On Sat, 29 Jul 2017 04:51:12 +0000 (UTC), Roy Tremblay
wrote:

actually wrote:

I'm not saying they WILL separate - but you are increasing the
chance.

I understand what you're saying and I agree with you that it would be very
important if changing the direction of non-directional radial tires causes
a meaningfully valid chance of the belts separating.

I'm not arguing with you aa what you say makes sense.
I am just trying to find reliable sources that back that up or debunk it.

Most source I found say an X pattern is fine, which, unless you remount the
tire on the wheel, results in a change of direction. Almost all the sources
I found said to use what they call the "rearward cross" or the "forward
cross" which also results in at least two tires changing rotation
direction.

All I'm trying to do is find reliable sources to better explain the risk of
reversing the direction of non-directional radials.

Look at how a steel belted radial tire is built, then envision
how the belt works into the rubber carcass and takes a "set".

I have many times heard about this "set" which seems to usually be
mentioned with respect to radials. If this set is real, it can easily be
envisioned to be from both road crown being consistent and camber being
consistent for a period of 4000 miles.

Now, reverse the rotation, and see what the steel belt tries to do. It
tries to "take a set" the other way.

Yep. Makes sense.

In doing so, IF IT SUCCEEDS, the
belt will get loose in the carcass, where it will cause heat buildup
as well as weaken the bond between the belt and the carcass rubber.

Yep. Makes sense.

This is particularly dangerous when the rubber hardens a bit with age.

Maybe. But Yep. Makes sense.

Some tires harden more than others - so some are more of a problem
than others.
Even without the rubber getting hard, having the steel belt shift
inside the rubber carcass is never good.If the bond between the rubber
and steel is compromized, the tire comes apart.

Yep. Makes sense.

Running a tire with too low pressure, or significantly overloaded,
causes the same problem with the bond between the rubber and the
steel.

Yep. But different issue from rotation.

On a TOP QUALITY tire you MAY get away with it, but with so many even
American branded tires being thrown together offshore in places like
China, Singapore, Thailand, Viet Nam etc,do you really want to find
out the hard way???

You are right that the goal in rotation is to get the longest life out of
my non-directional radial tires. If the X pattern causes belt separation,
that would be counter productive.

Yet the X pattern (or modified-X pattern) is recommended in almost every
tire rotation article I can find, even those from Goodyear and Tire Rack
and the car magazines.

So if the X pattern is causing treads to separate, why do they almost all
universally suggest an X pattern (or modified X pattern) for
non-directional radial tires?

They sell tires. Does that give you an (al-be-it) cynical) answer?

I am still searching for a good writeup that seems trustworthy but all the
ones I have found so far are more advertising gimmicks than they are
helpful.

Like I said - they sell tires.
I'm not arguing with your premise which I appreciate that you brought up.
I'm just trying to find supporting evidence.

You won't find it in advertizing copy. If you ask 50 mechanics who
have been in the business, not working for tire shops, since the
advent of Radial tires, you will find the majority say "the experts
say it doesn't make a difference, but I never cross rotate the tires
on my own vehicles"

That says something - no?

I have never had a radial tire carcass failure on a tire that I know
has never been cross-rotated or run too low on pressure. The only
carcass "failure" I have experienced in the last at least 26 years of
driving on vehicles my family has owned was a set of cheap "T" rated
Tiger Paw Touring that got noisy and developed a vibration on our
Taurus. The tires were on the car when we bought it so no history -
and I know there was at least a few times the tire pressure dropped
below spec. They did not come apart, or even fail to the point it was
visibly detectable, but it sounded like bad wheel bearings. Bearings
didn't solve the problem - new tires did.