The U.S. NHTSA has established the FMVSS 126 standard that requires all vehicles sold in the U.S. to include an ESC system as standard equipment after September 1 st , 2011. There is growing concern among aftermarket suppliers specialized in development and installation of vehicle performance parts that chassis modifications may cause the ESC systems to be inoperative or can create unforeseen issues with stability and safety systems. This industry is in need of a process to support the development and validation of chassis modification. The authors propose the implementation of SIL and HIL simulations as a solution to the problem statement. Based on the results of a sensitivity analysis, guidelines for safe aftermarket modifications will be presented.