Okay, enough people have asked about measuring toe that I guess
I should post something. Warning: it's long.
There are many books which discuss easy home methods for checking
alignment. If you're at all interested in this sort of thing, you
should really get a copy of Fred Puhn's "How to Make Your Car Handle"
-- it's a great book and covers a lot of useful techniques as well
as theory of suspension design.
But here's a really easy, fast, two-person way to check toe. I use
this on my X1/9, which hasn't seen a professional alignment rack since
I bought it, and since I race it very actively, I consider proper
alignment *very* important, but I don't want to spend $80 every time
I make some kind of minor change to the suspension just to save myself
about five minutes of work (30 seconds to check, a couple minutes to
change it if it's wrong, another 30 seconds to recheck).
1. Drive the car to a level parking place.
Ideally you want the car loaded as it will be when it is driven
(e.g. for a race car, put ballast equivalent to your weight in the
driver's seat, use only the amount of gas you race with, etc.)
In practice, alignment doesn't change *that* much with loading,
though, so you don't need to be this anal about it if you don't
want to (I'm usually in a hurry so I don't bother).
However, it's important that you drive the car straight forward
to the place where it will be aligned -- once you turn the wheel,
or jack the car up and then set it down again, you've changed the
static alignment and the numbers you measure will be wrong.
2. (This part I got from Brad Martinson, and it's a really neat hack.)
Get two straight pins and stick one into each front (or rear, if
you're checking rear alignment) tire on the front of the tire at
some constant height H above the ground. H should be lower than
the ground clearance of your car in the neighborhood of the wheels.
3. Have a friend hold one end of a tape measure against the tire starting
at one pin. You stand on the other side of the car, pull the tape
measure so that there's no slack and measure to the other pin.
4. Roll the car back (not forward, you'll roll over the pins!) until the
pins now stick out the back end of the tires and are again at height H.
5. With friend, again measure between the pins.
6. The difference between these measurements is your toe.
Notes: you don't need pins (in fact, I seldom use them) as long as you
can pick a repeatable place on the tread from which to measure (easy
with A008's, difficult with Comp HR's, depends on tread pattern).
An easy way to make sure H is constant is to use a piece of 2x4 as
a marker (4" seems to be a good height on a lowered X1/9; on most
cars you could probably measure somewhat higher). Measure as high
as you can, because you get better accuracy that way (the tire sticks
out more higher up, so you're measuring bigger numbers and your error
is a smaller percentage).
In practice, 1/32" is plenty of accuracy for measuring toe (you don't
really know precisely what your front toe should measure to better
than 1/32", do you? I sure don't, and I've been experimenting with
my car's handling for three years. Optimal settings change according
to tire compound, my mood, wear in the suspension bushings, how cold
and wet the weather is, etc.).
If you want a bit more accuracy, then put the car on alignment plates.
Get four thin squares (about 6"x6"x3/16", say) of some smooth metal,
like Aluminum. Use them to make two sandwiches of metal outside,
oil or grease inside. Now put one sandwich under each tire. Now
you have an alignment plate just like the professionals use (only
a lot cheaper) and you can turn the wheel, move the car, etc. without
screwing up your static toe measurement. You can't use pins or roll
the car back any more, though.
One-person toe measurement:
This is considerably more hassle, but there are several ways to do
it. You can set up two strings parallel to each other and to each
car's centerline, and measure from the strings to the front and back
edges of your wheels. (Setting up the strings takes from 20 minutes
to over an hour; once they're set up, checking the toe takes about
one minute to do all four wheels, unless you trip over the strings,
in which case you have to set them up all over again.) I hate
this method.
A method I like better is to drop a vertical (using a plumb-bob) from
the centerline of the front and rear of each tire (do the rear, too,
while you're at it. Yeah, even if it's non-adjustable -- might
as well check it, because this will tell you whether your frame
is straight, so it's a good thing to do on a new car). Make a
mark on the floor of the garage below each tire centerline. Now
drive the car away and draw lines all over the place and measure
all of them: you can get front track, rear track, right and left
wheelbase, front and rear toe, and diagonals between the tire
centerpoints. Comparing things like the diagonals and the right/
left track will tell you how straight your frame is.
Cheap and easy camber measurement:
I've tried a few camber gauges (Larry, remind me sometime to give your
camber gauge back!) but I find them more difficult to use than this
method. (I think there are easy-to-use gauges, I just haven't seen one).
If you're measuring camber with the intention of changing it if it's
wrong, do it BEFORE you measure toe -- on most cars, changing camber
will also change toe.
Get a carpenter's level. You want one which is slightly shorter
than your wheel size (e.g. on my 13" rims a 12" level works okay).
Rest the bottom of the level against some repeatable part of the
wheel (like the bottom of the outside edge of the rim, but you'll
need different techniques with some wheels). Now swing the level
(without losing contact with the wheel) until it's exactly vertical.
Using a caliper (you can use a ruler, but a caliper is much easier)
measure the distance from the level to the wheel. Now you have your
camber in inches. Some trigonometry can give you the camber in
degrees, if that's what you want.
There are lots of variations on this -- you can use a coarse-thread
screw instead of a caliper, and count turns. You can use a dial
indicator instead of a caliper. You can make a gizmo with sliding
fingers that stick out from the level and contact the wheel at just
the right points for your size wheel. You can just hold the level
against the wheel and make calibration marks on the window where
the bubble appears. You can use a vertical from the floor and
measure from there to the bottom and top of the wheels, then subtract.
Whatever seems easiest for you.
--
...Akkana (akkana@apple.com)
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