If the rear wheels are not steered, the verticals on the two front wheels must intersect with the extension of the rear axle centre line at M (Figs 3.89 and 1.69) whereby different steer angles Si and Sa,o occur on the front wheels on the inside and outside of the bend. When the vehicle is moving very slowly and 'free of lateral forces', it will only corner precisely when the verticals drawn in the middle of all four wheels meet at one point - the centre of the bend M.
References 1 and 9 deal with this area in detail.
