News Article about Tire Age Limits

Tireman9 wrote:

k9-keno wrote:
Ok so if I had a brand new tire with sticker on it that never saw day light because it was in the cargo hold on rim in RV but the tire was 12years old would you use it???? Just curious what people would say...

I might keep it as a spare >> B U T << I would do a complete internal and external examination looking for areas of harder rubber (evidence of exposure to excess heat) and with 40 years of experience in tire examination and forensics I might be qualified to do this but I doubt that there are more than a few dozen engineers in America with comparable experience qualified to make such an examination, and the guy "bustin tires" at "Billy-Jo-Bob's Cheap tire Emporium and Bate Shop" is probably not qualified.

Simply being a cargo hold does not mean the tire was not near a heat source.

If you want to learn more you can Google my user ID name.

Well I went ahead and got a new tire the 166.00 was not worth the risk of life and limb. I will take that tire off the front and use it as a spare. Thanks for all the input

pnichols wrote:
Well ..... most/all of the tire experts'/engineers' explanations above do not seem to account for cases such as that of our current (GMC) pickup:.....

Well, let's see if we can.

pnichols wrote:
......

The former set of Cooper tires on it were AT LEAST 12 YEARS OLD before I replaced them recently ... due only to not much tread depth left. Their sidewalls showed no cracking whatsoever and the truck set most of it's life out in the California sun. This situation closely duplicated that of an old Ford pickup we had for years before the GMC.

However, of course both pickups were rarely loaded with any weight to speak of in their beds. So .... I'm very close to coming to the conclusion that it's WEIGHT ON THE TIRES WHEN THEY'RE ROLLING that's the most damaging to their internal structure - especially the sidewalls. It's weight that distorts the sidewalls (bulging them). Think of doing this distortion hundreds (thousands?) of times per minute when going down the highway. This ultra-high flexing and the heat that it creates has got to be hard on the mechanical and chemical structures of any tire. Of course this amount of flexing and heating is way reduced in a lightly loaded pickup - hence, IMHO, the reason for RV tire sidewall cracking is ultimately due to the weight that they're carrying when in motion.

There is no question that load on a tire increases the operating temperature of the tire. A fully loaded (but not excessively loaded) tire will operate at temperatures that age the rubber up to 4 times faster than a lightly loaded one.

Second, is that some tire manufacturers use sidewall rubbers that don't show cracking very readily. Unfortunately, those types of rubber are unsuitable for use INSIDE a tire. So even a heavy used tire might not show sidewall cracking and still be on the verge of failing inside.

And lastly, the types of failures we are discussing here are fairly rare. Even the infamous Firestone ATX has been described as having a failure rate of a fraction of a percent. That means that many, many people will have no problems with their tires - but that doesn't mean their particular experience (or in this case, non-experience) proves that the explanations are incorrect. It means that we are looking at things under a microscope and discerning very small differences.

So you are right, load on a tire ages a tire faster. That's one of the things that Tireman9 was trying to point out - that there are other things involved in tire aging, not just ambient temperature.

j-d wrote:
....But I have a question about Tire Age. Limited Service Spares, so common in cars, minivans and so on. They may not leave the trunk for a decade. I can imagine they're formulated for Shelf Life not Tread Wear, but is that true? If I keep one inflated, can I count on it after a dozen years or so?

2 thoughts:

1) No, I don't think any special consideration is made for temporary spares. They are made out of essentially the same materials that regular tires are made out of.

2) Temporary spares are supposed to be used for at most 50 miles (at 50 mph max!). That's a whole lot different than 50,000 miles (with occasional bursts to 75 mph!). From an engineering perspective, that difference is HUGE - and means that even an older spare will likely survive that small bit of use - just as it was intended to do.

I've only been RVing about 15 years, but I also repaired buses for our church for about that many years. It seems to me that regular driving that warms the tires up and gives them a workout helps prolong their lives. From reading here, it also seems that tires really harbor grievances. Drive over a curb, run over that big piece of junk in the road, that tire's gonna get even with a separation or blowout. Maybe not right away...

But I have a question about Tire Age. Limited Service Spares, so common in cars, minivans and so on. They may not leave the trunk for a decade. I can imagine they're formulated for Shelf Life not Tread Wear, but is that true? If I keep one inflated, can I count on it after a dozen years or so?

What pnichols said.

48 years driving RV's.

Well ..... most/all of the tire experts'/engineers' explanations above do not seem to account for cases such as that of our current (GMC) pickup:

The former set of Cooper tires on it were AT LEAST 12 YEARS OLD before I replaced them recently ... due only to not much tread depth left. Their sidewalls showed no cracking whatsoever and the truck set most of it's life out in the California sun. This situation closely duplicated that of an old Ford pickup we had for years before the GMC.

However, of course both pickups were rarely loaded with any weight to speak of in their beds. So .... I'm very close to coming to the conclusion that it's WEIGHT ON THE TIRES WHEN THEY'RE ROLLING that's the most damaging to their internal structure - especially the sidewalls. It's weight that distorts the sidewalls (bulging them). Think of doing this distortion hundreds (thousands?) of times per minute when going down the highway. This ultra-high flexing and the heat that it creates has got to be hard on the mechanical and chemical structures of any tire. Of course this amount of flexing and heating is way reduced in a lightly loaded pickup - hence, IMHO, the reason for RV tire sidewall cracking is ultimately due to the weight that they're carrying when in motion.

So everybody you got 80+ years of tire engineering experience from Engineers that worked for the two largest tire companies in the world.

Hope you find our comments informative and maybe a bit more accurate than what your brother-in-law told you after a couple of beers while sitting round the campfire or possibly what the "talking head" on TV read you from their script or possibly what the trial lawyer would try and scare you with.

burlmart wrote:
Does anybody know whether it is simply exposure to elements that causes RV tires to sidewall cracking, or is it more that they are not 'flexed' by everyday use?

The main reason for asking is I seem to recall someone telling me it was all about squishing all the oil in the rubber through all the pores by daily usage that kept tires happy longer than the rare use case of RVs. If not, I need to learn what explanation to give in the future.

Tire "aging" is complex as it is not just the time on the clock. Rubber is an Organic Compound and as such the chemical reaction (aging) never stops but it can be slowed down with cooler temperatures or sped up with hotter temperatures. If we were talking about steel and could provide protection that prevented rusting, the strength of steel does not change with time. This is why steel frame structures are good for hundreds of years.

The temperature of the rubber is one of the main, but not the only driver of the rate of the chemical reaction.

Basically the rate doubles with every increase of temp of 18°F. While the rate is not zero when the temperature is below 32°F we could use that point as the rate of 1 with 50° being 2 and 68 being 4, 86 = 8, 104 being 16 times etc and 176° being 256 times faster aging than when the tire is at 32°F. Please don't try and do the math to justify using tires longer that the tire company guidelines as temperature is not 100% of the driver of aging. I did the math just to show you the importance of keeping tires properly inflated which means they run cooler. Also the advantage of using white covers to help keep them cooler when in Sunshine.

Now the other things that affect rubber age are Ozone & UV but these only affect the surface as UV does not penetrate the rubber of a tire more than a few thousandths of an inch and same for Ozone. Heat on the other hand affects the internal components and structural strength.

The chemicals, various "waxes and oils" do need to be on the surface to provide protection. These chemicals provide protection by being "consumed" through chemical reaction. Driving (flexing ) the tire helps these chemicals migrate to the surface.

The sidewall cracking is caused by a combination of UV, Ozone and heat so minimizing the exposure to all three will extend a tire's life. Scrubbing the tire sidewall with an SOS pad not only removes the protectant chemicals it also removes the thin layer of oxidized rubber and makes scratches in the surface and provides more area for UV & Ozone to attack. This is why you should be gentle when washing tires. I suggest that you use the same soap and cloth you would use to wash a painted surface of your car or coach.

All the above is a simplification of a complex topic but I didn't think you wanted a College level lecture on Organic Chemistry.

Thank you, sir! It is a pleasure to get the facts from someone who actually knows 'em and is willing to share.

CapriRacer wrote:

burlmart wrote:
Tireman, w/ 40 years experience as tire Design & Quality engineer with focus on failed tire forensics, what is main explanation RV tires crack on sidewalls long before on a daily use, low-mileage vehicle?

Well I also have 40+ years as a tire design and quality engineer with a focus on tire forensics - just at a different company - so I feel qualified to answer your question.

Cracking is the combination of the state of the material AND the amount of flexing that has taken place.

Tires have antioxidants (AO's) mixed into the rubber and flexing the tire allows those AO's to migrate to where they are needed. Ergo, tires that are used regularly have protection that gets used up slower than the migration - and RV's are the opposite of that.

burlmart wrote:
Does anybody know whether it is simply exposure to elements that causes RV tires to sidewall crack, or is it more that they are not 'flexed' by everyday use?.....

Hopefully the above explained that.

burlmart wrote:
Tireman, w/ 40 years experience as tire Design & Quality engineer with focus on failed tire forensics, what is main explanation RV tires crack on sidewalls long before on a daily use, low-mileage vehicle?

Well I also have 40+ years as a tire design and quality engineer with a focus on tire forensics - just at a different company - so I feel qualified to answer your question.

Cracking is the combination of the state of the material AND the amount of flexing that has taken place.

Tires have antioxidants (AO's) mixed into the rubber and flexing the tire allows those AO's to migrate to where they are needed. Ergo, tires that are used regularly have protection that gets used up slower than the migration - and RV's are the opposite of that.

burlmart wrote:
Does anybody know whether it is simply exposure to elements that causes RV tires to sidewall crack, or is it more that they are not 'flexed' by everyday use?.....

Hopefully the above explained that.

If there is no explanation for a rule, is it valid?