Ackermann Steering - An Overview

For a true rolling of a four wheeled vehicle moving on a curved track, the straight lines drawn through all the wheel axes must intersect at the instantaneous centre.

The Ackermann steering uses the two front steered wheels pivoted at the finishing points of an axle-beam. There is an original Ackermann linkage which usually has parallel set track-rod-arms ensuring that both steered wheels swivel equally. Consequently, the projection lines do not meet at one point.
In case both of the front wheels are allowed follow their own natural paths, they would ultimately
converge and come across each other. As the vehicle will have to move along one mean path, so both of the wheel tracks would conflict which may cause tyre slip and tread scrub.

Therefore a modified linkage is used at inclined track-rod arms so that the inner wheel swivels about the king-pin a little bit more than the outer wheel.