Figure 2 shows the variation of the inflation pressure and the ISO 28580 rolling resistance force during the dynamic IPLR test for two samples of a selected tire design.
The method explained before for the static IPLR calculation can be employed to calculate the dynamic IPLR using the SmarTire pressure and temperature data.
This dynamic IPLR test does not simulate the tread wear effects.
In order to determine how this compares to the energy losses due to inflation pressure loss during operation, a stepwise tread wear IPLR test similar to the dynamic IPLR test is presented.
Figure 3 shows an example of a drive file used in the tread wear IPLR test.
Tire preparation for the tread wear IPLR test was similar to the dynamic IPLR test.
Figure 4 shows the results from a sample tread wear IPLR test for the same tire design used for collecting data shown in figure 2.
The tread wear IPLR test conditions were too severe, and hence, the tires wore out at a much lower mileage than the mileage of the dynamic IPLR test.
Note that 150 kPa is the approximate inflation pressure at the end of the 58,000 km long dynamic IPLR test previously described.
The tire that completed the dynamic IPLR test was buffed to one third of the tread depth, and run on the textured drum to get the tread evenly buffed to half of its original depth.
The dynamic IPLR test results were helpful in determining the worst possible inflation pressure loss conditions under simulated driving conditions, which is a pressure loss from 210 kPa to 150 kPa (30.5 psi to 22 psi) in 57,936 km (36,000 miles).
The static inflation pressure loss rate (IPLR) test (ASTM FI 112) widely used at present to compare tires' air retention capabilities is not applicable for dynamic operating conditions.