![]() The model assumes the driver uses “position control” of the car.There are no aerodynamic effects present.The car is in a constant forward speed (steady-state).This requires that the car goes through a corner under low lateral accelerations (lateral acceleration is high enough to generate slip angles, but low enough to keep the tyres from reaching the transitional range of operation The tyres operate in the linear (elastic) range.No pitch or roll motions, as defined on figure 1.Also, there is no longitudinal load transfer. ![]() This also presumes that there is no lateral load transfer on the car The steer angles of left and right wheels are assumed to be equal, and the front and rear axles are treated as single tyres (hence the name of the model) that generate a lateral force equal to the sum of left and right tyres on each axle.(.uk)įor this model, we will make the following assumptions: Yaw, pitch and roll motions defined along the principal axes of movement. Before reading this, I suggest you read my previous post “ The Absolute Guide to Racing Tyres – Part 1: Lateral Force”.įIGURE 1. Here one starts with a simpler model based on simplifying assumptions and escalates through it until it gets as close as possible to the complete reality of the functioning race car. This approach is called by the gods of Vehicle Dynamics, William and Douglas Milliken, in their legendary book Race Car Vehicle Dynamics (if you have not read a single chapter of this book, stop reading this post right now, and go buy yourself a copy, trust me, you will not regret this!) as the “Ladder of Abstraction”. Therefore, let us address the subject in a simpler way first, so that the fundamental concepts will be more easily understood. I will address full nonlinear car behaviour in a later post, but first things should come first. We will assume sublimit conditions, and the engineering definitions shown here should not be confused with the definitions of understeer and oversteer for behaviour at the limit of tyre grip. In this post I will explain neutral steer, understeer and oversteer in terms of steady-state cornering mechanics, in a linear way, i.e. Have you ever heard of neutral steer, understeer and oversteer? You probably have heard these terms, and you might even know what they mean, but do you know how it happens or what a racing car’s suspension has to do with it? If your answer to the latter question was “well, no…” or something similar, then this post might be useful.įirst, let’s make things straight.
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