TURNING ANGLE
Turning angle refers to the change in toe that occurs when the wheels are steered to either side. This is also called "toe-out on
turns." If toe didn't change and the wheels remained parallel when turned, both front tires would squeal and scuff because the
inner tire has to follow a smaller radius path than the outer tire. To compensate, the steering arms and linkage are usually
designed to provide a slight change in parallelism (toe) so the inner wheel can turn more sharply than the outer wheel. This is
the "Ackerman" principle of steering.
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.
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