An isolator for isolating a device driven by an engine via an endless drive member is described. The isolator comprises a shaft adapter that is connectable with a shaft of the device, defining a shaft adapter axis, a rotary drive member that is rotatable relative to the shaft adapter and has an endless drive member engagement surface that is engageable with the endless drive member, and an isolation spring arrangement positioned to transfer torque between the shaft adapter and the rotary drive member. The isolation spring arrangement has at least one isolation spring that is axially offset from the endless drive member engagement surface. The at least one isolation spring has an outer edge that is radially outside the endless drive member engagement surface.