Snow blower tire chains

Tire load sensitivity describes the behaviour of tires under load. Conventional pneumatic tires do not behave as classical friction theory would suggest. Friction theory says that the maximum horizontal force developed should be proportional to the vertical load on the tire. In practice, the maximum horizontal force Fy that can be generated is proportional, roughly, to the vertical load Fz raised to the power of somewhere between 0.7 and 0.9, typically.

Production car tires typically develop this maximum lateral force at a slip angle of 6-10 degrees, although this angle increases as the vertical load on the tire increases. Milliken, W.F., Milliken, D.L., 1995, “Race Car Vehicle Dynamics”, Society of Automotive Engineers (SAE) Warrendale, PA. page 27. Formula 1 car tires may reach a peak sideforce at 3 degrees Wright P., 2001, “Formula 1 Technology”, Society of Automotive Engineers (SAE) Warrendale, PA.

Example

As an example, here is data extracted from Milliken and Milliken’s “Race Car Vehicle Dynamics”, figure 2.9:

The same sensitivity is typically seen in the longitudinal forces, and combined lateral and longitudinal slip.