Issue link: https://read.dmtmag.com/i/34500
Afterward, the results are double-checked using shorter distances that are more easily obtained. In addition to these, the test tire is compared to a known baseline tire on a road wheel. This latter method is very accurate and very repeatable when using a similar baseline tire with a known tire revolutions per mile (Tire Revs./Mile). The Society of Automotive Engineers (SAE) procedure recognizes that within the test method itself, there will be some variation. In fact there are other factors that cause variation on the tire revolutions per mile's among similar tires. Be aware that they will have the same revolution per mile. The SAE procedure determines the tire revolutions per mile to within ± 1.5%. Some factors, which cause variation among tires, are: Load and Pressure – A difference in load/pressure could alter the tire revolutions per mile measurement by as much as 1.5%. If pressure is constant, going from an empty vehicle to a fully loaded vehicle can change revolution per mile by 1 to 1.5%. Treadwear – The tire revolutions per mile vary from a new tire to a fully worn tire. This can affect tire revolutions per mile by as much as 3% from the rated tire revolutions per mile. Tread Geometry – The height and stiffness of the blocks and the shape of the tread pattern can affect tire revolutions per mile. Torque – The presence of driving and braking torque can affect the tire revolutions per mile. Type and Condition of Pavement – Asphalt vs. concrete, wet vs. dry can create differences in tire revolutions per mile. CALCULATED TIRE REVOLUTIONS PER MILE Example: 445/50R22.5 MICHELIN (new tire) O.D. = 40.4 SLR = 18.7 d = (40.4/2) - 18.7 d = (20.2 - 18.7) = 1.5 Tire Revs./Mile = 20,168/(40.4 - (.8 x 1.5)) = 20,168/(40.4 - 1.2) = 20,168/39.2 Tire Revs./Mile = 514.489 (Calculated) vs. Data Book (Measured) tire revolutions per mile of 515. All the information required to determine the proper tire size is contained in the application specific data books. To select the proper tire size for a vehicle, it is necessary to know the maximum axle loads that the tires will carry and the maximum continuous speed at which they will operate. The maximum load that a tire can carry is different if it is mounted in single configuration rather than in dual. The allowable axle loads and the required inflation pressures to carry these loads are shown in the charts for both single and dual mountings in the current MICHELIN Truck Tire Data Book (MWL40731). The maximum allowable continuous speed is also indicated. ® X One XDN 2 ® ® 72 Appendix