Quote:
Originally Posted by Sirrotica
The bonding of the rubber to the steel belting is what does modern tires in. When the bond starts to be compromised is when the parts inside start delaminating from each other.
The Firestone debacle years ago was said to be due too the fact that the materials that the steel belting were made from, were stored outside. Rust started on the steel cords, and that made the bond of the rubber to steel was compromised from the beginning. No one can look inside of a tire after manufacturing to see if the steel to rubber bond is compromised, so there is no way that eyeballing the outside of a tire can determine if the core parts are breaking down. This is the reason that some people can run tires for 15 years without incident, and others fail internally at 5 years.
Radial tires are much more suseptible to belt failure than bias ply tires are, due to the angle the belts are in relationship of each other. The belt angle is also the reason that the old bias ply tires could have sidewall punctures repaired, and radials can't have sidewall repairs. The fact that radial belts don't criss cross in the sidewalls, makes the sidewall rip from the bead to the treads, ending the life of he tire.
That's how I understand the reasons given by manufacturers for radial tire failures, YMMV.
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Good info, thanks!
All the comments in this thread make sense to me, and I used to do the math to predict product failures. Fortunately, I never worked on stuff like tires where people could die if I was wrong.
The biggest mess with this stuff is the variation in time to failure across ALL tires a manufacturer ships is HUGE. For a tire, it would not surprise me that 1% will fall apart before 5 years and 1% would survive well past 20 yrs. Predicting the life for any single tire on any car in any climate with any driver, etc. is not going to happen as you have all discussed.
So yes, the probability for early failure may be low, but the
consequences of a failure are what matters when either you or a manufacturer makes decisions about tire life.
A manufacturer is going to protect itself and set a line in the sand that may seem WAY conservative for most of us... but we aren't the ones getting sued if someone gets injured or worse.
I think the biggest takeaway for me is that internal tire failures are not always visible. Cracking on the outside is obvious, delamination or material degradation on the inside isn't.
And some of the new tires I've bought cracked in only a few years, which is frustrating considering their cost.