Broken Cord on Michelin Tire

[David Brady]

Thanks Neil, that helps a great deal. Glad to see you here
on this list. Just a couple of questions:

1) can I measure "deflection"?
2) does "deflection" change as the tire rotates at speed?
3) sounds like the sole purpose of tire pressure is to maintain
the correct deflection?
4) if I were able to dynamically adjust runtime tire pressures,
would optimum tire life/performance be achieved by maintaining
the correct deflection under all ambient operating conditions?

Thanks,
David Brady
'02 LXi, LV

Neil & Pat wrote:
>
> * 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
>
>
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