On Mon, 29 Apr 2019 20:00:32 -0000 (UTC), "Arlen G. Holder"
wrote:

On Mon, 29 Apr 2019 11:05:44 -0700, Sanity Clause wrote:

Should I mention that traditionally the red spot is the "high" point of
the tire, and would match with the "low" point of a slightly-not-round
wheel, and the yellow dot is the "light" part of the tire, and matches
with the "heavy" part of the wheel, usually where the valve is? Nah,
that would be mean.

Hi Sanity Claus,

I appreciate those comments, where, if you have a cite that backs up your
belief system, I think it would be useful to all, as Usenet is designed to
be a potluck picnic where each person adds value where they can.

Without further cites, I'd just note offhand that we have a looooooooong
thread on a.h.r, as I recall, on this topic of exactly what the red and
yellow spots mean, which can be _different_ for each manufacturer (and
which aren't always there).


IF thare there, they virtually ALWAYS have the same meaning - and
thee cheaper the tire the more critical it is. (in other words- HIGH
QUALITY tires don't have significant runout - OR significant
inballance. - so the significance of the match marks is less.
For example, we've covered that the marks are generally most useful for
brand-new wheels (where the original match mounting marks are still
visible), and we've covered why the light spot is still generally the valve
area (all else being equal, of course), even though there's an "additional"
valve there, simply because the plug of missing steel is generally heavier
than the rubber & brass valve despite the very many old intuitive wives
tales to the contrary.

I'm all about facts, where we've looked at the cites in the past to
conclude that, in the absence of match-mounting marks on the wheel, the
best course for a starting point mount at home is the red spot goes next to
the valve if you have a red spot, and if you have only a yellow spot, as I
recall, it goes opposite the valve (but I'd have to dig up the cites to
doublecheck on that as most tires I've mounted have both the red and yellow
so I only use the red mark as my starting point).

The yellow spot is the LIGHT spot of the tire - the red spot is the
point of MAXIMUM radial rounout - so you want to use the YELLOW spot
as your reference if there is no rim match indicator. Then it is up to
you to decide if you think the valve (metal or rubber) has more
inertial weight than the slug of metal missing from the rim, and
position it accordingly. Either way, the difference is pretty small -
but MIGHT make the difference between needing a 1/2 ounce weight and
not needing any at all.

In summary, if you can back up your belief system with a cite, I'll read
it, and if you want, I can dig up cites that back up my belief system since
my belief system is never imaginary - my belief system is _always_ based on
actual facts.

If facts show I need to _change_ my belief system, then I'll change it.
o But at the moment, the facts show the red dot goes next to the valve
(for stock steel wheels, and for most manufacturers' tires)

https://www.motor.com/magazinepdfs/042008_09.pdf

Note IN PARTICULAR the botton left of page 38 and top right of page
39:
- If a tire does feature color dots on the
sidewall, one or two dots may be used.
A red dot indicates the tire’s radial runout high point. A yellow dot
indicates the tire’s point of least weight,from a balance standpoint.

It also states:

For decades, it was common practice
in the aftermarket to mount a tire so its
red dot aligned with the wheel’s valve
stem, since the valve stem area was normally
assumed to be the wheel’s lowest
point of radial runout. Aligning the tire’s
high point to the wheel’s low point (theoretically)
reduces or eliminates the
chance of developing a radial force variation
(RFV) in the tire/wheel assembly.
RFV (again, an issue of runout, not imbalance)
can cause a vibration that
might be mistakenly diagnosed as an
imbalance problem.
Times change. With the advent of
styled custom wheels, the valve stem location
may no longer indicate the
wheel’s low radial runout spot. In other
words, it may no longer be viable to assume
that aligning a tire’s red dot to the
wheel’s valve stem will address any potential
RFV issues.
Consequently, a procedure that was
once easy has now become complicated.
The only way to accurately matchmount
a tire to a wheel is to actually
measure tire and wheel runout. The end
goal remains the same: to align the tire’s
high point to the wheel’s low point. The
wheel itself can be easily checked for radial
runout by mounting it to a hub and
slowly rotating it while monitoring the
rim edge with a rigidly mounted dial
gauge.

If you have facts that show otherwise, please cite them so we all benefit
from every post.