Tire max load, max inflation and cold inflation confusion continues

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RV Tire Safety

with RV tire expert Roger Marble

The following is from an RV forum:

“My understanding is that the number on the side of the tire is not a recommendation. Rather it is the maximum cold temperature that the tire is rated for. You should never run above that number. Without actual weights, I would run the recommendation from the motorhome manufacturer on the placard near the driver’s seat, or a little higher, but never over the sidewall number.”

The information on the tire sidewall is a statement of the maximum load capacity and the cold inflation required to provide that load capacity.


Different tires have the word “max” placed in different parts of the phrase, which leads to the confusion.

Here is a post on passenger tires.

Here is a post on when the minimum inflation is the maximum.

NOTE: A statement of Max load “at” stated inflation, such as “Max load 3,000 lbs at 80 psi,” is leaving off the implied “minimum” before the 80 psi.

Also introducing the word “cold” seems to confuse some.

Maybe these will help:

• Tire inflation should only be set when the tire is at ambient temperature and has not been warmed by being in sunlight or driven on for the prior two hours.

• A tire may be loaded to the number of pounds stated on the sidewall only when the tire has been inflated, when cold, to the stated pressure on the tire sidewall.

The problem is that these phrases don’t fit in the same place as current “Max load 3,000 lbs at cold inflation 80 psi.”

 

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

##RVT907

 

 

3 COMMENTS

  1. Hi Roger. I am trying to find out the max pressure and temperature that my Michelin LT225/75R16 E tires will be before tire failure. I contacted the company and the CSR guy I spoke didn’t have that info. He said keep them at manufacture PSI of 80 and I shouldn’t have a problem with over pressure or over temperature. I want to set my TPMS over pressure and over temp values to warn me before they reach the top end and fail.

    • I have a post on my blog specifically on how I program my TPMS. http://www.rvtiresafety.net/2017/08/how-i-program-my-tpms.html
      But basically:
      1. Leave the High Temperature at the factory setting which is normally 159°F
      2. Set the LOW pressure warning at the MINIMUM inflation needed to support the measured load on your tires (scale reading and Load Infl table number)
      3. My normal cold SET pressure on my motorhome is the MINIMUM inflation number + 10%
      4. You are not going to fail your tire from normal pressure increase due to operation. We tire engineers consider that and test for it. BUT You can set a high pressure warning to your cold set pressure +20 to 25%. If you are seeing more than +25% then I suggest you do some investigating. Are all tires increasing that much or only one. If all tires then you may be using an incorrect “SET” pressure or the tire was inflated with very wet air and you may even have a puddle inside your tire.

      Check out the blog for over 300 posts on tires, valves, wheels & TPMS

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