Tire slip-angle force measurements on winter surfaces

Tire lateral force data on winter surfaces cannot be obtained with the traditional laboratory test technique of an instrumented tire on a moving belt surface. Furthermore, changing snow and ice conditions can drastically change the tire/surface interaction. In this study the Cold Regions Research and Engineering Laboratory’s (CRREL’s) Instrumented Vehicle (CIV) was used in a unique configuration to measure tire lateral force versus slip-angle data on ice and snow at various temperatures, moisture contents, depths, and densities. The vehicle is instrumented to record longitudinal, lateral, and vertical force at the tire contact patch of each wheel as well as vehicle speed, tire speed, and front tire slip angle. The tests were conducted at the Keweenaw Research Center (KRC) in northern Michigan in February 2005 and March 2006. Tests were conducted on ice, packed snow from 0.50 to 0.58 g/cc, remixed snow depths of 2.5–20.3 cm at 0.43 to 0.48 g/cc and freshly fallen snow with depths of 0.5–17 cm at 0.07 to 0.23 g/cc. Surface air temperatures during testing ranged from −14 to 1.6 °C. The data collected show that peak lateral force and the shape of the lateral force versus slip-angle curve are related to snow properties and depths.