The front suspension unit for motorcycles is one of the functional parts for which continuous engineering improvement is required for advanced drivability. Especially, the ones for off-road motocross racing are frequently required to have their energy absorbing properties, ability to maintain tire-to-ground contact, driving comfort, etc. to be improved to meet the challenges of the racing courses which include many jumps, to exceed the performance of competitors, and to match the ever-improving performance of the engines and frames.To cope with the situation, the operability, rigidity and hydraulic pressure producing mechanism needs to be upgraded. As part of an improvement program, we have developed a air-oil separated front suspension which we have called the ‘twin chamber’ suspension.In this study, we compared the hydraulic pressure producing efficiency of the air-oil separated suspension with that of the conventional single chamber construction.The result of the comparison showed that the twin chamber suspension is less affected by the pressure hysteresis by 8% or more at the piston area and 50% or more at the partition area than the conventional suspension. In addition, for the twin chamber suspension, the rise of pressure becomes smoother to give a quicker response as the velocity increases.