On 27/6/19 3:46 pm, Arlen G. Holder wrote:
On Thu, 27 Jun 2019 14:13:38 +1000, Xeno wrote:
That is precisely what I have been saying, drop the caster.
Hi Xeno & Clare,
One thing that I shouldn't be confused about, but that I am, is that most
people I asked said they had NEGATIVE front and rear camber.
NOBODY said their static camber was positive.
Does that make sense?
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? FWIW, FWD cars tend to be
a little different because they *drive* the front wheels. 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. 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
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, made worse with wider tyres. 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.
Also, if you look at the road, it has a high'ish crown, given that it's
never flat even once since it's a long five miles of twisty mountain grade.
https://i.postimg.cc/pX44ffQB/mount46.jpg
It's so steep in mosts places that trucks literally run off the road or dig
INTO the road, surprisingly:
https://i.postimg.cc/pX44ffQB/mount46.jpg
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.
Two thought questions about the CROWN of the steep twisty road:
1. How does the crown affect the customization of alignment for tire wear?
https://i.postimg.cc/wxf5CyS6/mount42.jpg
2. Is the crown part of the wear problem (we haven't mentioned it yet)?
https://i.postimg.cc/kGhZh80q/mount44.jpg
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.
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)