This article presents the dimensionless model and the design considerations of a pneumatic suspension with auxiliary reservoir. The dimensionless model provided makes it possible to fully understand the effect of the parameters which define the suspension and to select the spring type correctly. Without this selection, the suspension generates transmissibility curves with excessive amplification in the vicinity of the resonance, even after optimum definition of auxiliary volume and resistance. This aspect is the key point for defining effective applicable solutions. The design considerations provided at the end of the work constitute a useful résumé and a guide for designing suspensions of the type described.