Toe In/Out is a measurement of wheel angle when looking down at the vehicle. Toe out is when the front of the wheels are further apart than the rear wheels.
Because the wheels on the inside need to turn at a sharper angle than the outside, some toe-out on the front wheels help improve handling of the vehicle. Sometimes toe-in is added to the rear to improve stability.
Adjusting Toe In/Out
The toe setting is adjusted to keep the vehicle pointed straight and stable on public roads, which often have a slight angle to them so they allow rain water to drain off.
Adjusting Front Toe
On most vehicles, the front toe setting is the easiest alignment angle to adjust, and only requires the turning of the outer tie rod ends in relation to the inner.
Because toe adjustments alter the angle of the wheel around its steering axis, the caster setting will cause any toe adjustment to alter the camber angle as well.
Adjusting Rear Toe
Rear toe settings are usually much more difficult to adjust, unless there is rear wheel steering or non-steering tie rod ends on the vehicle. In models without such parts, other areas must be adjusted, depending on the type of suspension system used.
Some vehicles are equipped with toe links, which have a threaded rod which can be repositioned by turning the end of the toe link in relation to the portion
When a vehicle travels around a corner, the outer wheels travel a further distance than the inner wheels, and the outer wheels also don't have to be turned as sharply to get around that curve. Because of this, the steering system has design considerations (usually an offset steering knuckle hole for the outer tie rod ends) to progressively alter the toe angle when the wheels are turned.