Do inner duals fail more often? If so, why?

RV Tire Safety
with RV tire expert Roger Marble

I recently read this on an RV Forum thread:

“Isn’t it weird how it always seems to be the inner tire that goes bad or blows? Seemed to always be my experience (bad luck) when I was driving semi’s for a living.”

While I have never seen a documented study, I can certainly believe this observation can be made by many. There is science behind the “why” this may be true.

For those that have reviewed the post on Tire Covers that explains the effect of temperature on tires, you have learned that it is the higher temperature that accelerates the tire “aging” process. If you look at the temperature readings on sets of dual tires you will see that when the tires are inflated to equivalent pressures, the temperature of the inner dual on motorhomes will usually show as a bit hotter. The difference isn’t a lot but the effects of that difference I believe are cumulative.

It is also true that older tires are more likely to fail due to the degradation of the rubber flexibility and strength.

Please do not take this observation and assume you need to start adjusting the inflation in your duals to run more air in the inner tire. Doing this could end up resulting in a shift in loading between the pair of tires to place more load on the inner tire, and we know that increased load results in increased operating temperature.

Tire operating temperature develops from complex actions of flexing of the belts and of the lower sidewall, which are the two hottest locations on a tire. You might be able to lower the temperature in one location while increasing the temperature in a different part of the tire.

The best practice I can suggest is that you:

1. Confirm the tires in each pair of duals are a “matched set.” (See this post.)

2. Ensure you know the actual load on each set of duals, not just the total axle load.

3. Use the Load and Inflation tables to learn the MINIMUM Cold Inflation Pressure (CIP) for the heavier loaded axle end.

4. Add a 10% inflation to that minimum number to establish your CIP.

5. Inflate all tires on the axle to the same CIP. (Matching the inflation within +/- a couple psi is good enough.)

6. Run a TPMS to monitor your pressure whenever driving.

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

##RVT858

 

 

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6 Thoughts to “Do inner duals fail more often? If so, why?”

  1. Farmer gene

    Rear tires usually catch things the front tires set in motion . A bolt is the most resent at the same time a front was De capping or tread separation from the carcass , I drove until one failed and used the spare on the way to the nearest repair shop . A 6 inch punch was flicked by the front and caught by the rear . Various other nails and screws have been in my experience usually in the rear . Now when it comes to rear duals on an old farm truck that does not see many miles and usually just fails because of rot , we always put the new one on the inside , that way the older outer one could be watched and repaired a little easier .

  2. Billy Bob Thorton

    The inner tires on a duel setup DO NOT fail more often. The reason you think that is very simple. When it does happen to be the case you remember the incident more, it “imprints” on you more do to the difficulty. It is that simple.

    Do this; when something goes right, don’t take it for granted, remember it, and then you will be in balance.

  3. Judy Wiemer

    Roger, what do you think of Tire Monitoring Systems?. We have a Class A Holiday Rambler Vacationer and hearing all sorts of comments good and indifferent.

    1. Roger marble

      Judy I am a strong supporter of TPMS in RV use. If you check out my Blog http://www.RVTireSafety.net you can find numerous mentions of the advantages along with my suggested guideline on how to set the low pressure warning level. Since March I have been conducting a comparison of TireTraker brand external sensors vs TST internal sensors. I have posted the actual test data that shows the pressure readings being essentially identical between the two different systems. While the TST internal system provides more representative temperature reports I have specifically addressed that in a post on the questionable value of temperature readings for any TPMS. I am in the process of writing up my final report but basically:
      TST vs TireTraker are equivalent for pressure reporting
      TST color monitor looks nicer but is harder to read if you are wearing sunglasses while you drive.
      The initial cost of the Traker is $389 while the TST is $599 but there is also the intial cost of installing the TST internal system which will be $100 to $120 for the system. The external TireTraker sensors simply screw onto the end of your metal valve stems and you can easily program the system in 15 min or less.
      Note both of the above prices include the signal booster which many RV and most trailer applications will probably need.

  4. Linda

    Not a related comment on tires BUT..where in this RV stratosphere are the Truck Camper manufactures in upcoming big party at Hershey..It seems only Lance will be there according to the list on this site..It’s sad enough that an overwhelming number of campgrounds won’t accept Truck Campers as we are an embarrassment to the monster other RVs as like we are trash folks when indeed I have well over $100,000 in my truck & truck camper and it’s is a show piece as when we drive by leaving or entering ..people look amazed and especially when parked where we can park with awnings & slides out ..like at the Coquina public beach in Bradenton,Fl. where we are welcome to park until midnight [massive area to park on nice eye level beach front] and people want to look in and see something beautiful and all the comforts of home. Maybe the Truck Camper manufactures are shunned at Hershey..So sad to have such segregation among the traveling community. I guess we T-C are all suppose to hide in the boonies somewhere. We are probably the safest RV’ers on the highways as most of us tow “NOTHING”and have complete control versus all other RV’s towing something..

  5. rvgrandma

    Our experience with the inside tire going flat was a result of the extended valve stem being punctured or broke loose.

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