On Thu, 27 Jun 2019 19:09:03 +1000, Xeno wrote:

Yes. It depends on how the manufacturers set up their cars ex factory
and what they have in the specs. It has to be said too that a lot of
people wouldn't know the difference between positive and negative. Have
you looked up the actual specs for these cars?

Hi Xeno,

I don't know the specs, but they're all high end vehicles such as this
Lexus SUV https://i.postimg.cc/G3HWPtQg/mount39.jpg or this BMW SUV
https://i.postimg.cc/g004XCLW/mount37.jpg

FWIW, FWD cars tend to be
a little different because they *drive* the front wheels.

Very few seem to be FWD - most seem to be RWD or AWD like the X5.

Also, a car
with struts is going to get less camber roll under weight
transfer/suspension jounce. Because of this, they may start at less
camber, even 0, and then have a limited movement into negative
territory.

A few have reported high negative static camber, but, as you noted, a lot
don't know offhand what the camber is - but none who have reported have
said it was ever positive.

Different suspension types have different sets of compromises
and you need to look at the specs of each car in terms of suspension
type and drive arrangement.
Look at this one for example. https://i.stack.imgur.com/HnEJq.jpg

Notice though, that those Avalons are _all_ negative camber setups.
It doesn't seem that any cars (yet) have the Bugatti style positive camber.

Focus on the Camry 4 cyl spec - it's -0.72, not a range, just a
preferred setting. They just give a tolerance on top of that. The
tolerance is +/- 0.75 so you could have the camber set to anywhere
between 0 and -1.5 degrees of camber, noting that the higher your static
camber goes, the more likely you are to have camber wear issues in
straight running...

Notice though, that it's always negative (so far) camber, which seems to be
what I need to assume, since I'm asking for help solving a systemic problem
in hundreds of cars now that you've helped me identify the primary issue:
o Low speed camber scrub of the outside edge of the inside wheel
https://i.postimg.cc/8zVxVHVx/mount40.jpg

made worse with wider tyres.

Ah! Nobody talked about the width of the tires yet!

Are you saying that the low speed camber scrub of the outside edge of the
inside front wheel is worse with width? If so, that's one possible
amelioration, albeit there isn't much of a range that one can choose in
tires that's practicable.

If you look at the SAI,
it is close to 12 degrees - at the top end of SAI specs. That means this
car will be less reliant on caster for self centering of the steering.
The caster settings at what appears to be 0 +/- 0.75 seems to point to
that. Certainly, at a zero setting, caster won't be doing much to
influence steering self centering and, it has to be said, won't be
worsening the effects of camber roll.

I get your point that positive caster is likely the most important to
lower, where, within range, it's the most bang for the buck.

Your road is more than cambered, it's superelevated, that is, the road
has a cross slope on its full width. This not only assists drainage but
helps vehicles round the curve, the cant assisting the turning vehicle
even at slow speeds. We have a severely off cambered roundabout here
that regularly catches trucks out. Saw a tanker over on its side
recently when the driver misjudged the curve.

In general, the bigger trucks have to back up a couple of times to make
most of the curves, where in some of the curves, the trucks dig into the
roadway, as you could see in that photo.

You can vary the caster slightly to compensate for the crown, at least a
*normal crown*. A little more on the nearside perhaps. Roads, in this
country at least, aren't crowned like they used to be. Your pics show a
huge cant in the road to the inside of the curve which would put
pressure, at slow speeds where cornering inertia has less effect, on the
outside edge of the inside wheel which is already positively cambered to
the extreme.

Unfortunately, I didn't snap any photos of the width of the road, just the
corners.

It's nighttime here, so tomorrow I'll look for this "cant" in the road that
you speak of, as I'm not sure I understand what you're trying to tell me as
for its effect on the camber scrub of the tires.

CANT: https://en.wikipedia.org/wiki/Cant_%28road/rail%29
https://howlingpixel.com/i-en/Cant_%28road/rail%29
SUPERELEVATION: http://www.dailycivil.com/superelevation-of-road-advantages-design/