# Cutting the Corner: Cornering Compliances, Bundorf Analysis and Understeer Budget

## A budget of different sources of understeer

Direction Control of the vehicle can be quantified by many metrics but no other metrics is more talked about than understeer gradient. It has given a quantitative meaning to vehicle understeer and oversteer. The SAE definition for understeer is as follows: “*A vehicle is understeer at a given trim if the change in reference steer angle per unit change in steady-state lateral acceleration at constant speed is greater than the change in Ackerman steer angle per unit change in steady-state lateral acceleration.*”

If we talk in mathematical terms, a simple expression for understeer can be derived from a basic bicycle model. As mentioned in my previous story, the general equation for bicycle model can be written as:

The different variables here are explained in my previous story

If we write the above equation as :