Replace tires due to age

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Originally Posted By: Cardenio327
Originally Posted By: 440Magnum
But I have yet to hear a convincing argument of exactly HOW the structural part of an undamaged tire deteriorates simply due to age. The first few micrometers of rubber- YES: UV and ozone cause it to deteriorate. But the cords? The internal rubber packed around the cords, totally protectd from UV and isolated from chemical attack unless there are punctures? I just don't get it. I never HAVE gotten it, and I've run a couple of sets of tires (admittedly on low annual mileage vehicles like my '69) for well over 10 years. Would I take them out and run at 80 on I-10 to El Paso? Probably not- but is that just because I've caught an irrational fear? I honestly don't know.


I'll offer an explanation, lets not call it an argument:

In my training at a Firestone factory they explained it in this manner:

Tires are made up of many individual components. Many of these components are different compounds of rubber. Each compound of rubber will vulcanize at a different rate. Accelerants and retardants are added to the different rubber compounds to ensure that they all finish vulcanizing at precisely the same moment. The accelerants continue to work once the vulcanizing process stops, the final result being the degradation of certain rubber components after 6 to 10 years. Sunlight, heat, air pollution, &c. have their role as well, but the accelerants are what cause the internal components to degrade.

Tires from years ago most likely had a much longer shelf life. My Dad has a pair of new General 7.50-16LT tires sitting in an wall-less shed that still look to be in good shape. They have been sitting there for 20 years.

Manufacturers also may add accelerants to speed up the vulcanizing process. Time is money. At Firestone's Cuernavaca plant each vulcanizing machine can only vulcanize four tires at a time. There are ranks and files of these machines, each is about the size of an automobile, and must cost a fortune to purchase and operate. If I remember right Firestone vulcanizes automobile tires for 9 minutes. Each additional minute would greatly increment the cost of the tire.


I think though on a mounted tire their are effectively no air exchanges so any volatile compounds realeased from the inside of the tire quickly reach a stable vapour pressure and then no more evaporation/sublimation occurs.

Of course the outside of the tire is exposed and I think when it cracks, then the structural rubber compounds cand start degrading and maybe quickly? I have blown up a couple small trailer tires in my younger/dumber days but they all had significant surface cracking and were probably 15+ years old.
 
Storing tires(that are in use as opposed to new unused) can actually age them faster than actually using the tires daily.

Since its a sports car would definitely replace them.

Just for the performance improvement alone.
 
I had the tread fly off of a tire on the highway. The tire was old, but still in good condition. Luckily, the tread just separated and the tire didn't lose air. I was able to safely pull over.

This was years ago when I was young and less educated about vehicles. The car was purchased from an elderly person. The tires had more than 50% tread, but after that one came apart I went and bought a new set of low-priced tires.

I would recommend following the manufacturers' recommendations to replace the tires.
 
Originally Posted By: Cardenio327
Originally Posted By: 440Magnum
But I have yet to hear a convincing argument of exactly HOW the structural part of an undamaged tire deteriorates simply due to age. The first few micrometers of rubber- YES: UV and ozone cause it to deteriorate. But the cords? The internal rubber packed around the cords, totally protectd from UV and isolated from chemical attack unless there are punctures? I just don't get it. I never HAVE gotten it, and I've run a couple of sets of tires (admittedly on low annual mileage vehicles like my '69) for well over 10 years. Would I take them out and run at 80 on I-10 to El Paso? Probably not- but is that just because I've caught an irrational fear? I honestly don't know.


I'll offer an explanation, lets not call it an argument:

In my training at a Firestone factory they explained it in this manner:

Tires are made up of many individual components. Many of these components are different compounds of rubber. Each compound of rubber will vulcanize at a different rate. Accelerants and retardants are added to the different rubber compounds to ensure that they all finish vulcanizing at precisely the same moment. The accelerants continue to work once the vulcanizing process stops, the final result being the degradation of certain rubber components after 6 to 10 years. Sunlight, heat, air pollution, &c. have their role as well, but the accelerants are what cause the internal components to degrade.


That actually does make a lot of sense to me. If the damage process is due to a reaction of compounds that are effectively embedded in the rubber, then it doesn't matter if there's a path for oxygen, ozone, etc. or not.

It also seems like the tire manufacturers could tweak the process to inhibit the leftover reactants better... but I'm not a chemist.
 
Interesting...the day I post this topic our local news station runs a story on the dangers of old tires. Ford, Chrysler, and GM say to replace after 6 years and the tire manufacturers say 10 tops. So they are history...I'd rather not flip over at 80 MPH. I did that once and don't think I have 9 lives to use up.

The worst part is the sleazy tire dealer trying to peddle a 13 year old tire as in good shape. It's hard to tell if these guys are clueless, or sinister.

http://www.newsnet5.com/news/local-news/...trophic-failure
 
I have a 1999 Trans Am and drive it / store it similar to yours. I replaced its origional factory tires in 2012. They were visually in good condition but the ride quality had diminished as the rubber seemed to have hardened up. I have a 1987 Chevy plow truck which I hate to admit, has winter tires on it from a previously owned truck. The tires must be from the mid 1980's. They have inner tubes in them because I was getting constant rim leaks. They are still holding up driving around town, but I never take the truck on the highway.
 
Just noticed you are a local
smile.gif
 
My LS400 and E430 came with full size spare, the spare in LS400 used 3-4 times and the spare in E430 didn't use at all, but I replaced both at 10 years with take off tire at DT/AT.
 
Does average ambient temps matter? I'd think tires in the hot southern climes would deteriorate faster.

I say, wrap some plastic around the fenders (or oil 'em up) and lay down some rubber. Although I'd think the tires would be that much more apt to lose tread in big chunks, if tire deterioration is true. After all, heat build up due to burn-outs is gotta be well past whatever they were designed to withstand.

I'm guessing you've never done a protracted burnout; but if you have I'd probably toss, if but for peace of mind.
 
Originally Posted By: 440Magnum
Obviously the safest option is to spend money and (presumably) guarantee that you have safer tires. In fact I think there would be a liability if a tire dealer told you otherwise in today's litigious climate.

But I have yet to hear a convincing argument of exactly HOW the structural part of an undamaged tire deteriorates simply due to age. The first few micrometers of rubber- YES: UV and ozone cause it to deteriorate. But the cords? The internal rubber packed around the cords, totally protectd from UV and isolated from chemical attack unless there are punctures? I just don't get it. I never HAVE gotten it, and I've run a couple of sets of tires (admittedly on low annual mileage vehicles like my '69) for well over 10 years. Would I take them out and run at 80 on I-10 to El Paso? Probably not- but is that just because I've caught an irrational fear? I honestly don't know.


First, I am NOT a rubber chemist, but I have some experience in this area.

Second, I don't think the accelerants in rubber compounds is what causes aging - and I'll explain in a moment.

Third, did you know that gases pass through the tire? Yes, we've talked about the rate at which nitrogen and oxygen pass OUT of the air chamber through the tire, but we haven't talked much about the Law of Partial Pressure of Gases - also known as Dalton's Law. That says that you can treat a mixture of gases as though each gas is independent of the others.

So if air is 21% oxygen and the atmospheric pressure is 14.7 psi (the absolute pressure at sea level), then it is like oxygen is pressurized to 3.1 psi. If I have a tire 100% filled with nitrogen, the oxygen is trying to get into the air chamber through the tire with a pressure of 3.1 psi - and it doesn't matter what the pressure is inside the air chamber. It could be 1000 psi, and the oxygen outside is still 3.1 psi higher than the oxygen pressure inside (at least at the start.) and it will migrate through the tire into the air chamber. And, yes, they have verified this.

So contrary to popular opinion, the rubber on the inside of the tire can be attacked by oxygen.

I am not convinced that UV rays are what causes rubber deterioration. Evidence? When tires are placed in an oven (a process we call "heat aging"), they react very similarly to tires out in the open. Also, if UV rays were the major cause, then tires stored in a warehouse would be basically immune to the affects of aging. (Put another way, would you buy a 10 year old, but unused tire?)

And one last bit of evidence: If you catalog the statistics on tire failures by state, the same 5 states always rise to the top in basically the same order (AZ, CA, TX, NV, and FL). Yes, that has not been adjusted for the size of the tire population (I'm sure there is a way to do that, but I just have never seen anyone try.) - and if it were adjusted by tire population, I'm sure AZ would be off the chart.

The other thing interesting about that statistic is FL. All the other states are in the desert southwest - and I think it is obvious it gets plenty hot there - except in the winter. But interestingly, FL's weather doesn't vary as much, but it remains warm through the winter.

So I tend to think rubber deterioration is driven mostly by heat. - and a corollary to that would be that in cold weather states, the tires age more slowly.

So I tend towards a sliding scale of when to remove tires due to age. 6 years for AZ, CA, TX, NV, and FL - and 10 years for MN, MI, ND, ID, and MT - and everything else in between is ... ah .... in between.

One of the more interesting aspects of this is where do you draw the line? How bad does it have to be before the tires should be removed? Is there a way to gauge the state of the rubber?

Well ...... Cracking is sometimes used as a gauge, but it is unreliable for several reasons:

1) Sometimes the types of rubber used in the sidewall are fairly immune to the affects of aging - unlike the rubber used internally.

2) Sidewalls are also sometimes heavily loaded with antioxidants (AO's) and that artificially slows the rate of deterioration.

3) Cracking is a function of the state of the rubber AND the amount of flexing that has taken place. So even a very old, but unsed tire might not show any cracking because it hasn't been flexed - and will very quickly crack when flexed.

So, cracking can indicate a problem, but its absence doesn't indicate an absence of a problem.

Overall, we are talking about risk. The older the tire, the more likely there is to be a failure. Several very smart people have tried to analyze this, but there is so much scatter in the data, it is hard to sort it all out.

And then there is the issue of how much risk is too much? - or conversely, when is it unsafe to operate an old tire? Unfortunately, there is no clear cut breakoff point.

And since heat is a major factor, and the region the tire is operating is also a major factor, it is difficult to make a simple statement that really coveys any sort of accuracy without being overly alarmist, but at the same time adequately reducing the risk.

So to our original question. Ohio? In between state, but close to the cold weather states.

Stored vehicle? Doesn't matter.

Hardly used? That matters some, because of heat being generated during operation, but in this case I think age is more important.

And lastly, people can feel the tire start to separate if they are paying attention. At highway speeds, there will be a small vibration that will gradually get worse over the course of several hundred miles. But at highway speeds, the centrifugal forces cause the tread and top belt to come off quite dramatically.

At - say - 35 mph, you are much less likely to feel the separation as a vibration, but you might pick it up when you go around a corner. It will feel like the car lurches sideways as the tire rolls through the worst part of the separation. On the other hand, those sorts of speeds don't generate much centrifugal force, so the risk of damage is lower.

OK one more last thought: Why haven't tire manufacturers done something to extend the life of the tire? You might argue that it's a conspiracy to sell more tires.

But the truth is that they haven't found anything that works - except they have found that making improvements in durability does result in lower failure rates, but the deterioration due to age follows the previous curves - albeit at a lower rate.

What about adding more AO's? The problem here is that AO's are very expensive, and if you double the amount of AO's in the mixed rubber, by the time the tire gets heated in curing, most of the AO's don't make to the finished tire. So lots of cost with little benefit.

So that's it folks. Hope you enjoyed.
 
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CapriRacer- very good summary. I agree that any polymer is susceptible to having atmospheric gasses (including oxygen and ozone) diffuse through the tire, but its got to be extremely slow exposure rate compared to the inner and outer surfaces that are constantly exposed.

Another question I have: why have tires made in the last 10-20 years become SO much more susceptible to aging that tires made 20 - 30 years ago? I used two 1984-manufactured Goodyear Eagle tires on a beater car from 2003 to 2006. Daily driven, and yes they were horrible tires, but they worked and never failed. Back in the 70s and 80s, we never worried AT ALL about tire age, just wear. Is it due to more advanced compounds being used to make tires perform so much better nowdays?
 
CR...that was a good read. I had to replace mine at nearly 9 years old due to the flex the tire had while turning...I knew the sidewalls were going. The tire looked fine in every other aspect.

So 6-8 is what I would push here...
 
I did a huge amount of research this year on this issue. CR is 95% correct. The primary driver of aging is oxygen sublimating through the inner liner into the interior layers of the tire. This is why TIA and RMA claim, correctly IMHO, that tires do not really begin to age until they are inflated.

http://tires.about.com/od/Tire_Safety_Maintenance/a/The-Science-Of-Tire-Aging.htm

Oxygenation hardens the layers, leading to tread separation. Cracking can occur, but not necessarily, because the tires are aging from the inside out. Extreme heat accelerates the process by making oxygen more reactive, but lack of use doesn't help. Rolling on the tires distributes the internal oils that keep the layers lubricated and fresh, so storing the car actually matters very much.

This is why the biggest danger in terms of tire aging is often the spare. It doesn't get used and is stored for years in a trunk that can get very hot.

But overall I think you're in danger and the tires should be replaced.
 
Originally Posted By: 440Magnum
CapriRacer- very good summary. I agree that any polymer is susceptible to having atmospheric gases (including oxygen and ozone) diffuse through the tire, but it's got to be extremely slow exposure rate compared to the inner and outer surfaces that are constantly exposed.......


Ya' know, every time I make a long explanation, I always leave something out - and in this case it was the difference between a tire filled with 100% nitrogen and a tire filled with 100% air.

As I explained above, a 100% nitrogen filled tires is subjected to a 3.1 psi oxygen pressure from the outside.

A 100% air filled tire at 30 psi is subjected to 6.3 psi oxygen pressure from the inside. Even at 35 psi, the oxygen pressure is only 7.4 psi.

So an air filled tire is only subjected to roughly twice the oxygen pressure. It's not a great difference.


Originally Posted By: 440Magnum
.....Another question I have: why have tires made in the last 10-20 years become SO much more susceptible to aging that tires made 20 - 30 years ago? I used two 1984-manufactured Goodyear Eagle tires on a beater car from 2003 to 2006. Daily driven, and yes they were horrible tires, but they worked and never failed. Back in the 70s and 80s, we never worried AT ALL about tire age, just wear. Is it due to more advanced compounds being used to make tires perform so much better nowdays?


That's a really interesting question. I can't really answer the question, but I can give you some insight into what may be going on.

I've estimated that even the infamous Firestone ATX's only had a failure rate of 1/4% to 1/2%. That means that the odds of an individual experiencing a tire failure was pretty low.

The second thing is that prior to the Ford/Firestone controversy, the only ones who knew about tire aging were the tire manufacturers. There's a dual edged sword here. If a tire manufacturer states that tires should be removed for X reason, then they get accused of trying to frighten customers into buying more tires. If they don't, they get accused of not caring about the welfare of their customers. Prior to the Ford/Firestone controversy, tire manufacturers were more afraid of the first accusation then they were of the second. That has changed, but I can easily imagine the situation reversing itself over time back to where it was.

Also, 30 years ago, there just weren't 80,000 mile tires. More like 40,000 miles. Plus, it took a while for radial tires to be adopted. Even by 1984, there were still significant bias tire production (and I'm only talking passenger car tires here.)

Add to that that the vehicle population is about 50% higher now ...... well, you get the idea.

So I think there is now increased awareness, and there is an increased population, but I also think the incident rate has been low - even back then.
 
Originally Posted By: AboutTires
I did a huge amount of research this year on this issue. CR is 95% correct. The primary driver of aging is oxygen sublimating through the inner liner into the interior layers of the tire. This is why TIA and RMA claim, correctly IMHO, that tires do not really begin to age until they are inflated.

http://tires.about.com/od/Tire_Safety_Maintenance/a/The-Science-Of-Tire-Aging.htm

Oxygenation hardens the layers, leading to tread separation. Cracking can occur, but not necessarily, because the tires are aging from the inside out. Extreme heat accelerates the process by making oxygen more reactive, but lack of use doesn't help. Rolling on the tires distributes the internal oils that keep the layers lubricated and fresh, so storing the car actually matters very much.

This is why the biggest danger in terms of tire aging is often the spare. It doesn't get used and is stored for years in a trunk that can get very hot.

But overall I think you're in danger and the tires should be replaced.



Great info in this post and others.

I just found a great deal on tires that I've had my eye on but wanted my tires to wear a little bit more so was in two minds on what to do.

The tires have unlimited time warranty so now that I know I can store them until I'm ready to put them on, I've pulled the trigger and gotten a great deal while I can get the remaining life from what I have on.
 
Originally Posted By: TrevorS

The tires have unlimited time warranty so now that I know I can store them until I'm ready to put them on, I've pulled the trigger and gotten a great deal while I can get the remaining life from what I have on.


What tire brand has an unlimited time warranty? I've looked at the warranties from several major brands before and all the ones I've looked at have time limits on the warranty starting at the time of purchase or manufacture.

Just a couple examples:

Michelin
http://www.michelinman.com/automotive-tires/warranty.page#limited_warranty
Quote:
All Michelin tires4 (both Replacement & Original Equipment) come with a limited warranty for treadwear, as well as a limited warranty which covers defects in workmanship and materials for the life of the original usable tread, or for 6 years from date of purchase


Goodyear
http://www.goodyear.com/en-US/tires/warranty/auto-light-truck
Quote:
Additional provisions

A tire has delivered its full original tread life and the coverage of this warranty ends when the treadwear indicators become visible (worn to 2/32 in. or .16 cm), or 6 years from the date of original tire manufacture, or new tire purchase date (whichever comes first). (Without proof of purchase, the date of manufacture will be used to determine eligibility.)


Firestone
http://www.bridgestonetire.com/customer-care/tire-warranties/firestone-warranties
Quote:
coverage extends up to (a) 5 years from the date of purchase – proof of purchase date required, or (b) 6 years from the date of tire manufacture without proof of purchase date.
 
Originally Posted By: TrevorS
Pirelli


Hmmm.....

Who told you that there were no time limits on the Pirelli warranty? My interpretation of the warranty doesn't exactly agree with that.

For example, it says this about dry rotting:
http://www.pirelli.com/tire/us/en/car/find-tire/all_about_tires.html?tab=7
Quote:
What Is Not Covered By The Warranty?
Tires with weather cracking which were purchased more than four years prior to presentation for adjustment (If no proof of purchase date is available, tires manufactured four or more years prior to presentation for adjustment).


It also says you can only warranty a tire for ride-related complaints (which I assume means high road force numbers) for the first year or 2/32nds. So, you'd better get them installed and get some miles on them before they're a year old.
Quote:
If tire is presented for ride related anomalies the initial warranty period is one year from the date of original retail purchase of the vehicle or one year from the original retail purchase date of the replacement tires or within the first 2/32 nd of the original useable tread, whichever occurs first.
 
I have been a collector for many years and also hate to replace tires, BUT the rubber does go bad and does weaken the tire. If for only storing to moving the car around/showing, I would not worry about it. But if you drive like you stated, I would change them today... Pretty stupid to take the chance with your life by saving a few dollars on new tires.
 
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