Friction Depends on Following Factors

• Type of pavement (bitumine,earthen material or WBM)

• Roughness of the pavement (textures)

• Condition of the pavement (dry or wet , rough or smooth)

• Condition of the tyre (new with good thread or old worn out thread)

• Speed of vehicle

• Extent of break application (full or partial)

• Load & type of pressure

• Temperature and tyre & pavement

HENCE

Old tyre friction on dry surface > New tyre on dry surface

Old tyre friction on wet surface < New tyre on wet surface

Hence new tyres are more dependable in adverse conditions then the old ones.

• For calculation if stopping distance the longitudinal friction coefficient has to be taken as (0.35-0.40) at f=0.4 saturation available is approx 4 m/sec2
• And transverse friction is to be taken as 0.15