Weight is one of the important design drivers of automotive members. In case of primary load bearing members such as the chassis, the design process is driven by numerous manufacturing and performance conditions. As a result weight saving efforts can only be taken up in later design cycles rather than in the preliminary ones. A robust optimization approach would lead to weight savings without significant deterioration in performance. The size optimization runs are carried out on the actual chassis frame. The chassis was analysed from various perspective. The FE model is created using Hypermesh. The modal analysis and static analysis of the chassis are carried out using MSC/NASTRAN. The in house code GENSIZ was used to carry out the optimization runs. The optimization results brought up thousands of alternatives from which desired ones could be extracted. The mass relocation leads to a decrease in distortion by 16.4%, 17% and 5%.The cross assessment of modal thickness data analysed for distortion study shows reduction of 19% mass, 7% frequency and 1% in distortion. We conclude that GENSIZ could yield robust designs with significant weight savings even in advanced design cycles.