Demystifying the coefficient of friction

Understanding the Coefficient of Friction (CoF)

The coefficient of friction is defined as the ratio between the maximum friction force applied by the sole of a shoe and the force pushing the sole against a given surface.

The higher the coefficient of friction, the greater the resistance to sliding. Experts from the SATRA laboratory consider that a CoF of 0.3 allows normal walking on a given surface, while a CoF greater than 1.25 would create a risk of falling because it could cause the foot to stick while walking.

Several factors can influence the result obtained during a coefficient of friction test, including the material used to make the sole and the pattern used on the outsole. 

How is the coefficient of friction of shoes tested?

SATRA TM144 is the preferred testing method for classifying shoes as “non-slip.” For most ROYER products, tests are performed on 2 types of surfaces, namely stainless steel (both wet and dry) and ceramic tiles (wet), but testing can also be done on dry ice and wet ice when necessary, as with our range of products using Vibram Arctic Grip soles. We’ll publish another blog post soon to give a detailed analysis of the coefficient of friction on icy surfaces.

In the laboratory, testing is performed using the SATRA STM 603 device, which is able to reproduce the motions that take place during walking. The device applies a constant vertical force, intended to represent approximately the weight of half the body, to bring the shoe into contact with the surface; then, the shoe and the floor surface are moved horizontally towards each other. The horizontal force acting on the shoe during this movement is then measured, allowing the coefficient of friction to be determined. This test is performed with the shoe completely flat as well as on the heel. 

Finding the right shoe for your foot

As a user, it is essential to consider the intended use of your shoe and the kinds of surfaces it will be used on to determine the most appropriate coefficient of friction for a particular application. By choosing shoes designed with optimal grip and suited to your work environment, you can walk with confidence, knowing you have the traction needed to keep you safe.