Friction Statistics and Stopping Distance Calculator Link

How fast can you take that corner? How quick can you stop? It depends on the road surface, and one riding skill to develop is the ability to judge the road surface as we approach a corner or come through an intersection where we may need to stop quickly. Following are some measurements of coefficients of friction for various surfaces to guide our thoughts. These first friction coefficient estimates are motorcycle-specific from the Master Strategy Group:

Concrete 0.55-1.2
Concrete (wet) 0.44-0.9
Asphalt 0.5-0.9
Asphalt (wet) 0.4-0.7
Gravel 0.4-0.8
Ice 0.1-0.25
Snow 0.1-0.55

Here is another estimate, taken from an engineering text on rubber/asphalt and rubber/concrete coefficients:

Asphalt 0.5 - 0.8
Asphalt (wet) 0.25 - 0.75
Concrete 0.6 - 0.85
Concrete (wet) 0.45 - 0.75

Not like we are going to do calculations on the road, but it is useful to see how friction varies on different surfaces. We can see that wet surfaces lose roughly 20% of their grip, and that concrete is about 20% stickier than asphalt. We can see that wet surfaces have pretty wide variations, and roughly the same grip as gravel. For a more practical application, and a cool little utility that shows other variables in motorcycle stopping distances, take a look at the Motorcycle Stopping Distance Calculator.