Because of steering geometry in a turn, the front wheels of cars used on
> pavement are not parallel but are slightly toed-in. This is best
determined
> with an instrument that reads the toe-in in degrees since the differing
size
> of tires and wheels means different dimensional distances for the same
number
> of degrees of toe-in. However, for a given vehicle, once the wheels are
> properly aligned and the toe-in established, you can determine the
> dimensional difference and thereafter use that to quickly check or adjust
> your toe-in. On older vehicles having king-pin style steering spindles,
> where camber is set by stacks of shims, adjusting the shim stack always
> causes a slight change in toe-in which should then be reset. I do not know
> of any ball-joint type suspensions that permit such adjustments; replacing
a
> worn part, such as a tie-rod end should restore proper alignment
> automatically.
>
> The measurement for toe-in is made first at the rear of the wheel at a
point
> on the tire or rim horizontal with the axle. The measurement is made using
> two sticks, each pressed against the measuring point of opposite wheels.
The
> sticks are allowed to overlap and the free ends held horizontal by the
> mechanic. The point where the sticks overlap is scribed onto one of the
> sticks. The vehicle is rolled backwards until the measuring point is
brought
> to the front and is the same height above the pavement as it was when the
> measurement was taken at the rear. The front track width is measured and a
> second point is scribed on the stick.
>
> The distance between the scribe marks reflects the toe-in.
>
> On my 1965 VW bus, fitted with 15" rims, proper toe-in is reflected by a
> measurement of .10" to .12" -- between an eighth and a tenth of an inch. I
> usually shoot for the smaller figure. Other vehicles will have a different
> dimension due to the differences in the point at which the measurement is
> taken, different rim diameter, etc.
>
> There are commercially made measuring rods that are spring-loaded, allowing
> you to fix them between the wheels then simply roll the vehicle back and
> forth. If such a device will work on your vehicle -- it hits the steering
> components on some designs -- you'll find it very handy since you can
adjust
> the toe-in with the measuring tool in place and actually see the gauge-mark
> move as you lengthen or shorten the tie-rod.
>
> If you think about it you will see that there are a number of ways to
measure
> toe-in. The use of two sticks -- or two pieces of welding rod, two
sections
> of plastic pipe, a pair of yard sticks and so forth -- is simply one of the
> handier ways methods. With nominal care, and in light of the generous
> tolerance in most toe-in specs, the results are more than accurate enough
for
> normal use.
>
> -Bob
>
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