Which component must be adjusted during the setup of a tower crane to ensure stability?

The stability of a tower crane is significantly influenced by the positioning and weight of the counterweights. During the setup of a tower crane, the counterweights must be adjusted to balance the loads that the crane will lift and to help counteract the forces acting on the crane. This is because a crane's tipping moment is affected by the loads on the jib and the supporting base; thus, appropriate counterweights ensure that the crane maintains a stable center of gravity.

Having the right amount of counterweight also allows for safe operation under varying conditions, such as when the crane is slewing or lifting loads at different radii. Without properly adjusted counterweights, the crane could become unstable, leading to potential tipping or accidents.

Other components like jib length, load moment indicators, and operator controls play vital roles in the operation and efficiency of the crane but do not directly contribute to the stabilization of the crane during setup. Jib length influences reach and load capacity, load moment indicators are critical for safety and monitoring, and operator controls facilitate the operation but do not affect the structural stability when setting up the crane.