RV Tire Safety: Tire warranty – How do engineers “read” tire conditions?

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with RV tire expert Roger Marble

I read the following on an RV forum:
Carlisle Tire’s warranty used to state ‘tires must be inflated to sidewall stated pressure or warranty is void.’ I don’t know about now though. How in the world do they determine if the tires are inflated to sidewall pressure? Is there a little gremlin with a report card in each tire? Some manufacturers just never get out of the box. Unless it was a bad tire, had been run flat previously, and most likely a bunch of other possibilities. At the time of a blow out there is no way they would know other than by assumption. Yes, most probably operator error, but only assumptions.

Sorry, but there are ways to identify the probable inflation and load history of a tire. Just as a Medical Examiner can do an autopsy and identify the signs of bad diet and poor or no exercise, or years of smoking, it is many times possible to see the physical signs of low inflation and high load.

These signs can show up in the indentation into the tire left by the wheel.

 

Here are examples of improper inflation or a Run Low Flex Failure of a P-type, ST- or LT-type tire.

Melted body cord is physical proof of extreme run low.

Also, the different flex markings can be seen on the interior of a tire. In extreme cases the inner-liner (special rubber that holds air in much like a tube did in tube-type tires) manufacturing “defects” will usually result in early life failure, i.e. <1,000 miles. Tire failure is in itself not proof of some nebulous “defect” even though lawyers and those not experienced in failed tire inspection want to think so.

Once you examine in detail a few thousand tires from both controlled testing and from day-to-day use and abuse, the conditions seen in tires tell a story of the tire’s history.

Too often people simply think of the conditions (load, speed, inflation, road) at the moment the tire fails as the “facts” to be considered when trying to decide “why” a tire failed. In reality, the damage might have been done hours, days or even months earlier.

See THIS post on a study of pot hole damage and how long it took for some tires to fail from the impact.

As I point out in my “RV Tire Knowledge” Seminars at RV conventions, tires are like potato salad: Putting the salad back in the refrigerator after it was left for hours in the hot sun does not “fix it” and make it good to eat the next day, any more than taking the burnt hot dog off the grill and letting it cool down before serving it makes for a good meal.

Adding the correct air in a tire after running it low for thousands of miles does not repair the damage. Slowing down to 50 mph after hours of speeds of 70 to 80+ over the preceding weeks and months does not “fix” or heal the thousands of microscopic cracks that were formed in the overheated and overstressed belt rubber. Once a crack is initiated it does nothing but grow. If a person stopped his smoking addiction of 2 packs a day for 40 years a couple of months ago, will his lungs be clean and clear today? Not a chance.

When examining a tire, I look at the physical condition of a tire and specifically what evidence there might be. Years of experience have taught me what to look for and allow me, as a court-certified “Expert,” to form an opinion that is based on the examination of many thousand tires.

 

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

 ##RVT933

 

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Bret

Listen to Tom below and weigh your RV, trailer or whatever to get weights on each wheel when fully loaded for travel then use the tire pressure Vs weight chart appropriate for your tires to calculate the appropriate COLD pressure using the heaviest loaded tire on each axle. Most folks add five lbs as a safety margin. Simply using the max sidewall pressure can be as dangerous as too low a pressure. that number is a maximum number the tire is rated for, and usually not what you need for your specific application. In some cases that number may exceed the maximum pressure rating for your wheels and be a possible explosion hazard. It may be a bit inconvenient, but do it right.

Jeff, you are completely wrong unless you actually have 4,800 lbs on each of those tires.

Bret

Bull

Years ago I had 6 new Carlisle 15 inch tires on the my Imperial 2 car trailer. First trip with the new tires from TN to TX had 4 of the 6 tires blow. Only 1 car on the trailer during the trip.

Carlisle inspected the tires, paid me back for the four tires I purchased on the road, paid me back for all 6 Carlisle tires I had purchased and replaced all 6 tires at no cost to me.

When I received the 6 new tires from Carlisle I sold all six tires as I had already replaced all 6 trailer rated tires with LT truck tires. I have never had another tire issue with that trailer running LT truck tires.

To this day I have only used LT rated tires on all my trailers with never tire issue since.

TRAILER RATED TIRES SUCK!

tom

You need to weigh your RV at each wheel and axle pair, then consult the tire pressure vs weight chart to determine your actual needed air pressure.
Used to own a Class A, and one of the “experts” used to swear by the sidewall air pressure, which is a “limit” indication of 80 psi. Weight charts indicated actual recommended pressure was 55 psi for the front and 60 psi for the rear. Charts from Mitchelin, I think they know their business.
Over inflated tires result in a smaller contact patch on the road and a stiffer ride. Heat build-up is also a consideration.

Jeff

I have been running my SAILUN Tires on my 5th wheel, 215 / 75R 17.5.

The cold tire pressure for these tires is 125 psi. And that is what I run them at.

I actually had a PERSON on RV Travel (explitive deleted) tell me that I was running too much pressure in these tires! And so it goes!

125 PSI is stamped on the sidewall of these tires. And that 125 PSI gives me a Load capacity of 4800 lbs per tire!

I wish RVers would learn more about tires and learn how to maintain them properly. After all your LIFE is riding on them!