What is Ackermann?
Ackermann is the angle of the inside tire in relation to the outside tire when the wheels are turned completely to either the left or the right.
In a tight turn, where the wheels are turned to full ‘lock’ (either to the left or right), the inside wheel is turning at a sharper angle than the outside wheel, allowing the inside wheel to follow a smaller radius than the outside wheel. This is called the ‘Ackermann Effect’.
If both the wheels were turned by the same amount, the inside wheel would scrub (effectively sliding sideways) and lessen the effectiveness of the steering. This tire scrubbing, which also creates unwanted heat and wear in the tire, can be eliminated by turning the inside wheel at a greater angle than the outside one.
Tuning with Ackermann
The standard setting (kit setting) on most vehicles is so as to make the vehicle easy to drive. Making the Ackermann Link longer (in most cases, the link will be swept back instead of parallel with the front suspension arms) will take away Ackermann, but make the steering more aggressive entering a corner. Making the link shorter (in most cases, the link will be more parallel with the front suspension arm) will result in more Ackermann, or less aggressive, and make the steering smoother and more predictable.
On cars with steering bellcranks, you can add a .100″ shim (2.5mm) under the ball end. You will also need to use a longer ball end to accomodate the spacer. This will result in more Ackermann.
Back to the RC Suspension Tuning Guide.