Two beam elements chassis/suspension models with rigid vehicle body representation and finite element tires were studied under proving ground conditions. The only difference between the two models was that one used flexible beam elements and the other used rigid beams. Several proving ground road surfaces were modeled and used in the analysis, including a washboard road surface, a Belgian block type track and a pothole track,. Also analyzed were the low speed driveway-ramp and (relatively) high speed lane-change cases. The proving ground simulation results, and system compliance results as well, were compared between the two models. The differences revealed the importance and necessity of using finite element model (even just using deformable beam elements) to include the component flexibility in conducting vehicle chassis/suspension dynamic analysis.