Issue link: http://read.dmtmag.com/i/41477
Appendix PROPER APPLICATION OF ON/OFF ROAD (Y AND L) TIRES* The tires with "Y" or "L" (see Page 25) as the third character in the tread designations are designed and optimized for on/off road applications and are speed restricted. These tires should not be used in applications that operate the tires continuously on highway over an extended period of time or at speeds that exceed the speed rating of the tire. This could lead to heat build up and cause premature or sudden tire failure. Tires with the "Y" designation are for applications expected to be 80% On-road use and 20% Off-road use. They have a maximum speed of 65 mph. Tires with the "L" designation are for applications expected to be 20% On-road use and 80% Off-road use. Some of the "L" designated tires have a maximum speed of 50 mph while others have maximum speeds of 55, 60 and of 70 mph. The Tire and Rim Association (TRA) permits operating a 65 mph rated tire at higher speeds with a reduced load and increased inflation. No such permission is granted by TRA for tires with speed rating rated below 65 mph. Always refer to this MICHELIN Truck Tire Data Book on Page 25 and match the tire to the application when making tire selections. COLD CLIMATE PRESSURE CORRECTION DATA Because the pressure inside a tire will decrease when the vehicle is taken from a warm environment to a cold one, some adjustments may be necessary when adjusting the tire pressures of a vehicle to be operated in very cold temperatures. These adjustments are only necessary if the pressures are verified and adjusted inside a heated garage with an air supply that is also at the higher room temperature. (No adjustment necessary if done outside.) In extreme cases, the following table should be used to ensure that the operating pressure and deflection of tires are adequate at the outside ambient temperature. Using the load and pressure charts below, determine the appropriate "Recommended Pressure" required for the axle load. Then find the same pressure down the left column of the table to the right. Going across to the relevant outside ambient temperature you will find the corrected inflation pressure to be used. For example: • A log truck in Alaska has a front axle loaded weight of 12,000 lbs. • The truck is equipped with 11R24.5 MICHELIN® XZY® 3 tires. • The recommended pressure for this fitment is 105. • The truck is parked overnight in a heated garage. • The outside high forecasted for today is -20ºF. • The tire pressures are checked and adjusted prior to leaving the heated garage. According the chart below, the tires should be adjusted to 128. Adjusted Inflation Pressure (psi) (when inflating indoors at 65°F [18°C]) Recommended Pressure (psi) 75 80 85 90 95 100 105 110 115 120 125 130 F° 50° C° 10° 78 83 88 93 98 103 109 114 119 124 129 134 40° 4° 80 85 90 95 101 106 111 116 122 127 132 137 30° -1° 81 87 92 98 103 108 114 119 124 130 135 140 20° -7° 83 89 94 100 105 111 116 122 127 133 138 144 Outside Ambient Temperature 10° 0° -12° 86 91 97 102 108 113 119 125 130 136 141 147 -18° 88 93 99 105 111 116 122 128 133 139 145 150 -10° -23° 90 96 102 108 113 119 125 131 137 143 148 154 -20° -29° 92 98 104 110 116 122 128 134 140 146 152 158 -30° -34° 95 101 107 113 119 125 132 138 144 150 156 162 -40° -40° 98 104 110 116 123 129 135 141 148 154 160 166 -50° -46° 100 107 113 119 126 132 139 145 151 158 164 171 91