In an automotive twin tube shock absorber, thin structures used in piston and base valve sub-assembly are called shims. These shims are used in proper combination to achieve particular damping force characteristics and these shims will be operating continuously throughout the life of shock absorber. Any failure of shims during lab/ vehicle testing will increase the development time and cost considerably. Hence, predicting the operating life of shim assembly is very important during shock absorber development stage.In order to predict the life of the shim assembly, simulation techniques can be applied with fair degree of accuracy. Currently, during structural simulation of shim assembly, it is assumed that fluid pressure is acting uniformly over the entire shim to find stress intensity. This approximation is taken into account to predict the fatigue life of shim assembly.This paper proposes additional technique to carry out close to real life shim simulation. In this proposed technique, fluid structure interaction (FSI) is considered for modelling the shock absorber fluid flow and piston shim assembly. In this simulation, actual pressure developed during shock absorber travel will be acting on shim assembly. The fatigue life is calculated for current and proposed techniques. These results are compared with experimental results for deciding appropriate simulation technique.