Issue link: http://read.dmtmag.com/i/34501
RECOMMENDATIONS FOR THE USE OF DYNAMOMETERS SEVERE DAMAGE can result in the crown area of radial truck tires when run on dynamometers for extended periods. Quite often the damage is internal and not discovered until after the vehicle has been put back in service. In order to avoid the possibility of damaging MICHELIN ® radial truck tires, adhere to the following time/speed restrictions and related test parameters. This applies to tire sizes with bead seat diameters of 19.5, 20, 22, 22.5, 24, and 24.5 inches. NOTE: The times for the indicated speed in the chart are not additive. MAXIMUM TIME (MINUTES) Speed (mph)* 62 (Max.) 50 40 30 20 10 On 8 5⁄8" Dia. Rollers 2.5 3.5 5 7.5 16 42 On 18-20" Dia. Rollers 4 6 8.5 14 35 105 *Exceeding the legal speed limit is neither recommended nor endorsed. Note that in the above speed/time table a significant increase in time is allowed on the 18-20" versus the 8 5⁄8" diameter roller. For example, at 30 mph time almost doubles from 7.5 minutes to 14 minutes. • Allow a two-hour cool-down between tests. • These limits are for an empty vehicle with tire pressures as indicated on the tire sidewall for maximum load. • Allow a one-hour cool-down after each test before loading vehicle. The maximum allowable center-to-center distance between the two rollers in contact with a tire is a function of the sum of tire and roller diameter. MAX. ROLLER SPACING Tire Size 275/80R22.5 XZE Tire O.D. 8 5⁄8" Dia. 18" Dia. 40.2" 28" This relationship is shown below: Maximum Roller Spacing 33.5" = Tire Diameter + Roller Diameter x 1.15 2 For example using 8 5⁄8" diameter: 40.2" + 8.625 x 1.15 2 = 48.825 x 1.15 2 = 24.4125" x 1.15 = 28.07" 44 Section Three: Extending Tire Life If these times and/or speeds are exceeded, irreversible internal damage in the tire could result, leading ultimately to tire destruction. When it is anticipated that a test will exceed these time/speed values, use “surrogate” tires (a tire used in place of the normal tire).