Full definition
Progressive deterioration of V-belt pulley grooves caused by friction from millions of belt engagement cycles, abrasive contamination, and corrosion. Diagnostic indicators: shiny or polished groove sidewalls (glazing), measurably widened groove angle (check with a groove gauge — Optibelt, Gates, or Continental gauges available), belt riding lower in the groove than on a new pulley, and black rubber residue on groove walls. A worn groove that is only 0.5 mm wider than specification can reduce power capacity by 10-15% and cause the belt to bottom out rather than wedge properly. Pulleys should be inspected at every belt change and replaced when grooves are out of tolerance per ISO 4183. Always replace pulleys and belts together for optimal contact. Cast iron pulleys typically last 2-3 belt changes before requiring replacement. Never machine grooves deeper to compensate for wear — it changes the pitch diameter and alters the drive ratio.