The Great Tire Age Debate

[Krash]

I am really not trying to start an argument, but I would like to throw out a question, and get some feedback.

I currently have Goodyear G670’s on my 2002 Diplomat. They have a date code of 0709, so the tires are about 7 ½ years old. I can’t say the actual mileage on the tires, as they were on the coach when I bought it 1 ½ years ago, but the coach has 44k on it now. The tires look fine with no cracking and normal, even wear. When I bought the coach, the owner had it parked next to his house and garage with almost no chance the sun would ever hit the tires. Of course, I have no idea of the time it was parked there, or how often it was driven, so I have very little history on the tires. I have installed a TPMS, so I monitor my pressures constantly.

My post is not about if I should replace the tires, and I know there are many opinions on the subject. My question is what about the science of it? I have read many posts where this or that tire is junk because it blew out one or two years after I bought it. I have also read this or that tire is great because I have driven on it for 10 years, and have 120,000 miles on it. I have also seen those who get new tires every 5, 7, or even 10 years. I have also read that spare tire should be replaced after the same period of time, or sooner, than the tires that have been on the road because they haven’t been exercised.

Does anyone know of any definitive testing of a tire that will tell its age/condition? Yep, I know the date code will tell me that, but I mean something with a little more meat.

For example: I have a spare in the basement of my coach that has the exact same date code as the tires that are mounted, 0709. My spare has never been on the ground. It still has the nubs on it, and even the chalk mark with the name of the customer on the tread. It seems to have never seen the light of day. Does anyone believe that if I took a core sample of that tire, and core samples of a few brand new tires of the exact same make, some laboratory would be able to correctly identify them by age?

I mean I recognize that there must be a difference between a tire that has been sitting in the Arizona sun for 5 years versus the same tire that has been parked in a garage, and driven 200 miles every month since new. I am just wondering if there is a test that shows this deterioration over time?

Shouldn’t there be some scientific way to determine if a tire is 30%, 50%, or 90% used based on age or chemical makeup? They have that test for engine oil, why not tires?

I would donate my spare, to get a definitive answer to this question. (Don’t tell me my tires are too old and need to be replaced! I am already on it, hence the donation of my spare.)

[JohnRR]

It is what it is, I've got over a 50 year back round in the automotive field and have never heard of a scientific test for tires aging out other than information from manufacturers saying to do so.

[Krash]

Well, that's my point. Precisely because we all have different rigs, environments, driving habits, etc., what makes us so sure our tires need replacing, and when?

I found this on the Goodyear site about RV tires.

"Tire Replacement Guidelines
Goodyear does not state a specific replacement age for RV tires because there are many conditions that dictate a tire's life span. Some factors that influence how long a tire will last are:

Usage per year - more frequent usage will result in longer life

Vehicle storage practices (6 months loaded with little or no rotation is not good!)

Usage in warmer climates can also impact a tire's overall life due to greater extreme ozone exposure"

They give no indication here that states age?
Tire Replacement Guidelines - Goodyear RV

[Tireman9]

Yes there are laboratory tests that can give relative age of tires i.e.
A appears to be older then B
This is based on polymer chemistry. I suggest you take a few classes in Organic Chemistry and then study up on the papers and information you find when you Google
rubber crosslink density

I think what you are missing is an understanding of the fact that the physical properties of rubber in tires changes with time and temperature. As I have covered in my blog posts on the use of tire covers I provide a simplified explination of the different rates that rubber can change or "age" depending on the temperature the rubber is exposed to.

In general all different compounds age and the ageing rate increases with an increase in temperature. The complicating issue is that different compounds are going to age at different rates and different compounds have different "strength and elastic" properties when "new" so it's very difficult to identify which compound will "fail" first because different parts of a tire have different compounds and also place different stress on the various rubber compounds.

Remember you would have to "sacrifice" a tire to dissection to learn the numbers so when done you would no longer have a tire you could run.

[JohnRR]

I ran my rears until less than a month ago replaced them at 10 years old with Michelin much to the contrary opinions here, I drove my steers home to replace here because I wanted one for a spare and did not want to try and transport it home loose.

There are so many differing opinions out there to pick from.

[Tireman9]

Yes everyone wants an exact answer i.e. 519 weeks, 4 days 8 hours and 10 minutes and the tire will fail.

Just not gonna happen.

Maybe you could answer how old can a jug of milk be before it tastes bad and how old before it will make you sick?

We are talking "organic" materials. Both milk & rubber are organics and suffer from similar effects of time and temperature vs their state after x hours at y temperature.

[Krash]

Thanks for the inputs.

It seems from the responses that I have left the impression that I want to run my tires longer. That is not the case. I am in the process of selecting new tires now. But I guess I better throw away the spare because it is just as old as the tires in service, even though it has never met pavement. I thought a better, and more practical, solution was to see if the spare could be tested to show how badly it had deteriorated from age. Might help other to determine whether to keep, or not keep a spare?

Tireman9
Could you recommend one of these labs to me? I have no knowledge of polymer chemistry or Organic Chemistry, but I did read Goodyear’s recommendation on RV tire replacement, and they make no mention of age? So are you saying my spare tire should not be used in service because it is too old?

JohnRR
That is a long time. Were they showing signs of age? Cracking, low tread depth? Just curious.

I do understand that all things age, and that age usually can be measured. Heck, even petrified wood can be carbon dated. But I am wondering what age, or condition, can determine when a tires useful life has been exhausted. That Goodyear explanation makes the most sense to me logically. And if time is a major factor, how do we determine what the time is. I don’t mean years, I mean condition. I have read about tires that had cracks in the sidewall after one year. I don’t think anyone would say those tires are good for another 5 years in that condition. Isn’t it conversely true that a tire in good, never used condition, may still have a useful life? Or is it dead based solely on age?

By the way, a jug of milk taste bad after 4 hrs, 31 mins, at 70 degrees. I am just looking for someone to taste it and confirm.

[JohnRR]

A very long time, both outside tires had weather checking on the out side walls, I inspected both side walls with a magnifying glass looking for signs of the cracks showing thread casing which they never did, then one day the inner dual showed signs of weather checking and it looked like some of the rubber was flaking between the duals. I did not check them further it was time to replace them all.

I would not encourage anyone to follow my lead with the time frame, I do not exceed 65 MPH and generally drive no more than 200 miles a day if that with a break or two along the way.

I repeatily checked the TPMS for temps and pressures I also feel more comfortable with new ones less nerve wracking being concerned about tires.

The bus was always garaged when not used and the tires covered when parked more than 24 hours outside.

Why did I not change them sooner? Just stubborn I guess.

[alpha99]

Originally Posted by JohnRR

I ran my rears until less than a month ago replaced them at 10 years old with Michelin much to the contrary opinions here, I drove my steers home to replace here because I wanted one for a spare and did not want to try and transport it home loose.



There are so many differing opinions out there to pick from.

Wow.

[Krash]

Thanks JohnRR

Although my tires are not showing any of the same symptoms as yours were, I figured based on most opinions, I better change mine now. Most would feel I am really pushing it as is. Shopping for tires now. Scary prices!

[JFXG]

Not to hijack anything here, but here's another preservation question about tires.
I've read several times that it is helpful to treat the tires with 303 to keep them "youthful". But is it only necessary to treat the tire surfaces exposed to direct daylight, even if only sometimes direct sunlight? Or must you crawl underneath and treat both sides of every tire in order to protect the tire's longevity?


John & Diane, fulltiming since '12 02 DS40, FL, Cat, '04 Element NHSO RVM103

[JohnRR]

Originally Posted by Krash

Thanks JohnRR

Although my tires are not showing any of the same symptoms as yours were, I figured based on most opinions, I better change mine now. Most would feel I am really pushing it as is. Shopping for tires now. Scary prices!

Nothing wrong with that at all. That's one of the opinions out there and you need to do what you feel is comfortable for you.

[Cloud Dancer]

Why would there be such a test? IMO there's no incentive to fund such a costly, time-comsuming, scientific test. IMO nobody, and no company, is going to assume potential liability by announcing that RV tires actually are safe past 10 years of age.
IMO none of us really know, and all we can do is decide for ourselves . What I did is my own research on what is the best choice of steps to take immediately at the first sign of a failed front steer tire. I even went as far as to learn the origin of the forces at play when this happens, and exactly why it is that I must execute the first 3 steps simultaneously. Yes, at the same time.

[jacwjames]

I'm in the same dilemma, my front tires are years old. I have taken care of the tires. I installed a TPMS and know I have not run the tires with low psi. I run the front tires at 105 psi which is higher then recommended. The tires still look like new and have 50 K on them.

I considered rotating the front tires to the rear to get a couple more years out of them. The rear tires are 5 years old.

I had checked earlier this year on replacing but decide to wait as it appear we will not be traveling in the coach for the remainder of the year.

FWIW, I ran my rear tires to 10 years. They were Goodyears and still had plenty of tread left. When I had new tires installed i inspected each of the old tires both inside and out. The looked good, no visible problems inside or out.

I have +25 years experience in the mining industry, tires were a big portion of a mines budget. The suppliers would come in 2 times a month to inventory both rolling and on hand tires. The big thing they were looking for is how the tires were being taken care of making sure the tires had proper inflation. All tires had to be within 3% size of each other. Looked for side wall cuts etc. All old tires were inspected looking for internal side wall cracking, punctures, or signs the tires were run low.