Hello Zoro!
I am Ward Zintel, Priya's husband. I am an automotive technician, and I do a
lot of chassis work and wheel alignments (my speciality).
Right off the top I suspect you have an issue with the toe on the vehicle,
radial tires do not wear the edges from camber unless they are very low profile
tires, like a 40 ratio (PXXX/40RXX) tire or lower, not the type of tire likely
to be on a 4WD/AWD vehicle.
If you take you hand, palm down, and slide it in and out on the tire (towards
the center of the vehicle and back out) - do this in a spot with no steel belts
showing, the belts will chew your hands up, don't ask how I know this! If the
inside of the tires is worn away the tire will feel smoth sliding out, and rough
sliding in. If it has this it is "sawtooth wear", caused by the toe being out of
specs.
priya's eagle service manual gives ball joint specs of .160" laterally (side to
side) for the upper ball joint and 0(zero) play on the lower ball joint, any
visible play is grounds for replacement. I recommend blocking a piece of 2X4 or
something similar between the bottom of the upper control arm and the frame so
when you jack it up the control arms remain in roughly the same area they are in
with the wheels on the ground as this is where most of the wear will be.
Give the control arm bushings very close scrutiny, they are rubber and will
move but should spring back, if they have enough play to slop around they will
let thecontrol arms move about , causing the toe to change constantly, and too
much.
If any parts are bad, get them replaced, and back on the alignment machine.
Find a shop with a modern computerized 4 wheel alignment machine. Tell them you
want a print out, with the following readings:
-Front caster, camber, and toe. These are the normal front alignment angles, the
"basics"
-Rear camber, toe, and thrust angle. These readings will tell you if your axle
housing is bent, and how it's located under the vehicle. Rear camber ideally
should be within .25 degree of zero, but I've seen solid axles with .5 degree
negative camber that worked just fine and did not wear tires. Ideally the total
toe on the rear axle will be with in 1/8" of zero (zero preferred), if it gets
more than about 1/4" it'll start wearing the rear tires. The thrust angle should
be with in .5 degree of zero, if it's more than that the axle is not tracking
correctly, causing the car to "dog track"
-Front and rear setback. These readings tell us where the tires are located
relative to each other, and along with the thrust angle and a couple more to
follow, allow us to find accident damage. Setbacks should not exceed .5" side
to side on either axle.
-SAI (or KPI) steering axis inclination (king pin axis inclination). this is a
very important angle to get, it's the angle of an imaginary line drawn through
the ball ball joint pivot points reference to true vertical. If possible, have
them get you this measurement wheels elevated, it's more accurate this way.
-Icluded angle. This angle is though the ball joints like SAi, but is referenced
to the plane of rotation of the wheel, instead of true vertical. Once again have
this measurement made wheels elevated.
-The SAI and included angles, taken together with the front camber allows us to
find bent suspension components (steering knuckles, control arms, body mounts,
etc). In an ideal universe the sai, included angle,
and front camber will all be within .5 degree of the same angle on the other
side of the vehicle, but there is much more to it than than that, as the
universe is not quite that ideal. When you have some readings I will gladly
look at them and let you know what I see.
-The last reading to get is the toe out on turns reading. They also should be
within .5 degree of each other, the closer to the same the better. I have seen
vehicles with close to a degree difference side to side that did not wear tires,
but it's not ideal. If these readings are much more than .5 degrees diferent it
indicates a bent steering arm.
Clear as mud, eh? If you have these readings let Priya know, I'll gladly tell
you what I see. -Ward-
Topic: Eagle keeps eating thru front tires, multiple alignments haven't helped (Read 10968 times)