<p>Time delay feedback control has been widely studied in vehicle body vibration reduction, but the influence of different feedback states on stability and vibration reduction is not fully understood. In this paper, a simplified vehicle suspension model is used to investigate different time delay feedback control states on suspension stability and vibration reduction, to clarify which feedback state can effectively improve vehicle comfort and driving safety. Six different time delay feedback control systems are established by combining two feedback objects (vehicle body and wheel) with three feedback variables (displacement, velocity, and acceleration). The stable region independent of time delay (SRITD) and switching stability regions of time delay control systems with six different feedback states are investigated using the polynomial solution method and the Routh-Hurwitz criterion. Subsequently, the control parameters of the six model sets were optimized within their stable regions using a variable-weight particle swarm optimization (VWPSO) program. The vibration reduction performance and stability region laws are derived by comparing the frequency response characteristics and the root mean square (RMS) values of vehicle vibration. The results show that the two states based on wheel velocity and body acceleration have obvious vibration reduction effects, and have a wide vibration reduction frequency band. This study guides the selection of different feedback state variables for time delay control.</p>