What is the minimum stability for a crane on rubber?

• A. 65%
• B. 75%
• C. 85%
• D. 90%

Answer: (B)

Stability here means how well the crane can resist tipping when it’s operating on rubber tires. Without the solid support of outriggers, a mobile crane is more prone to overturning, so a safe margin is needed. The minimum stability percentage sets the smallest margin you must maintain between the resisting overturning moment and the actual overturning moment during lifts on rubber, giving you a buffer for ground conditions, wind, and dynamic forces.

Among typical safety standards for cranes on rubber, 75% is the established minimum. It provides a practical, safe limit that balances safety with operational capability. Lower values would leave too little margin and higher values would be unnecessarily restrictive for everyday work.