Full definition
An inherent phenomenon in friction-driven belt systems where the belt elongates slightly on the tight (loaded) side and contracts on the slack (return) side as it transfers power, causing the driven pulley to rotate marginally slower than the theoretical ratio predicts. Creep is not a defect — it is the mechanism by which friction belts transmit power. Typical creep: 0.5-1% of belt speed. Distinct from slip, which is an abnormal condition caused by insufficient tension or overload. The speed loss due to creep is predictable: driven RPM = driver RPM x (D1/D2) x (1 - creep%). Per ISO 5292. Creep cannot be eliminated in friction drives; it can only be minimized through proper tensioning.