As drivers steer a road vehicle along the desired trajectory, they will experience resistance from the steering wheel that they must overcome to maintain a constant steer angle.
That resistance is known as the aligning moment and acts to return the steering alignment to the centre. Understanding and controlling the aligning moment in a race car is essential to maintain balance and drivability.
This Tech Explained article will cover the different sources of the aligning moment, its effect on vehicle balance and performance, and how it shapes the subjective driving experience, with some general design considerations for the race car engineer.
How aligning moment is generated.
The aligning moment has four primary sources. Three relate to tyre forces, which you can review in this previous Tech Explained article. The first source is a direct function of the tyre construction. Figure 1 below depicts the tyre deformation present when rolling at a slip angle. Figure 1
 
The tyre’s structure resists this twisting deformation, generating an Aligning Moment acting to restore the tyre to a free-rolling orientation. The second source is a function of the tyre contact patch in cornering known as the pneumatic trail. See figure 2.
Figure 2
When a tyre is generating lateral force under a slip angle, that force unequally distributes along with the contact patch. Instead, lateral force gradually increases rearward until the tyre can no longer sustain the slip angle, at w...