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Wednesday, February 21, 2024

Why do tires fail? Tire expert has the answers

 As an actual Tire Design and Quality Engineer, I know from my 50 years of tire experience, including 25 with a primary focus on failed tire forensic inspection, that tires fail from two basic causes:

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

Low air pressure

An active leak from a puncture or loose valve stem or valve core is the most common reason. Also, poor or no inflation maintenance contributes to low air pressure as all tires lose pressure at about 1% to 2% a month, excluding the pressure change due to changes in ambient temperature, and can lead to a sidewall flex failure, more commonly called a “blowout”.

The sidewall cord can melt (polyester) or fatigue (steel). Many travel trailer and fifth wheel owners fail to realize that they will never “feel” the results of a tire losing air until it is too late. Then 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. A tire pressure monitoring system (TPMS) can provide warning of air loss, so it is good insurance. A TPMS can easily pay for itself many times over.

Long-term degradation of rubber

The long-term degradation of the rubber at the edges of the belts in radial tires 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 in this case.

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 old desk drawer. Even in cool and dark they got brittle. However, running at, 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 with each increase of 18 F. Running a margin of at least 15% between tire capacity and measured load is a good first step. Running at higher speed will also generate excess heat. For ST-type tires, this means faster than 65 mph, no matter the Max speed rating.

Realizing that more than half of the RVs on the road have one or more tires 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. But many still have feelings along those lines when it comes to where a tire is made.

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 tire shopping 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? The answer to these questions may provide a better indication of tire quality than the opinion of other RV owners published on the internet.

There are some self-appointed “experts” out there who think that selling tires for a numbers of years qualifies them to make technical pronouncements on tire technology. I would suggest that people review "The Pneumatic Tire"   published by the US DOT before making a claim of being a “Tire Expert”.




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