FSAE Steering Geometry

Problem

Due to the nonlinear characteristics of tires optimizing the angle of the tires when turning is important for the handling of the car. Tire characteristics such as slip angles, and alignment moment can heavily impact the feel and overall performance of a race cars. Values like ackerman, caster, kingpin inclination all allow us to optimize the tire characteristics. 

Solution

The process for optimizing steering geometry begins with analyzing tire data from a non profit testing organization called the Tire Test Consortium. The issue with the TTC data is it is gathered from testing on a sandpaper track which means all tire data has to be scaled. From three I drew out diagrams of how much vertical force and how much lateral force was required from each tire to determine the slip angle at each tire.  From there I aligned the slip angle of each tire to our skid-pad radius to optimize lateral grip for the skid-pad radius. From there I back calculated the ideal steering angle for each tire and determined the required ackerman angles. 

Things I did wrong

1. I assumed that there was a constant scaling coefficient for TTC data, when in reality the coefficient gets smaller at higher slip angles.

2. I thought that the lateral force from a tire was perpendicular to the slip angle as opposed to perpendicular to the heading of the tire. 

3. used poorly fit tire data

Results

My analysis contributed to a 19/25 score in our vehicle dynamics design presentation at the 2026 FSAE EV michigan competition, a new high score for for the team.