Friction decrement at high speeds?

[MSI]

The friction decrement with speed is normally associated with wet pavement.
From a discussion from our m-smac user's manual on friction loss with speed:

In general, on wet surfaces, the effective tire-surface friction coefficient decreases with speed and c (card 12:field 7) can be used to simulate the decrease. The effective friction coefficient, used in all SMAC calculations, is computed as:
effective MU = MU0 - MU0 * c * |v|
where :
MU0 =the nominal coefficient of friction,
c =CMU, the coefficient of linear decrement with speed
|v| =the absolute value of the tire speed in inches/sec.

Some manuals for other versions of SMAC have recommended the use of a value of C=0.0003 sec/in. This value should not be used for dry pavement. The use of this value for dry pavement results in the following effective for a 0=0.70:

Speed(MPH), XMU
0, 0.70
20, 0.63
40, 0.55
60, 0.48

For dry pavement applications a reduction in the effective friction coefficient is normally not as apparent as in wet road applications.
Therefore, for dry pavement, normally you should set C=0.0.