Back yard Alignment
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Author: Jan Vandenbrande & Mark Sirota
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Date: Wed, 30 Aug 89 11:07:34 PDT
From: Jan Vandenbrande
Subject: Checking Alignment yourself
Well this is one way to do it at home. Note that the accuracy is not
great, it just lets you know whether you are in the right ball park.
Camber:
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1) Put the car on a level smooth surface (at least level sideways => If
not see later). Bounce the car up and down and let the shocks settle in.
(NB: Tires should be pointing straight ahead).
2) Use a plumb bob (you know the string with the bullet like weight on
the bottom) and suspend it such that it goes across your L/F fender,
passing through the center line of your front axle. (You can also use a
big precision metal square (L-shaped thing at 90degr) or a combination
of both).
3) Measure the distance from the string to the edge of your rim for both
the top and bottom parts. Don't mix the two numbers.
4) Do the same for the other tire.
5) Roll your car so that the tires rotate 180 degr, and repeat the
measurements. Take the average for each set of measurements. This takes
care of the error caused by bent rims.
6) If the floor is not perfectly level, turn the car 180 degrees (not
upside down :-|), and repeat the entire procedure for both sides, and
take the average of all numbers.
7) Now sit down and measure the distance between the two points you used
to take these measurements.
8) Sit down somewhere, dust off your old calculator, and calculate the
angle of the triangle formed by the string and the distance to the top
part of the rim (actually you have two equi-angular triangles). Dig up
your high school trig book.
The angle is considered negative if the top part is further away from
the string (i.e. top pointing inwards). The accuracy of your result is
somewhere around 1/2 degree, not great, but if you get angles of the
order of several degrees, you may have a problem.
See your manuals for the correct camber settings. Old VWs use an
eccentric bolt, newer ones require another skinnier bolt to perfrom
adjustments.
Toe
---
I haven't done it this way, but this should work (or at least let you
know whether you are in the right range).
1) Start with a level smooth floor, bounce, tires straight ahead, etc.
2) Take a large square (L thing again), and measure equidistantly (to
clear the tire) from the front and rear side of the rim with one side of
the square on the floor & make a mark for each on the floor. Do this for
both sides.
3) Now measure the distance between the L/R fronts & L/R rear dots on
the floor.
4) Roll the car so that the tires rotate 180 degrees, repeat & average
out the two measurement.
5) Do the trig thing again. Actually, what you are interested in is the
difference in angle between the toe of L & R with respect to the forward
direction. Note that some shops don't give the toe in degrees but rather
in inch or cm.
There are tools to do some of these things (like this bubble thing to
measure the camber) but they are probably too pricy for the casual user.
I can imagine that there are several more schemes of measuring things,
all probably requiring more sophisticated tools (which you could make
yorself).
Concerning the accuracy of those machines in the shop... Hmmmm,
sometimes I wonder as they are not too gentle with them. And do you
trust the high school drop-out that failed math doing the alignment for
you? If you complain to them (afterwards), the excuse is usually:
"Sorry, must have hit a bump or a curb".
If you find any fault in any of the above methods or have some better
ways,let me know.
Jan
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From: Mark Sirota
Date: Thu, 31 Aug 89 12:46:36 EDT
Subj: Re: Alignment
Another easy way to measure to is, first, get an accurate tape measure at
least as wide as the car.
> 1) Start with a level smooth floor, bounce, tires
> straight ahead, etc.
This is always important...
Now, using the tape measure, measure the distance from a groove in the tire
tread on the left to the symmetrically identical one on the right, at the
front edge of the tire. Do the same for the rear edge of the tire.
(Note that you are assumed to have identical tires on the left and right.
If you don't, you should, for other reasons.)
Using that trig text you just dug out, calculate the angle of toe determined
by the sides of your trapezoid. Note that this only gives you the total
toe, not the individual figures for each side. That means that even if you
set your front wheels parallel, they may not be parallel to the rears...
The technique for checking that is as follows. (This technique can also be
used as a more accurate way of measuring toe, and gives you individual
readings for each side.)
> 1) Start with a level smooth floor, bounce, tires
> straight ahead, etc.
Now, using a plumb bob or some other such device, mark two point on the floor
directly under the center of the car, one near the front, one near the
back. There should be enough points under the car that are clearly under
the center.
Draw a line between your two points. This line marks the centerline of the
car.
Now, draw two more lines parallel and equidistant from the centerline, a
couple of inches outside the tires.
Set jackstands or some similar device directly on one of the outer lines,
and tie a string between them. Try to make sure the string is parallel to
and directly over the line on the floor, and it should be at the height of
the center of the wheels.
Measure the distance from the string to the wheels, at the front and at the
back edge of the wheel. Use a square to make sure you measure perpendicular
to the string.
You should find that the average distance of each front wheel from the
string is equal, and that the average distance of each rear wheel from the
string is equal.
These sorts of descriptions are hard in text; a picture would be worth a
thousand words. I seem to remember an article on this in VW & Porsche or
Auto-X or Sports Car a few months ago... Anyone else remember that? Maybe
I can dig up the issue and let you know, so you can find it at your library
or something.
> There are tools to do some of these things (like this bubble thing to
> measure the camber) but they are probably too pricy for the casual user. I
> can imagine that there are several more schemes of measuring things, all
> probably requiring more sophisticated tools (which you could make yorself).
I have seen toe and camber measuring devices sold by Hand's Solo, which are
$40 to $50 a piece. The toe device only gives total toe.
I have also seen a handmade toe device, which acts similarly to the tape
measure method I described above. It was a very long rod with calibrations
and slidable, lockable pointers on it. You would stick the pointers into
the tread on the tires at the front edge, and lock their position on the
bar. Then, you would do the same at the rear edge of the tire, and note the
difference. Here's a poor picture:
| |
===|====================================================================|===
You could slide the pointers along the bar, and lock them in position with a
thumbscrew. the bar had graduations along it so you could see exactly how
far apart the pointers were. This is much more unwieldy than the tape
measure, and probably not a whole lot more accurate.
Mark
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Subj: Re: Alignment after front end work
From: Mark Shaw
Date: Tue, 22 Sep 1992 22:53:46 GMT
I no longer bother to mark anything after changing front end parts or
struts --I just re-align the wheels myself. Before I got a tool for
camber measurement ($90) I used to use some shims and a simple 12"
carpenter's square with a bubble level in one leg:
1) Make sure the car is on level ground and roll it forward and back at
least one revolution of the tires.
2) Loosen, but do not remove, both the top (eccentric) and bottom (clamp)
bolts at the bottom of the strut to be adjusted.
3) Place the square with the bubble level horizontal and one end
resting against the lower wheel rim and the other end resting against
the upper edge of the wheel rim. Note that the contact points do
not have to be on opposite sides of the rim, just one point above the
other on the rim edge and in a near vertical line.
4) Now pivot the square away from the upper rim (or lower) contact point
while keeping the other end touching the rim until the bubble in the
level is centered.
5) Use small shims to fill the space between the end that is away from
the rim.
6) Measure the thickness of the shims and convert to degrees (each 1/16
inch is equivalent to 0.3 degree of angle when using a square that is
12 inches long. (or 1 degree = 0.2 inches)
7) If the gap between the rim and the square is at the top - you have
negative camber and if at the bottom you have positive camber.
8) Adjust the upper eccentric bolt to correct the angle to desired
amount.
9) Recheck your camber angle using (3-7) above. Correct again if
needed. Then tighten the two bolts firmly.
10) Recheck angle again. Things can move as you tighten the eccentric!
11) Do the other wheel.
12) Jack up each wheel and take it off.
13) Tighten the two strut bolts to the correct torque (usually around
55 foot-pounds) since it is pretty hard to get my torque wrench
into the wheel cavity.
14) Put the wheels back on and test drive.
The nominal wheel camber is about zero (maybe a little positive), but both
wheels should have the same amount within 0.5 degree of each other.
Since you know what angle you want you can make up the right thickness shims
before you start and have someone hold the square and the shim while you
adjust the eccentric bolt until the bubble is centered in the level.
If for some reason the camber was originally pretty far out of whack, you
may also affect your toe-in alignment as well. I also bought a gage for
this ($30), but used to measure it with a ruler across the back of the wheels
from the center of the tread to the center of the tread (looked for a
groove that ran straight around the tire). Then I measured the same way at
the front. The front should be about 0 to 1/8 inch longer (toe-out).
This is adjusted with the single adjustable tie-rod on the passenger side.
FInally you may have to remove the steering wheel and turn it a few degrees
so that it is lined up level when driving straight.
THE ABOVE METHODS ARE NOT DEAD ACCURATE FOR ALIGNMENT AND WILL NOT CURE A
CAR WITH BENT CHASSIS OR MISALIGNED REAR AXLE, BUT IT IS USUALLY SUFFICIENT
FOR GOOD TRACKING AND TIRE WEAR.
About changing struts ...
I keep seeing people try to disassemble the struts themselves; and cannot
figure why. I usually take mine off the car and go down to a good
tire/brake/shock store and they will disassemble them and rebuild with your
parts for about $10-20 per unit. Sure beats buying the special compressor
and strut wrenches and the risk of failure. Also they use a air impact
wrench which gets the strut properly torqued on reassembly. This is just
one job I don't think needs to be done at home (unless you have masochistic
tendencies!).
(And before someone asks.... I spent $120 on alignment tools because I change
my alignment several times each year for various autocross setups on two cars).
Mark
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Date: 14 Jun 1993 15:40:26 GMT
From: Tom Leone
Org: Ford Motor Company Research Laboratory
Subj: Do It Yourself Alignment
Thanks for a great article! I've done this myself only a couple
of times, but I have a few suggestions:
1) It is easy to do toe-in without finding the true centerline of your
car. Simply check the service manual for the "track" dimension for
front and rear (track is how far apart the outside edges of the tires
are, basically). Set up your string by measuring between the front and
rear wheel hubs. If the front track is wider, then the front wheel hub
should be closer to the string by half the difference in front and rear
track.
2) After you make a toe change, you should bounce the car, roll it back
and forth, and re-check the measurements. I've noticed significant
changes after doing this, probably due to tire deflection. When you
make a change on one side, the tire flexes, which puts enough force on
the steering rack to change clearances and/or flex the other tire. This
might not be a problem if you do both sides at once. I don't think that
locking the steering wheel is sufficient, because there is slop in the
linkage.
I posted something about this on rec.autos awhile back. I'll
append my old article to this one. I've already modified it to
include your suggestion about checking wheel runout!
Tom Leone
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I'm only going to cover the difficult part of an alignment:
measurement. I will assume that you know the basics (which nuts
and bolts to manipulate, etc.). Also, you should make sure that
the wheels are "seated", by rolling car forward and back, and
jouncing up and down. Also, of course, everything should be
done on a level surface (check with a "bubble" level). You
should also check your wheel rims for runout; if the runout is
significant, mark opposite places on the rim where the runout is
the same, and measure at those places.
The key to my method is recognizing how accurate you must be.
On my car, the tolerances are a few tenths of a degree. If your
wheel diameter is about 15 inches, that means you must measure a
displacement of the rim of 15 inches times the tangent of a few
tenths of a degree. That's 0.052 inches (for 0.2 degrees), or
1.33 millimeters. I use a clear plastic ruler (with millimeter
markings), which I believe gives me an accuracy within half a
millimeter.
Start out with the camber. Simply hang a plumb bob (a weight on
a string) over the fender. The string should be right in front
of the wheel hub. Measure the distance between the string and
the wheel rim, at both top and bottom of rim. Subtract the two,
and divide by the distance between the two measurement points.
Take the tangent, and you have the camber (in degrees or radians
depending on your calculator).
After adjusting camber (and re-seating wheels each time), you
can adjust toe. The concept is exactly the same, but this time
gravity doesn't help you straighten the string. You have to get
the string parallel to the car before you can start measuring.
First, stretch the string between two jackstands, washer fluid
bottles, or whatever puts the string at the height of the wheel
rims. Then measure the distance between the string and each
wheel hub (front and rear). If the front and rear "track" are
the same, then the two distances should be the same (track is
the distance between the left and right tires on one axle, and
can be found in your service manual). If the front track is
wider, then the string should be closer to the front hub, by one
half the difference in front and rear track. Double-check that the
strings are the same distance apart at front and rear.
If this sounds confusing, just think it out for yourself. Just
remember that the goal is to get the string parallel to the
car. After the string is parallel to the car, follow the same
procedure as for camber (measure between string and rim, at both
front and rear of rim, divide by rim diameter, and take
tangent). Note that some manuals specify total toe (left plus
right).
After checking toe, bounce the car, roll it back and forth, and
double-check the measurement. It often changes because the tire
was flexed after you made the last alignment change.
Have fun, and please let me know if you have any questions, and
how well it works for you. I've only done it this way twice, but
I think it works well.
Tom Leone