In this work, the aerodynamic analysis of the original and modified Ahmed body was done. The principle of modification was the chamfer angle on the back sides of the Ahmed body like a boat tail, which was expected to decrease the magnitude of the drag force. The value of the aerodynamic coefficients was carried out using CFD modelling and data were validated in wind tunnel measurements. For those measurements, it was necessary to design simple aerodynamic balances, since the utilized wind tunnel was not equipped with any. It has been expected that the drag force coefficient of the modified model should be reduced compared to original geometry.