Track tensioning assembly is used in tracked vehicles to maintain the tautness of the track. The track tensioning system consists of the rear idler wheel which applies pressure on the track and a mechanism to increase or decrease the tension.This paper is a study of reaction forces and its effects on the chassis due to rear idler position. Rubber track layouts have been focus for most of the research work, here we study the effect of rear idler position on chassis structure through simulated analysis.An agriculture paddy combine harvester with rubber track is considered for the purpose of this work. Firstly the complete chassis structure is modeled in 3D using Creo and exported to Pro Mechanica for simulation. The real time forces, constraints were applied and the results were correlated to actual field results. The simulations were optimized through several iterations to match the field test results. For further optimization the chassis structure model has been simplified to carry out relative analysis for different tensioning positions.Relative position of the idler along the vertical axis was varied to study the effect of reaction forces on structure. Finally the results were compared to obtain the optimized position of rear idler through relative simulation. The optimized rear idler position is found based on reduced loads to the structure.