OPERATION 12.21 HANDLING THE TIRES 12.21.1 PRECAUTIONS WHEN HANDLING THE TIRES If the following defects are found in a tire, for safety reason the tire should be replaced with a new one. ! Bead wire is broken or bent, or the tire is greatly deformed. ! Wear is excessive and the carcass ply (excluding breaker) is exposed for more than 1/4 of the circumference. ! Damage to the carcass exceeds 1/3 of the tire width. ! Tire layers are separated. ! Radial cracks reach the carcass. ! Deformation or damage which makes the tire unsuitable for use. 12.21.2 TIRE PRESSURE Measure the tire pressure before starting operations, when the tires are cold.
If the tire inflation pressure is too low, the tire will be overloaded; if it is too high, it will cause tire cuts and shock burst. To prevent these problems, adjust the tire inflation pressure according to the table on the next page. Deflection ratio = H - h x 100 H As a guideline that can be check visibly, the deflection ratio of the front tire (deflection/free height) is as follows. ! When carrying normal load (lift arm horizontal): Approximately 15 - 25 % ! When digging (rear wheels off ground):
Approximately 25 - 35 % When checking the tire inflation pressure, check also for small scratches or peeling of the tire, for nails or pieces of metal which may cause punctures, and for any abnormal wear. Clearing fallen stones and rocks from the operating area and maintaining the surface will extend the life of the tires. ! For operations on normal road surfaces, rock digging operations:................High end of range in air pressure chart ! Stockpile operations on soft ground:...............Average pressure in air pressure chart ! Operations on sand (operation not using much digging force)................. Low end of range in air pressure chart 2-57