Which of the following installation procedures can shorten the life of a timing belt?

Forcing the belt onto the pulleys can indeed shorten the life of a timing belt. This occurs because applying excessive force can cause unnecessary tension and strain on the belt. When a belt is forced, it may become distorted or damaged, leading to uneven wear or stress concentrations that compromise its integrity. This improper installation can result in the belt failing to maintain proper alignment, eventually leading to slipping, increased wear, or complete breakage.

In contrast, other procedures listed—such as installing at room temperature, lubricating the belt regularly, or using multiple pulleys—do not inherently risk damaging the timing belt under normal circumstances. Installing at room temperature ensures that the materials are not subjected to thermal stresses that could affect their properties. Regular lubrication (if specified by the manufacturer) can enhance operation and reduce friction-related wear. Using multiple pulleys may also be standard in certain setups and does not necessarily negatively impact the timing belt's lifespan, provided it is done properly.