Introduction to Mobile Cranes Practice Test

The main idea is how much safety margin a wheeled truck crane on tires must keep to stay stable during a lift. The margin of stability is the safety buffer between the load you’re lifting and the point where the crane would tip, expressed as a percentage of the tipping limit. For a wheeled crane that relies on its tires for support (often without outriggers), about 75% is used as the standard stability margin. This provides enough room to absorb real-world uncertainties like ground conditions, wind, and dynamic forces as the boom moves, without compromising tipping risk. The other numbers would either be too conservative or too optimistic for a mobile crane on tires, not leaving enough or leaving too little buffer for safe stability.