2. Grip - The tyre is not alone…
The final grip potential is a combination of the properties of multiple parameters
The traction performance of a tyre must always be analysed by taking
in account all the conditions of use
The tyre Weather conditions
(temperature, dry, water
height, snow, ice, ….) ...
Influent
Physical solicitations parameters Road surface texture
Speed, straight line, curves, Macro & micro
braking, slip angle, … texture, …
3. … but the tyre is a key factor for the grip
Grip comes from the contact between the tyre and the road:
The rubber, through its specific properties, creates the friction potential:
On a dry road surface, rubber
tends to « stick »:
It’s the adhesion force
(10-20% of the grip potential)
4. … but the tyre is a key factor for the grip
Grip 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)
5. The different road textures types
2 ways of sorting:
• Macro-roughness: size of gravels one can see
• Micro-roughness: surface of the gravels, micro-texture (smoothness)
6. 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
0.1mm to 10 mm
1µm to
0.1 mm
7. High Safety: How to have grip on wet roads?
Challenge for the tyre:
Try to create a dry zone in its contact patch, with maximum adhesion and indentation components
#1: Evacuate Water #2: Restore Dry contact condition
• Architecture : Rounded Contact patch shape • Lamellas & Block Edges to break through
to cleave through the water bank the residual film of water
• Tread Design : acts like pipes
to evacuate/store water
9. Braking Test Method: 80 to 20 km/h with ABS
Driving speed Tyre manufacturer test:
90km/h Tyre performance is directly linked
80km/h to Ds: Braking distance 80-20km/h
full ABS braking power established,
tyre employed at its maximal grip
20km/h
Distance
Time of Brake Ds
pedal contact: Distance covered
from 80km/h to 20km/h
full ABS braking full ABS braking
power deployed power deployed
