Bronco
TTB Front Wheel Alignment
For the do it Yourselfer if You Want it Done Right
The following procedure, methods, spec’s, etc. are what I used to achieve an alignment I believe to be acceptable. It seems to have worked for me in that with camber, caster and toe within spec, and unlike before, the vehicle no longer pulls neither left nor right at highway cruising speed on a level road in good condition.
I make no guarantee or claim that this will produce an accurate or acceptable alignment. If you choose to give it a try it is wholly at your own risk.
Procedure:
1) Park vehicle on solid level surface.
2) Relieve suspension preloading due to lateral tire forces by lifting each side to break tire/ground contact and then lower back down. The jack must be placed at least as far outward as the spring. This step may need to be repeated several times during the alignment process.
3) Measure side to side ride height and adjust if necessary by redistributing the load or add/remove load to/from the vehicle.
4) Set the toe to be reasonably straight. It’s not important to be exact at this time.
5) Measure camber and caster.
6) Raise wheel and make adjustments.
7) Repeat steps 2 through 6 until the desired camber and caster are achieved.
8) Make the final toe setting adjustments.
Spec’s:
’89 F-150; ’96 Bronco
Min.
Max.
Camber*: -0.3°
+0.8°
Caster*:
+2.0°
+6.0°
Total Toe*:
-0.19° +0.31°
Ride Height:
within 3/16” side to side.
* According to alignment computer system at a well known chain of tire shops
in the northwest.
Measuring the camber, caster and toe can be done many ways. Here are the methods and tools I used.
Camber:
To measure the camber I used a plumb bob line from the top of the wheel to
the bottom of the wheel. On a
15” wheel 1° is 0.131” (approximately 1/8”).
When measuring across the entire wheel this distance is double.
So a difference of 1/4” from top to bottom of a 15” wheel would be
approximately 1°. Used the same
method for the rear wheels but have no spec’s.
Caster:
To measure the caster I used a straight piece of 3/4” square tubing
about 24” long and sandwiched it between the flat surface below the upper
ball joint and axle shaft u-joint. Then
took two measurements along the tubing about 15” apart.
Using rise over run an angle can be calculated.
So long as the caster is within spec the most important thing is for
the left and right to be close to the same.
A little more on the right will push the vehicle to the left and
correct for the crown in the road. When
my ’89 F-150 was aligned on a computer system they set the right caster at
0.53° more than the left. That’s
about a 1/8” rise over a 15” run by my calculations.
Toe:
The toe was measured with an ordinary tape measure between the left and
right wheels at the forward edge and the rearward edge of the wheel, and set
as close to 0° as possible. Erroring
toward being toed in rather than toed out.
But definitely no more than 1/16”.
Used the same method for the rear wheels but have no spec’s.
Ride Height:
Ride Height is measured from bottom of spring/shock tower to axle.
Frame Square:
To check for frame square, using a plumb line bob transfer the frame
alignment peg locations to the ground. Then
measure the diagonals. I have no
tolerance spec’s.
Rear Axle Square:
To check for rear axle square with the frame I measured from the rear
frame alignment pegs to the end of the axle tube on each side.
I have no tolerance spec’s.
Tools:
Torque Wrench
1-1/8” Socket
1-1/8” Box/Open End Wrench
Snap Ring Pliers
Medium Flat Blade Screwdriver
2 to 3 lb. Hammer
Tape Measure
Plumb Line Bob
24” x 3/4” Square Tubing
Jack
A person could probably also make some low friction pads for under the front wheels with some steel plate bordered with angle iron, filled with BB’s or some ball bearings and oil/grease, and a round piece of steel plate on top. Then you wouldn’t have to raise the vehicle to relieve the suspension preloading. Just a thought.
Here are some additional possible measurement methods and tools that were suggested to me by others.
Jason
Lockwood
Make a
couple of big squares, similar to framing squares, do a little trig and
determine what 1 or 2 degrees of camber looks like at the wheel (NOT the tire,
tires bulge at the bottom) and load the vehicle up to simulate you as a driver
and whatever passengers/gear you typically carry and buy a set of adjustable
ball joint sleeves if you don't already have them.
For
caster, Sears and Harbor freight both sell little pendulum style angle
finders. They're not as accurate as a proper alignment machine because the
graduations are too close together, but they're good enough for a rig that has
a front axle that changes alignment by several degrees as you drive it.
I don't know on the TTB if there's a good place to measure, but the caster is the angle viewed from the side that the upper ball joint is behind the lower ball joint. On a solid axle, there's a nice machined shelf in the knuckle just inboard from the lower ball joint that a straightedge can rest on. Then the angle finder can sit on the straightedge.
If there isn't a good spot like that on the TTB knuckle, then I'm not sure what to suggest.
With big tires, a caster setting of around 6 degrees seems to drive fairly well. Going over about 8 or 9 can make it susceptible to wobbling and going closer to zero reduces the self-centering effect of the steering wheel. Scouts came with zero caster from the factory. It makes them have a nice light feel to the steering when off the road, but doesn't improve the high speed handling much.
Most important thing on caster is to make sure the two sides are close to the same. That makes them cancel each other out and makes it track straight when on level road. If you can't get them the same, a little extra on the right isn't a bad thing to help counteract the crown on the highways here in the northwet.
The biggest thing to watch out for on a TTB is to make sure that after you do an adjustment, you need to drive it around a bit and gently roll it to a stop to make sure that the contact of the tires with the ground isn't preloading the tire sideways and giving you a false reading. If you jam on the brakes, the front will squat and the camber readings will go negative. The tires will spread out at the bottom and when you let off the brakes after you stop, the traction of the tires holding the bottom out will keep the caster in a negative condition and will keep the ride height artificially low.
Mark
Zoelch
You can do an OK job of determining camber on the TTB. I use a
sears degree finder tool (why can't I remember the name of that thing?)
I put it against a straight edge and run the
straight edge vertical over the entire tire, BUT as Jason says, NOT the
center of it, because at the bottom it will bulge. You can get an
accurate
enough reading with this down to within a degree. I am able to determine
with this method that I run right about 1 degree positive camber, which is
a bit more than I really prefer. If you run it over the bulge, the
reading
will be off easily by several degrees.
Chris
Samuel
Get a piece of 1.5" minimum steel angle iron about 18 inches
long.
Measure the distance from the face of the rim on one side to the same spot on
the other side of the wheel. This should be inside the lip of a steel
wheel.
Drill
two 1/4" holes in the angle iron centered on the angle iron at the above
measured distance.
Screw
in two 1/4" bolts and nuts (2 nuts on each bolt) so that you can use one
nut on one side of the angle iron to adjust the distance that the bolt sticks
out from the angle iron, and the other nut on the other side to lock the bolt
in that position. Set the bolts so that the angle iron is held off of
the
wheel and clears the tire. Set the bolts to as close to the same length
as you
can, exact would be good.
You
now have a repeatable surface that you can take from one side to the other
and measure the camber angles. Using two angle finders is a good idea:
one
makes sure that the angle iron is vertical, and the other measures the Camber.
You can modify this tool to pick up two points one the knuckle to directly
measure the Caster.