will perceive while driving, but the external one, that is contributing to acoustic pollution.
It is expressed in decibel (dB) and split in 3 cathegories:
1 black sound wave = 3dB less than the future tighter European limit. 2 black sound waves = already compliant with the future European limit. 3 black sound waves = compliant with the current European limit.
The more black bars shown on the label, the louder the tyre.
The rules apply only to passenger car tyres (C1), light truck tyres (C2) and heavy duty vehicle tyres (C3).
The following categories are excluded from the scope:
•Retreaded tyres
•Professional Off Road tyres
•Racing tyres
•Studded tyres (studdable tyres if supplied without studs are covered)
•Temporary –use spare tyres
•Tyres designed to be fitted on vehicles registered for the first time before 1 October 1990
•Tyres whose speed rating is less than 80 Km/h
•Tyres whose nominal rim diameter does not exceed 254 mm or is 635 mm or more
RR is a force acting opposite to the travel direction if a tyre is rolling.
Due to the vehicle load, the tyre is deformed in the contact area with the road surface.
This deformation induces internal losses, same as a rubber ball falling down that does not rebound as high as it was launched.
Tyre RR can be expressed as a Force (Newton) or as a Coefficient (RRC).
The rolling resistance coefficient is defined as RR force (N) divided by the tyre load. The advantage of the coefficient is that it allows easier comparison of tyres designed to be fitted on different cars.
The vehicle engine has to provide a force to compensate RR.
This consumes some fuel and so contributes to the vehicle fuel consumption.
As a rule of thumb, reducing RR by 6% decreases fuel consumption by 1% for passenger cars.
Many other factors contribute to vehicle fuel consumption:
Aerodynamics, vehicle weight, type of engine, auxiliary systems like air-condition, slope of the road, personal driving style, tyre pressure level, accelerations or general traffic conditions.
There are many different tyre characteristics that affect tyre RR. Adjusting the RR can be done by modifying certain of these parameters, but some of them can also have a negative impact on wet grip.
The tyre development engineer must use the right tools in the right amount to achieve the optimum balance for RR and wet grip.
If tyre RR limits are lowered too far, the required tradeoffs could adversely affect the wet grip performance.
Wet grip refers to the safety performance of tyres:
it reflects the capacity of a tyre to brake on a wet road.
There are other parameters which are relevant for safety (e.g. road holding ability, directional control, deceleration ability on wet and dry surfaces at higher speed and aquaplaning behaviour) but wet grip was chosen as the most representative situation of reduced adherence in Europe.
A limit is the minimum acceptable performance level for a tyre to be authorized on the European market;
A grading will give the performance level under defined testing conditions of the tyre on its rolling resistance, its braking on wet surface and its external rolling noise.
It is the responsibility of the national market surveillance authorities to assess the conformity of the declared grading values.
The procedures for verification are detailed under Annex IV of the regulation
POR tyres are specially designed to reach exceptional adherence performances in poor conditions and in all terrain, which does not allow them to fulfil regulatory thresholds and significant grading levels.
There are plans to introduce labelling requirements to retreads; however this will be decided after an impact assessment is performed by the Commission. The Commission shall present the result of this assessment by no later than March 2016.
The European Commission shall start work to develop a harmonised fuel saving calculator which could eventually be posted on each manufacturers’ websites, to calculate fuel savings and compare products
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