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3/21/2018 8:02 PM  #1


DIY Home Alignment

I did an alignment on my 65 FB, so I thought I'd do a write-up on it.  I don't claim this is the best way, or the fastest way - just how I did it using a simple jig I made.  A few initial considerations about my car that made this a lot easier:
 
(1) It has my DIY adjustable strut rods (see my other tips post on them).
(2) I welded on Opentracker's lower control arm kit, which in addition to a screw-in ball joint and lower reinforcing, has a spherical bearing in place of the rubber bushing.  The spherical bushing removes any worry about using the adjustable strut rod exclusively for caster, as the spherical bearing won't bind like the rubber bushing may do.
(3) When I installed the upper control arms, I spun the shaft forward, moving the upper control arm toward the back of the car for improved caster, per Daze's write-up here: http://dazecars.com/dazed/UCA.html.
(4) I installed Opentracker's lower control arm camber kit, which allows camber adjustment through the use of different offset mounting positions for the lower control arm attachment.

Because of these mods, I was able to set camber and caster without any shims in the upper control arms.  The lower control arm camber kit produced a camber of -0.4 degrees on one side and -0.3 degrees on the other side.  All caster adjustment was made with the adjustable strut rods, producing +3.0 degrees on both sides.  A toe-in of +1/8" was done using the jig I describe below.  Here's a picture of the jig:
 http://i67.tinypic.com/r8z7eh.jpg

Here's another view:
 http://i65.tinypic.com/2n735hh.jpg

I made this jig to fit my 17" rims.  It's possible to make the jig universal via multiple holes or sliding mechanisms, but I didn't bother.  The upright is 1" square steel tubing 17" long.  The cross bar is 1" aluminum angle 36" long, but it could be cut down to 30".  The cross bar is attached with a couple of 3/16" pop rivets that you can see in a photo below:
http://i63.tinypic.com/i6z634.jpg

Three 1/4" bolts center the jig on the rim, with plastic acorn nuts to prevent scratching the rim. The jig is held onto the wheel using bungee cords.  A magnetic angle cube attached to the steel square tubing to read the angle of inclination:
http://i64.tinypic.com/73oyfl.jpg

The bolts on the jig are adjusted so that if the jig is laid bolts down onto a level surface, the square steel tube is also level.  This, plus leveling the floor on which the car sits are key considerations in getting an accurate alignment. 

I leveled the floor by driving the car into my garage where I was going to do the alignment.  I then marked each tire with some tape:
http://i63.tinypic.com/24bqo8l.jpg
 
Then, I drove the car back out and proceeded to level the area around each tire.  As a first step, I had to consider the thickness of my turning plates for the two front tires.  For each turning plate, I used two linoleum tiles with a bit of grease in between (which worked out very well).  I stacked two tiles on each of the front spots before shooting the elevations.  I shot the elevations  by setting a laser level on a level spot in the center of those four marked areas and then using a block of wood as a target (a dark room helps to see the laser).  This laser level produces a cross which is very handy):
 http://i63.tinypic.com/2zeaxyg.jpg

Here are the results:
 http://i64.tinypic.com/24fl9p5.jpg

As you can see, the upper right spot was the highest (1-3/4"). The lower left spot was the lowest (2-1/2").  The lower figure in each of the above boxes is the spacer thickness needed, which is arrived at by subtracting the highest elevation (1-3/4") from each of the other three.  I cut spacers from 12" square plywood to match the linoleum tiles used for the turning plates.  I then drove the car back onto the same areas and jacked up each wheel to install the turning plates and spacers.  If you try to drive over the greased turning plates, you'll make a mess, and the spacers shoot out even when hot melt glued to the floor, as I found out.

Since my car is just getting finished from a complete rebuild, it hasn't had an alignment since a new front end was installed.  Because of this, I wanted to set the front wheels to zero toe as a starting point.  I did that by installing the jigs on the rear wheels with the laser level on the aluminum cross bars in order to shoot a laser line forward to a target next to the front wheels.  I set the steering wheel straight ahead and then equalized the measurement to the front and rear of each of the front rims, while ensuring that the length of the tie rods were as equal as possible.

The next thing I did was to check camber, setting the jig up on the front wheels:
http://i66.tinypic.com/2wlt2k8.jpg

The wheels were straight ahead from the previous step, so I used tape to lay out a line parallel to each wheel.  If you're really picky about alignments, those lines should be parallel to the thrust line of the car, which I didn't bother to lay out this time.  Two additional lines were layed out at plus and minus 20 degrees (more on that later).  I leveled the jig's crossbar using the bubble level on the laser level.  Note that the magnetic angle cube is attached to the square steel tube at about 90 degrees.  Before doing that, I set the angle cube onto a level surface, turned it on its side to 90 degrees, and then zero'ed it.  At this point the following conditions have been established: (1) the floor is level, (2) the jig's bolts were previously adjusted so its square tube upright is parallel to level, (3) the jig's crossbar is leveled on the wheel, and (4) the angle cube is zero'ed at 90 degrees to level.  Now the jig can measure camber, which in my case was -0.4 degrees on one wheel and -0.3 degrees on the other.  I guess I could have installed a couple of thin shims to try to get both wheels at -0.3 degrees, but that was close enough for me.

Next I set caster by turning the wheel to each of the 20 degree positions, noting the camber reading, and plugging that information into an equation to calculate caster.  The jig is easily lined up with the 20 degree lines:
http://i66.tinypic.com/2qkuosi.jpg


You may have come across this equation in various other forums on how to perform a DIY alignment:

Caster (deg) = (180 / π ) * [(camber1 - camber2) / (turnangle1 - turnangle2)]

Where π  is approx. 3.1416.  The equation is usually explained by stating that assuming a total 40 degree sweep, you multiply the difference in camber readings by 1.43, which is (180 / π )/40.  However, as can be seen by trying out the equation in practice, it matters whether you start by turning the wheel left or right because it's likely that in sweeping the wheel through its 40 degree arc, the camber goes from positive to negative or vice versa.  So unless the two angles are oriented such that they also change sign and that sign convention is used in the equation, a wrong result will be had.

Although not usually cited, that equation comes from an SAE paper entitled, "Steering Geometry and Caster Measurement," by Daniel B. January, Hunter Engineering Company.  That paper is available from the SAE (at a price).  The correct form of the equation is:

Caster (deg) = (180 / π ) * [(camber1 - camber2) / (turnangle2 - turnangle1)]

Also, the turn angles are oriented with respect to the thrust line.  For instance, my taped off 20 degree angles should be viewed this way so they work in the above equation:
http://i65.tinypic.com/icpwzn.jpg

So in the above equation, turning the wheel to the left is +20 degrees, and turning it to the right is a -20 degrees.  Now all the math works out.  For instance, in my case, the final equation was:

Caster (deg) = (180 / π ) * [(1.1 - (-1.0) / (20 - (-20))] = 3.0

In this case, I started with the wheel turned right and "camber1" is positive and "turnangle1" is negative.  The result of the equation is a positive numerator divided by a positive denominator, which of course results in a positive answer.  Had I picked the starting point by turning the wheel left, the result of the equation would have been a negative numerator divided by a negative denominator, which if you remember your Algebra, results in the same positive caster angle.

Regardless of how you adjust caster, your camber will change a bit, so you'll have to check it again.  If you change it, then caster changes, which then .....  However, a couple of rounds of this and the changes become insignificant.

Following caster and camber, I set toe-in at 1/8" by simply measuring across the cross bars, while keeping the tape measure against each side of the tire. I adjusted the tie rods on each side equally.

One change I would make to the jig would be to replace the plastic acorn nuts with some kind of rubber feet, since the plastic acorn nuts have a tendency to slip, causing the jig to go out of level.

Last edited by jkordzi (3/22/2018 9:21 PM)


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