Tire Failure

[Bob Schuman]

The attached photo is of the spare tire in the trunk of my 48 Olds (the same thing could even happen to a Cadillac). The tire blew out in the trunk, having never been used during my nine years of ownership. Apparently a dry rot failure, as the tire was 22 years old. Looks like the professional advice to never use tires older than ten years is correct, at least this made a believer out of me.

[Scot Minesinger]

I read 6 years is about the useful life of a tire to avoid dry rot.  I had some decent Goodyears on my daily driver a Ford 2007 CVPI that were about 6 years old and due to mileage were starting to look like replacement was a good idea.  The bigger problem was the rubber lost the ability to grip the road and dry rot had started to set in.  I replaced them, and way better traction in the rain.

This is a problem in the collector world because folks drive usually less than 2k miles per year on tires with a mileage tread wear rating that if it were not for dry rot, they would last a life time.  I usually replace my tires even on the collectors every 6-8 years.  My red 1970 DVC is coming up on needing a new set strictly due to age -ouch.

I try to buy real high quality tires, because they tend to last longer (not dry rot). 

[Eric DeVirgilis CLC# 8621]

I've noticed that radials tend to be more affected by dry rot than biases. Never was able to discover the exact reasons why.

To this day, it's not uncommon to see original spare bias tires significantly older than the tire shown here that haven't blown out while still holding air.

[TJ Hopland]

The newer the tire the shorter their lives seem to be.  Around 2000 seems to be when that started happening.  Not that it was ever a good idea to be running 20 year old tires but now days you especially don't want to do it.  I think what Scott observed with the loosing grip may be part of it.   I suspect what ever magic flavoring that makes them extra grippy when they are new maybe makes them more brittle after it wears out or breaks down. 

Interesting what Scott said about buying 'high quality' tires.   Just curious do you mean the historically big 'good' brand name tires?  Or ones with the higher mileage and warranty ratings?    I started out with the lesser brands because that was all I could afford.   For a while went to the big name high mile tires but started to think I wasn't getting any more value possibly even less.   Now my problem is I only have one car less than 20 years old and that car has slightly odd size tires so not a ton of choices there and the rest of my fleet are 75 or 70 series tires which are getting to be pretty rare so not that many choices there especially if you want some sort of white wall.   

FWIW Cooper Trendsetter has added a few more white wall sizes.  They now have a 235 75 15 and a 215 75 15 as well as the 70's that fit the 80's and earlier 90's cars.   I just got a set and I'm curious to see how they compare to the Hankook Optimos.   Sure the white wall isn't 'correct' in most cases but since they will die from dry rot I can live with that for the savings.  The Coopers and Hankooks are less than $100 vs the $200+ that the classic tires are getting to cost.         

[Jon S]

The newer the tire the shorter their lives seem to be.  Around 2000 seems to be when that started happening.  Not that it was ever a good idea to be running 20 year old tires but now days you especially don't want to do it.  I think what Scott observed with the loosing grip may be part of it.   I suspect what ever magic flavoring that makes them extra grippy when they are new maybe makes them more brittle after it wears out or breaks down. 

I'm convinced the tire manufacturers use poorer quality rubber today than they did 30 years ago. I believe this is by design. Tires lasted too long and profits began sagging. I have Goodyear tires on my Mustang that within a year have surface cracks all over them while the Michelin X tires on my 1973 Lincoln are 45 years old and still look like new without any cracks whatsoever.

Synthetic rubber should be better than natural rubber but I have my doubts.

       

[Mike Josephic CLC #3877]

Tires are a rather complex mixture of chemistry and
engineering.  I once wrote an article for the Self Starter
on the subject.  The whole picture is too detailed for
a posting here but this is a overview.

All tires are blends of natural and synthetic (petroleum
derived) rubber.  There are a number of chemical
additives in them to formulate properties such as:
traction (grip) wet and dry, heat, ozone and UV stability,
cord adhesion (especially with steel belts), handling
properties, tread life etc.  Balancing the chemical mix
and the mix of natural vs. synthetic in a given tire type
is a careful trade off to get the desired properties.  For
example, you could formulate a tire to last 100,000
miles but wind up with very poor road gripping ability.

Natural is not necessairly "better" than synthetic it's
just different.  The percentage of natural vs. synthetic
is varied depending on a number of factors:  type
of use, desired properties, cost of petroleum vs.
natural rubber among others. 

Radial tires for cars use mostly syntheric rubber due
to the properties needed whereas tires for aircraft
are mainly composed of natural rubber.  Just two
examples.

The first synthetic rubber was made in 1909 (isoprene)
by Bayer in their laboratories in Eberfeld Germany.
I worked for Bayer for 35 years in their chemicals group.

Mike

[The Tassie Devil(le)]

G'day Bob,

Definitely an eye-opener.   The only problem I have had with tyres is tread separation, and that in itself is terrible whilst driving.

Thanks for posting it.

Bruce.

[pmhowe]

In 1967, when I was in graduate school, I had a Morgan Plus 4 drophead coupe. I ate peanut butter sandwiches for a long time so I could afford Michelin X tires. The tires were great on dry ground - far better than the Avon tires the car had previously. Also, Maryland allowed them to be used in place of snow tires, an added advantage for me. The tires were great in dry weather and improved handling and ride immensely. However, on wet pavement, they had the unfortunate tendency to let go precipitously. I had a few scares, before I learned to drive warily in wet. On the flip side, in 1961, I had a 1938 LaSalle sedan with bias ply tires. The car performed flawlessly, even in snow. Of course, I drove it differently.

Phil

[Cape Cod Fleetwood]

I've noticed that radials tend to be more affected by dry rot than biases. Never was able to discover the exact reasons why.

To this day, it's not uncommon to see original spare bias tires significantly older than the tire shown here that haven't blown out while still holding air.

The Ark's original spare. Has some wear, not a lot, and holds pressure to the pound.

The ONLY tires I'll use on my drivers are Michelins. I check inflation monthly, rotate every 6K, FB then XX then FB etc. and will have them all rebalanced at the slightest sign of a shake. I've always exceeded their stated mileage life before I replaced them. Swear by Michelin. YMMV

\m/
Laurie

[Maynard Krebs]

.. But, Laurie; WHERE can YOU buy Michelin tires big enough for your big RWD Fleetwood?   I figure that they no longer exist.

You need a P235/75R-15, right... or at least a P225/75R-15.

"Fifteens" are getting hard to find.   My two '89 Caprices with the optional F41 sport suspension.. call for P225/70R-15.... and THAT is difficult.   I had to special order a set of BFG Radial T/As in order to get that size... and HUGE money!!

My '88 Lincoln Town Car calls for P215/70R-15... and I put Uniroyal Tiger Paw II (made in a Michelin plant) on it... and they're fine---nice whitewall, too!   Pricing and performance is very good----but don't make any bigger . . . . . .

[Jon S]

The Ark's original spare. Has some wear, not a lot, and holds pressure to the pound.

The ONLY tires I'll use on my drivers are Michelins. I check inflation monthly, rotate every 6K, FB then XX then FB etc. and will have them all rebalanced at the slightest sign of a shake. I've always exceeded their stated mileage life before I replaced them. Swear by Michelin. YMMV

\m/
Laurie

I'v never had to re-balance a tire in my life. Once balanced unless you lose a weight they should be fine until replacement.

[Scot Minesinger]

Jon,

What causes tires to need balancing is pot holes that slightly dent the rim, uneven tire wear, and other factors I might be missing.  Gentle drivers that drive infrequently on smooth roads may be blessed with never having to balance, but not me.  When my Crown Vic turned about 105k miles as mentioned earlier and I replaced the tires, they would not balance on the old rims because they were beat up from driving on RT 81 in VA (520 miles round trip) at 78 mph for numerous trips to visit my son in college.  Luckily steel Crown Vic rims are not expensive and so replaced bot rims and tires.  Smooth as glass now.

[z3skybolt]

Tires are weird.  I once bought a 20 year old 1982 Mercury Grand Mauquis with only 61.000 miles on it.  The original, unused spare was still in the trunk.  After driving the car many thousands of miles I mounted the (now 25 year old) spare tire...a Goodyear brand.  Drove the car,with the spare on the ground another 20,000+ miles without issue.

My 1985 Lincoln TownCar, which I bought new, has 22 year old UniRoyal tires on it with about 30,000 miles on them. I drive the Lincoln maybe 500 miles each year anymore. Tires still look good.

Maybe tires built in recent years won't hold up like that.

Bob

[35-709]

.. But, Laurie; WHERE can YOU buy Michelin tires big enough for your big RWD Fleetwood?   I figure that they no longer exist.

You need a P235/75R-15, right... or at least a P225/75R-15.

"Fifteens" are getting hard to find.   My two '89 Caprices with the optional F41 sport suspension.. call for P225/70R-15.... and THAT is difficult.   I had to special order a set of BFG Radial T/As in order to get that size... and HUGE money!!

235R75-15 Michelins are available, you just can't get them in a white wall, UNLESS you buy them custom done through Diamondback Tires and they are indeed expensive.  Hankook and Cooper both still sell 235R75-15 narrow whitewalls although they well not be the exact correct width WW for any one particular year.

[bcroe]

I cannot believe how much worn tires are not rotated through the
spare position.  Keeping an ORIGINAL spare is so dangerous.  I
have had enough tire failures, I don't care to run them past 6 years. 
If 2 cars use the same size, but only one is driven enough to wear
out tires, I include both in the same rotation.  This keeps fairly new
tires on the little driven car, without having to buy the second set. 
Does take a bit more work with the lug wrench. 

Lately a lot of rims have rust on the outside, so they get sand
blasted and properly painted before going back in service.  I do
not see bends in the main rim structure, maybe just a bit on the
very edge.  I eyeball bend it back in place.   Bruce Roe

[Cape Cod Fleetwood]

.. But, Laurie; WHERE can YOU buy Michelin tires big enough for your big RWD Fleetwood?   I figure that they no longer exist.

You need a P235/75R-15, right... or at least a P225/75R-15.

"Fifteens" are getting hard to find.   My two '89 Caprices with the optional F41 sport suspension.. call for P225/70R-15.... and THAT is difficult.   I had to special order a set of BFG Radial T/As in order to get that size... and HUGE money!!

My '88 Lincoln Town Car calls for P215/70R-15... and I put Uniroyal Tiger Paw II (made in a Michelin plant) on it... and they're fine---nice whitewall, too!   Pricing and performance is very good----but don't make any bigger . . . . . .

The Ark is not a 'daily driver', its a show horse. Its riding on Diamond Back Classic radials, Toyo brand.
\m/
Laurie

[Mackguare]

It is for sure!

Age causes mostly dry rot in tires..

Regardless of how much care is taken, age does take a toll on tires. All the factors like UV exposure, ozone damage, and physical weathering, produce a cumulative damage with time. Moreover, an old tire is most likely to have been used for several thousands of miles, and such overuse can easily cause dry rot. However, tires can also age on shelves without ever being used, because of exposure to the elements. The inner lining of tires also deteriorates with age, due to the effect of oxidation by the air filled in the tire.

[fishnjim]

Nice discussion, brings out the gamut of how people treat and understand tires.
Mike hits it, too much to cover and explain in this space.   Like everything, tires have evolved. 
Two things, the trunk is a different environment than the road.   Probably why some period spares look good in the trunk and some explode.   If it's stored in the sun, etc then the trunk it becomes a hot box.  It's dark and good storage environment otherwise.   Tires are cured with heat to "set" the rubber, so it's "cooking" further in a hot one.   Pressure is proportional to temperature.   So if it goes in ambient at correct pressure, it could see a higher value or cycle of extremes.   Cyclic stresses are not usually good.
Rubber(s) by itself isn't strong enough for tires but forms the wear surface(tread).   The reinforcing cords determine a lot of how much strength the tire has.   If you follow the history, various materials were used.   Some successfully, some with catastrophic results.  eg;I had a set of early eagle aramid belted that "delam"ed after 20K circa '79.
Sunday I was rearranging garages, so I had a place to park my new XT5, and I moved a 2009 build date unused spare tire and rim out that came on my P/U.   I'd bought a matching alloy rim so I could rotate 5 on first tire replacement.   It's starting to get a little "glassy".  Shines and squeals when you roll it.   Even if it holds up, I doubt it has much wet grip.   So that's about the extent of "safe" tire life.   Even if it looks good, has tread, and holds air, doesn't mean it retained it's driveability.  That's where the manufacturers are coming from.

[nysdarkblue]

I had a set of UNIROYAL ROYAL SEAL tires on my 1990 Brougham. I took the car for a drive one day and the right rear tread on the tire blew off, but the tire didn't go flat. Luckily there was no body behind me when this happened. And luckily it happened when it did because I was going to drive the car with them on to the GN in Wisconsin. The tires were well over 20 yrs. old. I finally settled for a set duplicate tires of the Royal Seals from Diamondback. But now I have to show that they are accepted by Cadillac for the next Grand National. HMMMM.

[Scot Minesinger]

Laurie,

I have the Diamondback 235 r15 tires on my 1970 Cadillacs and have driven them over 30k miles, no issues in modern traffic, such as but not limited to across GW and TZ bridges in NY/NJ plus of course tunnels in Boston during GN 2013.  You should suffer no restrictions due to tires.