ABSTRACT
The slip ratio is frequently presented as a percentage, λ(%)=100λ, as in Figure 2. For reasons that may include tire flexibility, tension and torsion of the tread within the
contact patch, and the continual replacement of material within the tire’s contact patch, the complex nature of the tire’s contact with the road within the contact patch means that the coefficient of friction, here represented by µB, does not immediately jump from its static to its dynamic value, as illustrated in Figure 2 [7]. That portion of each curve between λ=0 and the maximum, except for curve 4, may be considered a stable region, in that initial braking causes the friction coefficient to increase so that increased brake pressure within this region is effective in reducing vehicle velocity. The region beyond the maximum in µB may be considered a region of instability, because, except for curve 4, increased brake pressure to further slow wheel rotation becomes increasingly ineffective in slowing the vehicle itself due to a decreasing friction coefficient. Returning to curve 4, its local maximum is also followed by a region of instability, but that region is followed by a stable region caused by the build up of snow in front of the wheel as its rotation slows.
