A turning angle specification is not provided for all vehicles, but when available is specified in degrees for each wheel. The angle is measured by turning one wheel a specified number of degrees (typically 20), then measuring the angle of the opposite wheel. The difference should generally be about two degrees, and the same when the wheels are steered in the opposite direction.
If the turning angle is not within specifications or differs from side-to-side, it usually indicates bent steering arms. Other causes can include nonparallel steering linkage, a rack that is not level or a toe adjustment that was made without centering the steering wheel.
One way to check for bent steering arms is to measure the distance between the end of each arm and its wheel. The dimensions should be the same on both sides. If not, one or both arms may be bent. To determine which knuckle needs to be replaced, it may be necessary to compare the old and new knuckles since reference specifications for this dimension are usually unavailable.