Which of these could cause U-joint angles to change from their normal angles?

A lowered ride height can indeed cause U-joint angles to change from their normal positions. When the ride height of a vehicle is lowered, it affects the alignment and position of various components in the drivetrain. This adjustment can alter the operating angles of the U-joints, which are designed to maintain a specific angle to work effectively.

When the vehicle's body is closer to the ground, the angle at which the driveshaft meets the differential and transmission may become steeper or shallower than designed. This alteration can lead to increased vibration, noise, and ultimately wear or failure of the U-joints if not corrected. Adjusting the suspension to maintain proper angles after modifying the ride height is essential for maintaining the drivetrain's functionality.

Factors like increased wheel diameter, worn suspension components, or improperly installed tires can also affect vehicle dynamics, but they don't directly influence the U-joint angles in the same way that a change in ride height does.