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Old 01-10-2015, 01:08 PM   #21
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Quote:
Originally Posted by lbrjet View Post
What does load formula have to do with anything if max pressure is always to be used period?
2010 F250 5.4L 3.73
2011 Flagstaff 831FKBSS
Equal-i-zer 4pt 12K
Load formula and the tables they generate are of use in most applications. Multi-axle trailers are a relatively new part of the market and as the % RVs with multi axles grows the problems associated with the unique structural loading are becomming more aparent. The problem is that any effort to apply engineering principlles and say limit tandem application to "dual" tire loading is quickly met with opposition by RV assemblers who do not want to have to place larger tires or decrease load capacity on their trailers. Of course Lawyers are part of the problem for as soon as the regulations change there would be lawsuits sufficient to put every RV company out of business as they demand the RV companies replace every tire they ever sold.

Finite Element Analysis and the computer power to run the programs are relatively new. This analysis provides a logical explanation for the relatively high failure rate of tires in multi-axle application while single axle application applications of the same product do not have similar problems.
I and others have offered suggestions on how ti improve tire life and reduce, but regrettably not eliminate, the damage done to the tire belt structure.

You are of course free to ignore this and related advice. I would only ask that those that feel they know more about tire performance based on the fact they have used a couple dozen tires over their lifetime rather than engineering data and testing based on tens of thousands of tires, refrain from complaining when they suffer a tire failure.
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I write a blog on RV tire application and safety and give seminars on tires at RV events across the US. 40 years experience as tire design & quality engineer for major tire mfg. Freelander 23QB on Chevy chassis is my RV
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Old 01-10-2015, 01:27 PM   #22
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Originally Posted by ronb707 View Post
Thanks llberg for the link back to etrailer about the max pressure on ST tires. The author there needs to supply me more info/supporting data to convince me of what he said.

Regardless, you and I are covered as we have "D" rated tires inflated to their max (and the max allowed by the wheels) of 65 psi. Once again, this load range rating of 2,540 lbs per tire surpasses the axle ratings and the actual weight of the RV at each tire.

I am not faulting fellow RVer's who tow a similar rig with "E" rated tires. I believe there was no benefit to me with my known weights and the information passed on to me by both Lions Head wheels and Maxxis technical support.

To me it was a great relief to get the factory spec tires off before a blowout and at the same time upgrade to a known good reviewed "D" rated tire (ST Maxxis 8008). Moving farther up the list to an "E" rated tire would not have improved my comfort zone that much more, if at all. Time will tell if I made the right decisions.
I agree with you. The E rating would have only provided some excess capacity. It would have been a law of diminishing returns at that point. I think you make a good choice with what you did.
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Old 01-10-2015, 01:49 PM   #23
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Thank you for the link to your blog Roger. I found it to be very helpful and informative.

I think you are doing a noble task by providing this information to the public.

Cheers to you.
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Old 01-10-2015, 04:56 PM   #24
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The term "Blowout" is used as a generic term to mean the tire failed and the person using the term has no idea why.
If they mean the sidewall failed and there is physical evidence of heat i.e. melted and hard polyester, then what it should call the condition is a "Run Low Flex Failure"
If you mean the tire still held air but the belts and or tread came off then you have a tread or belt separation. This is caused by long term degradation of the rubber abound the belts or between the tread and top belt along with inter-ply shear forces exceeding the strength of the rubber to resist crack formation and crack growth.

If you can't properly describe the condition there is no hope of understanding the real cause and if you don't know the real cause there is no hope of preventing a re-occurrence.

Think of this like saying the man is dead.
Heart attack, gun shot, poison, hit by a car etc etc are all possible reasons but even then you haven't adequately described the real Root Cause.
Even if you say gun shot you don't know if it was because he was executed by firing squad, shot by police in commission of crime, shot by spouse during argument, shot while cleaning the gun, was a soldier at war etc, etc.

In my blog I have a report showing a "Blowout" but the evidence proves the tire was run flat even though the driver refused to accept the idea the tire lost air.
Sorry but simple uninformed beliefs do not trump facts in the real world.
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I write a blog on RV tire application and safety and give seminars on tires at RV events across the US. 40 years experience as tire design & quality engineer for major tire mfg. Freelander 23QB on Chevy chassis is my RV
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