How do I know when to replace sheave?

Belt-drive efficiency depends on full contact between the belt and the sheave walls. As a sheave wears, the walls where the belt should ride go from being flat to being “dished” or concave. Therefore, worn sheaves dramatically reduce the efficiency of the drive. Some symptoms of worn sheaves are…

  • NOISY DRIVE. As the walls of the sheave wear, the belt does more slipping than gripping, and tends to squeal. Belt dressing may reduce the noise for a while, but it does not restore lost metal to the sheave wall. A squealing drive may just need to be properly tensioned, but if the noise persists or returns shortly, check your sheaves.
  • ABNORMAL BELT WEAR. When tension forces a V belt to conform to a worn sheave wall, it runs hotter and its life will be shorter. A misaligned drive will wear more quickly on one side than the other, and can even cause the belt to flip over. If you keep burning through sets of new belts, you should inspect your sheaves.
  • VISUAL CUES. The worst sheave wear will be a highly-polished track in the sheave wall, deep enough that you can feel it with your finger. Lesser (but no less important) wear may be harder to spot with just your eyes. A sheave gauge, usually consisting of plastic wedges shaped like a new belt, can be inserted into the groove. If the gauge doesn’t fit squarely into the groove and you can see daylight around the edges, your sheave is worn and must be replaced.