Confessions of an Automationeer, Part 197: Toeing the Line

Confessions of an Automationeer, Part 197: Toeing the Line

Toe angle (the angle at which the wheels are aligned relative to a car's longitudinal axis) was only made adjustable in more recent UE4 builds of Automation, but since then it has become an integral part of configuring a car's suspension. In-game, it is represented by the amount of toe-in angle - thus, a toe-in setting of 0 degrees represents neutral toe, and any negative amount of toe-in represents toe-out. Here's how it works, as demonstrated by a test mule I'll take a deeper dive into in the next post.

Above: An example of a neutral handling setup, with a 50/50 balance between oversteer and understeer. It's not just the amount of tire stagger, weight distribution, camber angle, spring rates, and anti-roll bar stiffness that determines a car's handling balance - so what else could cause this?

The car in question is mid-engined, rear-wheel-drive, hence the 20mm tire stagger between the front and rear wheels. But this on its own is insufficient to compensate for its 43/57 front/rear weight distribution. The best way to combat the resulting oversteer (even with the amount of tire stagger used) is to increase the toe-in angle - in this case, to 0.25 degrees per axle.

Above: The greater the rearward bias of a car's weight distribution, the more toe-in angle will be required to counteract oversteer; conversely, if a car's weight distribution skews heavily towards the front, it will need more negative toe-in angle (i.e., toe-out) to reduce understeer.

There are some problems to be aware of, though. Depending on a car's weight distribution, having insufficient toe-in angle will lead to a (potentially terminal) oversteer bias, and using too much toe-in angle will lead to an understeer bias - both of them are undesirable (especially if the resulting bias is terminal), since they will result in reduced sportiness and drivability.

Above, from top: Too little toe-in angle will lead to an oversteer bias; too much will cause an understeer bias. In the latter two pictures, the bias has become terminal due to excessive toe-in/toe-out angle.

Hopefully this clears things up regarding how toe-in/toe-out angle works, as well as when and how much of it should be used.