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Workshop wet braking
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Workshop wet braking

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Transcript

  • 1. Driving safety…… a matter of grip
  • 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
  • 8. Braking test method…… a matter of grip
  • 9. Braking Test Method: 80 to 20 km/h with ABSDriving 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
  • 10. Driving safety…… a matter of grip