Tire manufacturers and road managers use specific vehicles and systems to assess road grip between reference roads or tires. This study details the development of a front-wheel braking method, enabling grip measurement with or without anti-lock braking systems (ABS). By modifying a vehicle to apply brakes only to the front wheels on a test track, this approach simplifies the grip calculation and increases safety by preventing rear wheel slip on low-texture roads and in wet conditions. Thus, this method provides the necessary safety conditions for evaluating braking with locked wheels on slippery surfaces, in addition to conventional tests with ABS. Both grip values, with and without ABS, can be used to construct a complete slip-grip curve, using a Pacejka model, from 0 to 100% slip. An instrumented passenger car was then used to measure grip on a test track and two highway sections at initial speeds of 50, 65, and 80 km/h. The method shows good repeatability across tests for given road conditions. A comparison between our "406" vehicle with the front braking method and a continuous grip measurement vehicle (CGM) showed about a 5% difference at key points of the curve, corresponding to locked and fully sliding wheel scenarios. Thus, our 406 vehicle's results may more accurately represent the grip of similar light vehicles than a dedicated vehicle using a small instrumented fifth wheel.

road grip; braking; instrumented vehicle