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Old 05-02-2019, 05:00 PM   #1
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Why do tires fail?

Tires fail from two basic causes.

Low air pressure
and/or
Long term degradation of the rubber usually from excess heat.

Low pressure (active leak from puncture or loose valve stem or valve core are the most common reasons) can lead to a Sidewall Flex failure or more commonly called a "Blowout". The sidewall cord can melt (polyester) or fatigue (steel). Many TT owners fail to realize that they will never "feel" the results of a tire losing air till it is too late and they are surprised when the sidewall lets go. The rapid air loss "bang" even when the tire only has about 10 to 20 psi in it, is a big surprise IF they even hear it. [moderator edit] A TPMS can provide warning of air loss so is good insurance and can easily pay for itself.

The long term degradation of the rubber at the edges of the belts can lead to a belt and/or tread separation. Even if the tire keeps its air you can have this type of failure so a TPMS will not provide a warning. This degradation comes with age as the rubber is always losing flexibility. Just think of those rubber bands you found in the back of the desk drawer. Even in cool and dark they got brittle. HOWEVER, running at or near or above the load capacity of a tire will result in increased heat generation. Increased heat actually can accelerate the aging process with a doubling of the rate each increase on 18F. Running a margin of at least 15% between capacity and measured load is a good first step. Running at higher speed will also generate excess heat.

Realizing that over half of the RVs on the road have one or more tire in overload is one main contributor to the high tire failure rate. Simply thinking that a tire will fail because the tire plant building is painted blue rather than green is not logical.

Buying the lowest cost "no-name" tires is IMO a major contributor to poor results. If the main objective is the lowest cost tire why would anyone be surprised with short tire life?
Just paying more however is no guarantee of better quality. I believe the best tool available is comparing Warranty and service support.

Can you get a multi-year warranty on the tires? Is it possible to get Road Hazard coverage? Is there a nationwide network of dealers who stock the brand you are considering?


Blowout is just a catch-all to describe a failure where the person has no formal training in Failed Tire inspection or analyst.
Here are a couple of examples of Sidewall Flex failure due to running low inflation pressure.




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Old 05-02-2019, 10:23 PM   #2
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Nice write up Roger, Thanks for sharing.
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Old 05-03-2019, 12:48 PM   #3
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Great stuff, glad to see you are here!
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Old 05-05-2019, 11:59 AM   #4
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Thank you for this important safety post
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Old 05-07-2019, 05:15 PM   #5
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Another issue being two axles close together big time scrubs the trailing tire big time on hard turns.
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Old 05-17-2019, 04:56 AM   #6
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What's your opinion on proper tire inflation pressure? I thought I had always read to inflate to the maximum pressure on the sidewall. My original 2001 Sunline 2470 tires said 35PSI, and so does the label on the trailer. I got new tires a couple years back that can go to 50PSI. In reading on line, I see mixed opinions if I should use 35 (trailer label) or 50 (tire wall)?? Yesterday, I set them at 42!

What are your opinions? Thanks!
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Old 05-17-2019, 07:48 AM   #7
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Quote:
Originally Posted by Tkch88 View Post
What's your opinion on proper tire inflation pressure? I thought I had always read to inflate to the maximum pressure on the sidewall. My original 2001 Sunline 2470 tires said 35PSI, and so does the label on the trailer. I got new tires a couple years back that can go to 50PSI. In reading on line, I see mixed opinions if I should use 35 (trailer label) or 50 (tire wall)?? Yesterday, I set them at 42!

What are your opinions? Thanks!

As I have covered in detail in my RV Tire Safety blog there are a number of details needed to make an informed decision on what inflation pressure to run on your TT.


Since there will be a number of readers I will give a brief summary here.



Single axle trailers are NOT the same as multi axle units.


You need to know the actual load on the tires with the TT loaded to its heaviest. You also need to confirm you are not exceeding the information on the Vehicle Certification Label AKA Tire Placard. That label has Grose Axle rating and Grose vehicle weight rating. You should never exceed those numbers.


-Knowing the actual axle load and with smaller trailers ( No slide-out and no heavy equipment like permanent generators or water tanks larger than 30 gal with propane tank(s) mounted on the front of the RV) you can use the inflation number on the Placard as your 'COLD" inflation number. Cold means not having been driven on or in direct Sunlight for the previous two to 3 hours. OR if your



- Single axle TT can simply figure 50% of the axle load is on each tire to confirm tires are not overloaded. Hopefully, that 50% figure is no greater than 90% of the load number in pounds molded on the tire sidewall. If you exceed 90% you must remove some of your "stuff" from the RY or you can expect an increased probability of having a tire failure before 5 years use.


- Multi-axle trailer owners should know that very few trailers have the load evenly split 50/50 between the axles and very few have the axle load split 50/50 side to side, so we need a better Reserve Load. In this case, the tire load should be no greater than 85% of the tire rating in pounds.


- If you don't know the individual tire loads you should calculate the axle load split to be 53/47% and the side to side split also 53/47%. Yes, I know it is harder to find a scale where you can get the individual tire loads measured but you can find gravel pits or building supply companies that have the side clearance to allow you to learn the numbers so you can use THIS chart to learn the individual tire loads.


Tkch88 You didn't say if your tires were "P" type or "LT" type so without knowing the actual tire type it is difficult to answer that part of your question. How about posting your actual tire size (include the letters and numbers) and posting a picture of the Placard or telling us the numbers for axle load and tire inflation and full tire size shown on the sticker.
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