This paper proposes a novel approach to shock-absorbing mechanism at impact in limit cycle walking focusing on the system redundancy. We consider a combined rimless wheel with a wobbling mass in the body frame. We mathematically show that the loss of energy caused by collision is reduced because the wobbling mass conserves the kinetic energy. Through numerical simulations, we show that the gait efficiency is determined mainly by the collision property. Furthermore, we develop a walking model taking the frame deflection into account using the previous model and discuss the dominant effect of micro vibration on the gait properties.