On Thu, 13 Jun 2019 20:28:17 -0000 (UTC), "Arlen G. Holder"
wrote:

On Thu, 13 Jun 2019 17:11:14 +1000, Xeno wrote:

You can check the camber all you like but the answer is more likely in
the SAI angles and you will be able to do SFA about that.

Hi Xeno,

Thanks for your purposefully helpful advice on kingpin inclination angle
(aka steering axis inclination), and perhaps included angle, neither of
which have I delved into yet (as I'm starting with camber, which is the
basis for caster calculations, and where toe is relatively simple).
http://www.valleyofhastings.com/WheelAlignment2.pdf

Other than Clare, you and maybe one or two other folks here are
knowledgeable in the important details of home alignment checks &
adjustments, where I don't usually disagree with anything you guys say, as
you know more than I do.

We have to remember a home DIY alignment check & adjust is sort of like
doing a DIY tuneup versus a complete engine overhaul
o A DIY caster/camber/toe check/adjust is to a professional alignment
o as a DIY tuneup is to a professional engine blueprinting overhaul

The fact is that the SIA is a "non adujstable" angle:
https://www.freeasestudyguides.com/included-angle.html

The fact it's not adjustable means it is in a different category than
o caster
o camber
o toe

While SIA is not normally adjustable, looking this up anyway for more
insight, it seems SIA checks generally simply need yet _another_ magnetic
bubble gauge, much like the camber gauge apparently, but offset by 90
degrees, according to this cite:
o Checking the Steering Axis Inclination Angle
http://route66hotrodhigh.com/Inclination.html
Which says:
"To measure steering axis inclination, the method is identical to caster
measurement except that you use the steering axis inclination guage [sic]
which is at a 90 deg angle to the caster gauge. The wheel is turned 20 deg
inward. The steering axis inclination gauge is centered for 0 deg caster.
There is an adjustment screw on the back of the gauge that allows you to
set it for 0 deg. The wheel is then turned to 20 deg outward for a total
movement of 40 degrees. The steering axis inclination angle is read off the
gauge."

The key question is where to get that SIA gauge, which, apparently, can be
replaced with a normal magnetic caster gauge according to this patent:
o Device & method for measuring SAI on a steerable wheel (#4,546,548)
http://www.freepatentsonline.com/4546548.pdf

In short, if we're aligning a vehicle that we own and drive often, then we
don't have any reason to suspect SIA changes (which will only occur with
bent or worn parts), and hence, they aren't part of what typically changes
(which is caster, camber, and toe).
https://www.motor.com/magazinepdfs/062002_05.pdf

about type of use instead. If it is all city and suburban driving, tyre
wear on the outside of the tread can be considered 100% normal.

On this mountain, everyone wears tires sooner than people who drive in
flatland do, where there is just "something" horrific about five miles of
steep driving,

I'd be cranking in a couple degrees of negative camber for extensive
downhill twisties. And running about 36PSI minimum pressure in the
front tires.

Most seem to wear on the outside edge, which I still haven't figured out
exactly why. The road is about 5 miles at about a 9 percent angle with very
many 180 degree and even 270 degree switchbacks, but the speeds are rather
slow, where the road is too narrow to even have panted centerlines and
where the nominal speed limit for such roads is 25mph.

Given nobody drives 25 mph anywhere, we can figure it's something like 30
mph to 40 mph top speed but there's a lot of braking in between. Me? I just
put the tranny in neutral and roll down the entire five miles by giving up
potential energy, where I only brake when I must and I take the turns very
wide (as most people do) which helps maintain speed.

Somehow, _that_ process (which most people do, I think, but in gear most
likely), wears tires out like you can't believe, where tires get half the
stated mileage, as far as I can tell by aggregate conversations.

Turn the wheels to a high level of lock and the obvious will confront
you. The type of feathering will tell you what the actual cause is.

I do admit that I can't 'read' a tire very well. I've tried, but rotations
screw up the readings, and certainly there can be multiple causes.

The type of feathering I mostly see is the kind you can feel after only
about 1000 miles on the outside edge, for about 3 inches of tread, where
there is a sharp lip that is feathered into that outside tread that you can
only feel moving your hand clockwise over the front tire tread on the
outside 3 inches.

I need to learn more, but I think that's "normal" since it happens even
after I get a professional alignment. I'm due for one soon for a couple of
cars, which is why, instead of paying the $150 per vehicle, which for the 3
cars I want to do first, will be almost five hundred bucks, I'd rather buy
the tools to do it myself for that same five hundred bucks.
o Caster gauge (to measure caster & calculate camber)

You got that backwards - - - - You MEASURE camber and calculate
caster (unless you have PROPER equipment which measures both)
o Caster jig (to lock onto the wheel for the caster gauge to be accurate)
o Wheel plates (to move the wheels for adjustment under suspension loading)
o Toe plates (to enable single-person linear measurement to centerline)

After having discussed this with Clare in the past, I know we can redneck
some of that, but overall, those four items seem to be the key items needed
for a home DIY check/change of caster, camber, & toe, do you agree?


It might take a REAL PRO to modify the camber properly likely require
installation of either camber plates or long lower control arms (or
offset bushings)