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File description: Front Wheel Alignment Your name: (optional) Randall Young
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There are several methods, including a good 4-wheel method written up in
GrassRoots Motorsports last year. If you want, ask me to dig up the
issue reference.
To check toe-in, I use a 'tool' made up of a 8' length of 1x2, with two
5" x 11" rectangles of Masonite fastened to it roughly 5' apart, spaced
to match the track of my vehicles. The extra 3' of 1x2 just forms a
handle, to make it easier to grab.
To use it, I first jack up the front of the car, and spin the tires
while making a mark around the outside of the tire. It doesn't matter
where the mark is, and it doesn't have to be in the same place on each
tire.
Then I lower the car to the ground, bounce it and roll it back and forth
a few times to let the suspension 'settle'. You can also buy or build
sliding plates to make this step easier. I'm told two 12x12 pieces of
flat 1/4" steel with grease between them work pretty good, but I haven't
tried it.
Lay the 'tool' behind the tires with the 1x2 on the floor, and the
masonite pieces vertical with the short edges resting against the tires
at roughly the centerline. I start with the masonite flat on the floor,
and rotate them up into the wheel wells behind the tires. Transfer the
marks from each tire to the edge of the masonite.
Then put the 'tool' in front of the tires, again with the masonite
pieces resting against the center of the tire, and compare the marks.
With the mark on one side lined up exactly, you can measure the toe-in
in inches between the mark on the masonite and the mark on the tire, on
the other side. Or, divide the measurement by the overall tire diameter
(typically 22-28 inches, depending on tire and wheel size) and take the
arc-sin to get the toe-in in degrees.
To check camber, I use a temporary tool made of a carpenter's square,
with two 6" steel rules clamped to it with small C clamps. The short
arm of the square rests on the floor (which must be reasonably flat for
this to be accurate), and the steel rules are positioned to touch the
wheel rim not on the very edge, but just inside it on the flat part. To
calculate the correct measurement, take the sin of the specified camber
angle, and multiply by the wheel diameter (eg 14 inches).