Broken Cord on Michelin Tire

[Neil & Pat]

Hi Pete, David, Greg, Randy and all else who have been
following this thread. You
called for a tire engineer to make input into this subject; well I have been
doing that for 36 years now and also happen to own and operate a Wanderlodge
(PT-36 ) for the past 12 years and have written extensively on the subject of
RV safety in my book on the subject as well as respond to many of the tire
questions posed on this and other forums.
Perhaps I can help.

The original question was re: a broken belt (actually shifted) on a
Michelin tire with the thought was this a problem on the Michelin tires and would
it be subject to warranty. At 27k miles the tire problem in
question is almost certainly the result of a “road hazard” either a
rock, shoulder drop off, hitting a curb or possibly even improper usage of “chocks”
for leveling or other purposes.
Had it been a manufacturing problem it would have shown up much before
that time. You did receive proper
advice in that this is not a warrantable condition by the manufacturer but
often dealers do provide “road hazard” protection as a service to their
customers.

This is one of the major differences between truck tires and those used
on automobiles; in order to carry heavy loads much higher pressures are used
and the tire is normally operated at a lower deflection rating. On trucks the deflection of the
sidewall when normally inflated is on average 8% by design when it is properly
inflated for the load carried, in contrast on an automobile tire the deflection
is approximately 12%, thus, yielding a smoother ride and a tire less
susceptible to impact loads as mentioned above. For your interest aviation tires actually operate at 32%
deflection to carry the immense loads involved but do so with a duty cycle
limited to a few seconds. The “hoop
strength” of the belt package” is under immense tension from the inflation of
the tire becoming more and more rigid and unyielding as pressure goes up making
the tire much more critical to this type of abuse. So for our RVs we have a quandary, RVs are the only vehicles
on the road, which operate at 100% of the capability 100% of the time making their
safe operation somewhat precarious.
We must carry the correct (high) amount of air pressure to carry the
load (at the correct deflection rate) but should not exceed that pressure or
operate below the required amount.
Higher pressure than required will yield decreased steering power,
braking power, higher impact type damage as well as decrease life; too low a
pressure will result in over deflection, hotter running temperatures (possibly
destructive), poor handling, greatly reduced life and the potential for catastrophic
premature failure. Take your pick,
but none of these options are very appealing to me.

The above realities of life is the reason why the tire manufacturers,
the RVSEF and myself all repeatedly attend and lecture at rallies and anywhere
RVers gather to spread the word that RVs are different and incur considerably
more operator responsibilities from the owner/operators. It is absolutely essential that you
have your RV weighed properly wheel by wheel to assure that none are overloaded
and then and only then determine the correct pressure for your specific RV
under the conditions you operate it.
Plain and simple there is no other way.

Always happy to be of assistance:

Neil LeKander

Author, The Rver’s Ultimate Survial
Guide

http://www.rvsafetyinfo.com

less likely to crush to the wheel rim,
possibly protecting the tire

from pinching damage, but the high pressure would also place the tire

under tension pressure ... so???



Any tire engineers out there?



Pete Masterson