When might ropes or belts need to be shortened?

Shortening ropes or belts is often necessary to maintain proper counterweight runby. The counterweight runby refers to the distance that the counterweight needs to travel, which must be accurately adjusted to ensure smooth and safe operation of the elevator system. If the ropes are too long, it can lead to issues such as excessive movement or instability in the counterweight, potentially causing operational issues or safety hazards.

Proper adjustments help maintain a balanced system where the counterweight effectively matches the weight of the elevator car, thereby allowing for efficient operation. This aspect is crucial because if the runby is not maintained properly, it can adversely affect the elevator's functionality, leading to increased strain on the components and possible malfunctions.

The other choices focus on different aspects of elevator operation, such as speed, wear, and load capacity. However, they do not address the specific need to maintain counterweight runby, which is the primary reason ropes or belts would be shortened in this context.