The present study extends our recent result on the states estimation of two-wheeled vehicles. Based on the estimation of the lateral dynamics with the observer proposed in [1], a second estimator is presented in this paper to reconstruct the longitudinal tire-road forces, engine and braking torques. To this end, the longitudinal dynamics is analysed in order to recover the tire-road forces without any knowledge of tire parameters. The effectiveness of the proposed approach is shown through simulation results. Concluding remarks wrap up the paper.