A rough terrain crane set up on outriggers based on 85% tipping should have the tires positioned:

For a rough terrain crane that has set up on outriggers based on 85% tipping, the correct positioning of the tires is off the supporting surface. When the crane is operated with the tires off the ground, this indicates that the outrigger system is fully engaged to stabilize the crane and redistribute the load, which minimizes the risk of tipping during operation.

The design of rough terrain cranes allows for greater stability when they are set up properly on their outriggers, which extend out to provide a wide base of support. Having the tires off the ground ensures that the crane's weight is entirely supported by the outriggers, allowing for safer lifting operations at higher capacities. This setup is essential for maintaining optimal center of gravity and ensuring the stability required when lifting heavy loads.

In contrast, if the tires were on the supporting surface, there would be a risk of the crane tipping over, especially when lifting loads that may shift the center of gravity. The other options would similarly compromise the crane's stability and operational safety, reinforcing that the tires should indeed be off the supporting surface when set up for safe lifting operations.