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About 3o percentof braking distance can be

reduced by tyre choice.

Editorial Dr. Ulrich Hackenberg 2Humble Heroes What Tyres Are Responsible for 2Layer on Layer A Close Look at Composition 4More Than Rubber The Mix Makes the Tyre 6Rolling Out How Old Tyres Can Be Recycled 8Imprint 8

5 percentof fuel can be saved using

low resistance tyres, extra urban.

TyresBetween Good Grip and Smooth Running

VIAVISIONSHAPING THE FUTURE OF MOBILITYVOLKSWAGEN GROUP

NO 07September 2012

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A cars environmental footprintdepends, among other factors,on its tyres. It is our goal toselect the ideal tyre for every carmodel and every engine option,to find the optimal trade-offbetween vehicle safety, fuelconsumption and comfort. On

the following pages VIAVISIONwill demonstrate how compo-nents, new additives and tyrerecycling ensure safety and agood environmental balance.

Happy reading.

Editorial

Tyre manufacturers try to reducerolling friction by constantly

introducing new rubbercompounds into their tyres.

Besides rolling resistance, fuelconsumption is influenced by air

drag and friction as well asinertia. The saving potential of lowrolling resistance tyres is highest at

medium speeds because this iswhen rolling resistance constitutes

the largest part of total driving

resistances. Extra urbanreduction is five percent; low

rolling resistance tyres save fourpercent on average.

Source: Initiative ich & mein auto/dena,German Energy Agency (as of 2010)

Fuel saving through the use of low resistance tyres:(in percent)

When the tyre touches the road,it will be compressed in thearea of the tread. This deforma-tion of the tyre consumesenergy that is lost as rollingresistance in the form of heat.The higher the rolling

resistance is that the tyre hasto overcome, the higherperformance the engine mustprovide that costs fuel.

Sources: Michelin; ADAC (both as of 2012)

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A deep tread ensures greater grip on wet surfaces and also shortens the brakingdistance. Already at tread depths of less than four millimetres, grip lessenssignificantly because the tyres cannot adequately displace the water on the road.In Germany the minimum legal tread depth is 1.6 millimetres. Summer tyresshould however be replaced at a tread depth of three millimetres, winter tyres ata depth of four millimetres. Source: Continental (as of 2012)

At a residual speed of* 34 kilometres per hour,

** 44 kilometres per hour,*** 31 kilometres per hour.

3

07 September 2012 PERFORMANCE

Full tread depth

Increase in braking distance due to reduced tyre tread:(in metres) Volkswagens tyre

pressure monitoringsystem

The driver ensures the correcttyre pressure by driving to thepetrol station and checkingthe pressure with a gauge.Tyre pressure monitoring

systems installed in the vehicletake over this task. Theymonitor the air pressure andshow dangerous pressurechanges with a warning lightor an audible warning.

Volkswagen has two such

systems in its range: thepassive tyre pressure monitorand the active tyre pressuremonitoring system, with or

without position sensing.The tyre pressure monitor is asoftware module in the centralcontrol unit of the vehicle.Using data from the anti-lockbraking system, the circumfer-ence of the tyre is determined,alerting the driver to changes.This system is available for theGolf, Passat and Polo. Active

tyre pressure monitor measu-res pressure and temperatureusing active sensors on the

valves of the tyre and transmitsthe data to the control unit ofthe vehicle. In addition, thetyre pressure monitor withposition sensing shows thedriver which tyre has lostpressure. This active system isinstalled in the Phaeton,

Touareg and Passat.Source: Volkswagen

Increased fuel consumption at decreased air pressure:(in percent)

Three millimetres tread depth

+ 9.5*

1.6 millimetres tread depth

+ 9.5** + 9.1***

+ 8

1.1 bar

+ 4

1.4 bar

+ 2

1.6 bar

+ 1

1.8 barRecommendedair pressure: 2 bar

The right air pressure in the tyre plays animportant role. If it is too low, the tyre can heatup severely during driving, damaging its fabric.Additionally, the higher rolling resistance leadsto higher fuel consumption and abrasion. Thecorrect tyre air pressure is also vital with respect

to safety: a small loss of pressure already leadsto a significantly longer braking distance;stability and grip on wet surfaces decreasesconsiderably. Experts recommend checking thetyre pressure every 14 days and, if the car isheavily loaded, adjusting it accordingly thissaves fuel.

Sources: FOCUS Online; Continental (both as of 2012)

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4

COMPOSITION VIAVISION

Layer on LayerA Close Look at Composition

The predecessors of todays tyres were made of wood, with a covering of

leather or metal to protect against wear. The first Benz motor car stilldrove on wooden wheels but these were already covered with a protec-

tive rubber layer. Several years passed until the tyres were finallyinflated with air. Today a tyre consists of nine different components.Each of these has a specific function to increase driving safety.

Sources: Continental (as of 2011);Goodyear (as of 2009)

7

9

Tyre components:

1 The tread is the outer part of the

tyre, which has direct contactwith the road. It is usually madeof synthetic and natural rubberand is responsible for road gripand water displacement. Thedurability of the tyre, and thus itsmileage, depends on it.

2 The cap ply lies directly underthe tread. It is made of nylonfabric and additionally reinforcesthe tread, making higher speeds

possible.

3 The steel belt gives the tyrestrength and stability. As a resultit keeps its shape when driving,and the rolling resistanceremains low.

4 The body ply is a solid textilestrip which is cut so that thethread runs transversely to thedriving direction.

5 The inner layer of rubber replacesthe pneumatic tyres and innertubes that were formerly usedand makes the tyre airtight.

6 The rubber side wall protectsthe tyre from damage from theoutside.

The bead reinforcement, or

reinforcement strip, consists ofnylon or aramid, a plastic fabric.It supports driving stability andallows accurate steering. Inaddition, it improves roadcondition feedback to the driver.

8 The bead filler, made of syntheticrubber, improves stability andreduces tyre deformation duringcornering. In addition, it contrib-utes to a better steering re-sponse and it improves thesuspension of the tyre, for exam-ple, when driving over a curb.

The steel core provides a tight fiton the rim.

6

4

7

8

9

2

3

5

1

Tread, cap ply and steel belts arepart of the running surface of the

tyre. All other components form thecasing, the structure of the tyre.

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5

07 September 2012 COMPOSITION

Not having to stop on a flat tyre,but simply continuing to thenext workshop this is made

possible by so-called run-flattyres. Reinforced edges let thetyres carry the weight of the

vehicle, even when all the airhas escaped. Up to 150 kilome-tres can still to be covered at amaximum of 80 kilometres perhour. Since the pressure loss inthe tyre while driving may notbe noticed by the driver, an

electronic pressure monitoringsystem is mandatory. Anyonewho decides to drive on run-flattyres, and therefore goes

without a spare tyre saves weightand fuel, however they mustaccept that the run-flat tyres aremuch stiffer and heavier. At lowspeeds, they offer less comfortand cause louder noise thanconventional tyres.

Run-flat tyre

The most important data regarding the tyre is on the label on its edge.

The small combination of numbers and letters contains informationabout the various dimensions and the carrying capacity of the tyre.

Tyre width

Specifies the width of the tyre in millimetres. It ranges from 125 up to 335millimetres.

Height to width ratio

The second number indicates the percentage ratio of height to width ofthe tyres cross section. In a tyre with a height-width ratio of /50 the tyre

section is half as high as it is wide.

Tyre structure

The letter R stands for radial construction, now common, in which thetextile cords of the casing are arranged at right angles to the runningdirection. If there is an additional F behind the R, it is a run-flat tyre.

Rim diameterThe diameter of the rim is measured in inches, and typically rangesfrom ten to twenty inches, corresponding to 25.4 to 50.8 centimetres.

Load index

The load index (abbreviated LI) indicates the maximum load that a tyreat a maximum of 210 kilometres per hour and a given tyre pressure canbear. They range from a load index of 30, corresponding to 106 kilo-grams per tyre, up to a load index of 109, equivalent to 1,030 kilograms.

Speed ratingThe speed symbol or speed rating shows the permissible top speed. F isthe lowest speed at 80 kilometres per hour, Y is the maximum speed of300 kilometres per hour.

Sources: ADAC; Fulda (both as of 2010); Continental (as of 2012)

Side note

Run-flat tyres can carrythe cars weight even when all the

air has escaped, due to theirreinforced side walls.

Sources: ADAC (as of 2010);Bridgestone (as of 2012)

Strong side:

Standard Run-flat

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6

More Than RubberThe Mix Makes the Tyre

When selecting materials, tyre manufacturers are faced with a classicconflict: a tyre should have excellent grip, meaning it holds the road,and at the same time should have as little rolling resistanceand abrasion as possible. If grip is improved by greater elasticity,

abrasion and rolling resistance are consequently increased. And viceversa: reduced rolling resistance due to higher stiffness negativelyimpacts grip. To address this conflict, the tyre consists of more than

just rubber.

MATERIAL VIAVISION

ReinforcementsSteel, nylon, polyester or other plastics servefor reinforcement, for example at the steelbelt or cap ply (see page 5).

SoftenerOils and resins maintain the flexibility of therubber. However they evaporate over theyears, making the tyres hard and brittle.

Chemicals for vulcanisationFor the vulcanisation sulphur and zinc oxideis used, among other chemicals. At thisstage of the tyre manufacturing process therubber is subjected to high pressure for acertain time at specified temperatures, sothe sulphur molecules bond with the rubber.

This way the finished tyre takes its originalshape after deformation, has a highertensile strength and is more resistant toweathering and ageing.

Composition of a standard tyre:(in percent)

30

15

66

2*

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7

07 September 2012 MATERIAL

FillersCarbon black, silica, carbon or chalk can beused as fillers. They maintain the tyresconsistency by reducing abrasion. Previouslycarbon black was used exclusively, todaymainly silica, the salt of silicic acid, is used.Silica is the solution to the trade-off conflictin tyre production (low rolling resistancewith, at the same time, good adhesion), bymaking the rubber harder, while its molecu-lar structure increases grip.

RubberSince the amount of rubber required by thetyre industry cannot only be gleaned fromthe juice of the rubber tree alone, this rawmaterial for tyres is mainly producedsynthetically. The properties of the rubberare temperature-dependent: mixtures thatdrive well at high temperatures can hardenin cold weather. Therefore different types aremixed to achieve the correct properties for

summer and winter tyres.

Oil substituteSynthetic rubber is mainly derived fromcrude oil but this raw material is scarceand expensive. For this reason, some tyremanufacturers make use of other biomate-rials, for example, corn starch and sugarcane. The biomaterial is transformed usingbacteria so that it can serve as the rawmaterial for synthetic rubber. This biorubberstands out due to its low weight and

resistance to heat and weather.

Sources: Continental (as of 2011); Gevo;Bridgestone; LANXESS (all as of 2012)

Pictures (clockwise): BP Europa SE; jakawan_k-Fotolia.com;ThyssenKrupp Steel Europe AG; styf-Fotolia.com; LANXESS

41

*Other.

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8

RECYCLING VIAVISION

Rolling OutHow Old Tyres Can Be Recycled

What actually happens to a tyre if it cannot be used anymore because,

for example, the tread is worn out or the material has become brittle?Every year, more than three million tons of old tyres accumulate in

Europe, 600,000 of them in Germany alone. These old tyres arerecycled in three different ways.

1oopercent of old tyresin Germany arerecycled. 96 percent across

Europe, 85 percent in the USA.Source: Continental (as of 2012)

Sources: Continental; Volkswagen (both as of 2012)

The tyre can be remoulded ifonly the road tread is damagedbut the casing is still usable.The old cover of the tyre ismilled off and replaced by anew one with an unused tyretread. 5.5 percent of all car tyresin Germany are remoulds. The

share for utility vehicles, withtheir significantly larger andheavier tyres, is around 40percent because they cost a lotmore than ordinary car tyres.

Remoulding

After the old tyres are shredded andthe components separated, rubberand textiles as well as metals can befurther processed. The rubber, for

example, is used as a granulate forroad construction and improvessound insulation in tarmac.

Material usage

The concrete industry uses oldtyres as a substitute fuel, savingfossil fuels. They are especiallysuitable for the production of concrete that takes place at temper-

atures up to 1,500 degrees Celsiusbecause of their high energy

content. Additionally, the steel thatis contained within the old tyressubstitutes the required iron ore.

Thermal recycling

Picture:ReifenIhleGmbH

Picture:m

hp-Fotolia.com

Picture:Smileus-Fotol

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Editorial staff

Susanne van den Bergh, Stefanie Huland,Kathi Preppner, Carina Reez, Lena Wilde

Contact: redaktion@viavision.org