The Effect Of Pressure Loss Under Simulated Driving Conditions

Studies of the relationship between tire pressure and rolling resistance have relied on static testing of inflation pressure loss rates (IPLR).  In order to examine the pressure loss and resulting changes in the rolling resistance of tires under conditions that more closely resemble tires when used in service, a new multistep roadwheel test procedure was investigated.  Six tires with known ASTM F1112 IPLR (static) and ISO 28580 rolling resistance (RRC) values were selected in order to develop this Dynamic IPLR test.  Testing consisted of obtaining tire pressure values during operation on a 1.707-meter laboratory roadwheel.  After each incremental operation on the smooth drum, the inflation pressure and resulting RRC values of the six tires were measured. Testing continued until 58,000 kilometers was completed on the roadwheel.  Results are similar for all tires, namely that inflation pressure decreases and rolling resistance increases after each cycle after an initial break-in period which was dependent upon the tire brand.  Dynamic IPLR values were calculated and are higher than IPLR values measured under static conditions at room temperature (ASTM F1112), but not when measured under static conditions at 60^oC.