What causes a V belt to obtain shiny sides immediately following installation?

When a V-belt shows shiny sides shortly after installation, it indicates that the belt is experiencing excessive friction against the sheaves (pulleys). This shiny appearance is a result of the belt rubbing against the sheaves when it’s not fitting properly or is misaligned.

A worn sheave can lead to improper engagement of the belt's grooves, preventing the belt from seating correctly. As the belt operates, it may slip or struggle to maintain contact in the grooves, generating heat and wear that create the shiny surface. This situation can occur if the pulley’s surface is grooved or damaged, leading to poor traction or alignment issues.

The other options suggest various potential mechanical issues, but they would not directly cause the shiny surface unless accompanied by misalignment or poor fitting. For instance, if the belt is the wrong size, it could lead to slipping; however, a worn sheave directly explains the shiny aspect on the belt itself. Thus, recognizing the role of the sheave's condition in the belt's performance is critical in maintaining proper power transmission without irregular wear signs.