Tire Deflection Influence on Rear-Axle Torque

Data were obtained on an 18-wheel western-type log truck with central tire inflation (CTI) and carrying a highway load. Operating on grades of 20 and 25 percent, drive shaft torque was monitored to quantify stress levels on the drive train while varying tire deflection. Information is provided on the limits of additional traction to be gained through the use of tire deflection when operating on steep terrain-without excessive tire slip or vehicle maintenance.

Using the proper tire deflection (based on speed and load) appears feasible through the use of CTI systems. Benefits have been seen in reduced vehicular damage to forest roads and increased tire life plus improved traction on some road surface types because of the increased tire tread length.