Driving safety…

… a matter of grip

Grip - The tyre is not alone…

The traction performance of a tyre must always be analysed by taking in account all the conditions of use

The final grip potential is a combination of the properties of multiple parameters

The tyre Weather conditions

(temperature, dry, water height, snow, ice, ….) ...

Influent parametersPhysical solicitations

Speed, straight line, curves, braking, slip angle, …

Road surface texture

Macro & micro texture, …

On a dry road surface, rubber tends to « stick »:It’s the adhesion force (10-20% of the grip potential)

… but the tyre is a key factor for the gripGrip comes from the contact between the tyre and the road:

The rubber, through its specific properties, creates the friction potential:

… but the tyre is a key factor for the gripGrip comes from the contact between the tyre and the road:

The rubber, through its specific properties, creates the friction potential:

Its softness enables it to surround the surface texture:It’s the indentation force (80-90% of the grip potential)

2 ways of sorting: • Macro-roughness: size of gravels one can see• Micro-roughness: surface of the gravels, micro-texture (smoothness)

The different road textures types

The different road textures types Grip varies along those roughnesses. On Wet road:

• Adhesion is inhibited by any water molecule / interface• Indentation can be reduced as the roughness of the ground is filled up

with water

1µm to 0.1 mm

0.1mm to 10 mm

Challenge for the tyre:Try to create a dry zone in its contact patch, with maximum adhesion and indentation components

High Safety: How to have grip on wet roads?

#1: Evacuate Water • Architecture : Rounded Contact patch shape

to cleave through the water bank• Tread Design : acts like pipes

to evacuate/store water

#2: Restore Dry contact condition • Lamellas & Block Edges to break through

the residual film of water

Braking test method…

… a matter of grip

Braking Test Method: 80 to 20 km/h with ABS

Distance

Driving speed

90km/h80km/h

20km/h

DsDistance covered

from 80km/h to 20km/h

Tyre manufacturer test:Tyre performance is directly linked to Ds: Braking distance 80-20km/h

full ABS braking power established, tyre employed at its maximal grip

Time of Brake pedal contact:

full ABS braking power deployed

full ABS braking power deployed

Driving safety…

… a matter of grip