Belt drive hardware has rotational speed limits in order to prevent excessive hoop stress levels that could result in physical material failures. Material failures can be catastrophic with fragments thrown outward at high velocities and energy levels, so speed limits should not be exceeded.
Speed limits are based on the hardware material, as well as on the hardware configuration. Block style hardware is inherently stronger than hardware with rims or spokes, so can operate at higher speeds.
Rotational speed limits are most commonly expressed in terms of rim speeds. Common units used to express rim speed are feet per minute (ft/min) and meters per second (m/s). Maximum rpm limits can be calculated from rim speeds with hardware diameters known. An equation to calculate hardware rpm from rim speed is as follows:
RPM = (Rim Speed (ft/min) x 3.82)/Diameter (in)
A table from the Mechanical Power Transmission Association Standard B13i-2013 containing rim speed limits for a variety of hardware configurations and materials is as follows:
Belt drive hardware is often stamped with maximum rpm values, and will likely be based on this data.