On Sun, 11 Dec 2016 01:07:00 -0000 (UTC), John Harmon
wrote:

Bill Vanek actually said:

Regarding the needed accuracy, it depends on exactly what you are
trying to achieve. There is a wide range in camber that will not cause
any meaningful tire wear.

However, in the end, a "smidge" of negative camber (about a degree or so)
is probably in the accuracy range we really need, which a smartphone can
do.

The old standard was always about +- 1 degree, when you had no other
specs to go by. Enthusiast cars like the BMW have different needs for
handling purposes.

The overall point is that even if you are off with the camber, the
tires are not going to be worn out all that much earlier, so close can
be good enough, especially if you bother with rotation.

BMW does not recommend ever rotating tires,

That's not uncommon.

but they don't care about tire
wear. The camber is only adjustable in the rear and it's pretty high (I
forget but it's at least 2 degrees negative camber for each rear wheel).
That wears out the inner edge like you can't believe.

That doesn't sound right. 2 degrees should not cause early wear, so
you really need to check the ride height. And recheck the camber.

As for wear, it seem everything goes in this direction:
1. caster
2. camber
3. toe

Yes, caster will not cause wear.

In that caster is done first, then camber, and then toe, and in that wear
is least with caster and then more with camber and then even more with toe
(under typical settings).

That's not the reason for the order, but it's not important.

Toe is much
more important, and if you want that exactly right, pay someone to do
it right. You can get it close at home, but it's just luck if it's
exactly right.

I have done my toe when I replaced tierod ends, pitman arms, and idler
arms, and then when I took the cars for alignment, the toe was spot on.

So I think toe is easy, compared to caster and camber.

I hate to say this, but you can get pretty close just eyeballing toe
and camber. Especially with camber, if you can't see any substantial
lean, the camber is probably close enough that it won't cause tire
wear. In a pinch, it works for toe, too.

There
is plenty of slop in steering & suspension, and you will get varied
readings, especially if you are not using turntables. Sometimes trying
to save money is not such a good idea.

The simple test is to set the alignment at home, and then take it to the
shop for double checking.

It's not necessarily a repeatable test, though. The one time you do
that, you might have gotten lucky.

Many shops offer free tests if nothing needs to
be changed; but I would hesitate to take them up on that only because they
can always find something so I suspect that's just a gimmick.

Has anyone here ever gotten the "free test" actually for free if there was
nothing to change? Or do they always find "something"?

They are expected to print out the readings, so it takes some effort
to lie. I'm sure they usually find something, but that's only because
cars do go out of alignment.

At the same time, finding someone to do the job right can be a
challenge, too. There's plenty of hacks out there.

Never in my life (and I'm an old man) have I seen a mechanic install a tire
correctly (I use Tire Rack authorized installers), so I suspect it's the
same with alignment.

For example, I had to bring 500 pounds of my own weights to my last
alignment. The alignment guy *knew* how to do it right, he just knew that
most of this customers don't have a clue.

I'm pretty sure that none of the manufacturers expect techs to load a
car before alignment anymore. The specs take into account average
occupant weights.

It's the same with the tire mounting shops. They *know* how to do it right,
but they also know most of their customers don't have a clue so they get
lazy.

I doubt a single car tire is installed correctly, by the book, on any car
taken to the typical tire shops (wheel works, goodyear, midas, etc.).

And I doubt that it makes the least bit of difference.

If all you care about is getting things close enough that there won't
be ridiculously excessive tire wear, then have at it. But if you are
trying to get things just right, both for handling and tire wear
purposes, pay someone.

I think the summary is this simple.

A. Check the alignment at home for the things that can be adjusted.
For my Toyota, that's only caster, camber, and toe in the front, and for my
bimmer, that's only camber and toe on the rear and toe on the front.

B. Adjust if necessary (using a smart phone or inclinometer for camber, and
a tape measure for toe). I'm not sure how to do caster in the toyota since
I only just found out that the caster is adjustable on the toyota.

C. Take it to one of those "free if it's ok" shops, and see what they get
for measurements.

If I'm perfect, it's free (I assume); if it needs adjusting, then I learn
what can and can't be done.

You don't really learn that, except for each time you try it. You can
get very different results on future attempts.