Tire life and date coding

[Bob S.]

Just got through watching 20/20 with a section on the date codes and useful life of tires.
I know the media has a hard time with technical issues but it brings up good questions. Their premise is that tires have a useful life of approximately 6 years and after that time the rubber becomes less flexable and you are more apt to get tread seperation.
Since most of us will not wear out a set of tires the question is how valid is there argument and how long have the replacement tires we buy from the usual sources been on the shelf before we get them.

Thoughts...

[Tom R.]

Re: Tire life and date coding

Just got through watching 20/20 with a section on the date codes and useful life of tires.
I know the media has a hard time with technical issues but it brings up good questions. Their premise is that tires have a useful life of approximately 6 years and after that time the rubber becomes less flexable and you are more apt to get tread seperation.
Since most of us will not wear out a set of tires the question is how valid is their argument and how long have the replacement tires we buy from the usual sources been on the shelf before we get them.

Valid! Much has been written on the interpretation and placement of date codes and the 6 year rule is based on the date of tire production. See the winter edition of the Restorer for an article that details how to interpret codes...well most tires that date back to the early 70's anyway.

A couple of additional facts for your consideration, European tire manufacturers have been using the 6 year guidelines since the 90's; 2nd, the bridgestone firestone recalls of 2000/2001 concluded (the studies of) that a factor was aged tires that sat perched in their spare tire stall than put into service contributed to tread belt separation. Aging factors included high heat, high humidity and improper storage. Tires were more likely to fail in Southern states than Northern states due to these factors.

Here's link to article that was published in Corvette Enthusiast on "Corvette Tire Safety."

http://www.hunt4cleanair.net/Articles/corvettetiresafety.pdf

[Duke W.]

Re: Tire life and date coding

Any tire time life is completely arbritrary. The Congress/DOT wrestled with this a year or two ago and came to the same conclusion.

Tire life starts with the design and material/manufacturing quality of the tire. Many low performance new vehicles (like so-called SUVS) come with low quality tires - they meet minimum DOT standards, but those standards are 40 years old. Such poor quality tires spend zero time on any car I own, because I would not ever buy and install them, and this list includes all of the currently available "reproduction tires". They may look OE, but they are absolute JUNK!

This is why I always recommend high speed rated tires - no less than a "H" speed rating. They start life with better design, materials and, workmanship, and the spiral wrapped nylon cap belt will prevent catastrophic failure if an internal separation occurs. I've busted several on racetracks, and they all stayed in one piece and held air. It's a quality/safety issue even if you never exceed posted speed limits.

Once built, the life the tire leads has a big effect. Tires that spend all day in the sun everyday will degrade rapidly from UV exposure compared to a vintage car that spends most of its life in a dark garage. Temperature is also a factor - the cooler the better.

A high speed rated tire in typical vintage Corvette use should be okay for something on the order of two decades.

Every time I hear "Sixty Minutes" mentioned, it reminds me of the time they used explosives to make sure the fuel tank exploded on the old Chevy pickup they "safety tested" in a side impact collision They got caught, but the program and most of the same people are still around. Amazing!

Duke

[Tom R.]

Re: Tire life and date coding

This is why I always recommend high speed rated tires - no less than a "H" speed rating. They start life with better design, materials and, workmanship, and the spiral wrapped nylon cap belt will prevent catastrophic failure if an internal separation occurs.

And the more expensive, better quality materials that go into Corvette tires is why we pay more for those as well.

[Duke W.]

Re: Tire life and date coding

I don't understand what you mean. Most radial tires that owners of vintage Corvettes buy for their cars are minimum quality non-nylon cap belted designs with speed ratings no better than "S".

Many of these tires only meet the one hour 85 MPH test at max load and pressure, which is the current minimum level DOT qualification stress test. Of course, if material or construction quality down the line drops below the levels required to pass the above minimum test, then you get a Ford Explorer fiasco and people die, but some of the dead bodies share the blame for their own demise due to poor operating and maintenance practices including overloading and not checking tire pressure.

I never ceases to amaze me how much time, money, and effort some owners put into relatively small aspects of their vintage Corvettes, then brag about the $25 tires they bought.

In your article you made references to "tire safety advocates"/"safety advocates". Do you mean self appointed "experts" such as Ralph Nader?

Who are they? What are their credentials? What is their real agenda?

Duke

[Bob S.]

Re: Tire life and date coding

Duke,
I am restoring a '59 that I am trying to keep as original as possible and still be able to drive it. This means I intend to use radial tires but would like to have the wide whitewalls. Being new, where do I find quality tires for this application?

[Paul B.]

Re: Tire life and date coding

Duke,
I am restoring a '59 that I am trying to keep as original as possible and still be able to drive it. This means I intend to use radial tires but would like to have the wide whitewalls. Being new, where do I find quality tires for this application?

Diamond Back http://www.dbtires.com/ will make you a set of wide whites from modern high quality radials. Unlike another popular brand, I've never know anyone to to be unhappy with Diamond Backs.

Paul

[Joe L.]

Re: Tire life and date coding

Duke,
I am restoring a '59 that I am trying to keep as original as possible and still be able to drive it. This means I intend to use radial tires but would like to have the wide whitewalls. Being new, where do I find quality tires for this application?

Bob------


That's the "$64,000 question". The problem is that it will be extremely difficult to find a tire in a 15" size that will have a speed rating exceeding "S". Placing even further restrictions on it (e.g. made by certain original manufacturers, acceptable tread design, exact size etc.) makes it even more difficult, if not impossible.

[Duke W.]

Re: Tire life and date coding

What Joe said. I don't know of any 205/75R-15 radials that have a speed rating higher than "S", so they lack the nylon cap belt, but Diamondback may be able to put a period correct whitewall on a 215/70 that is rated "H" or higher.

On the positive side, 205/75s have lots of load margin relative to typical driving weight of a vintage Corvette, and if you keep the TP at 32, likely no problems will occur.

The Ford Explorer tire problem had mulitple causes.

1. Many lots of tires were manufacturered with substandard materials and workmanship and did not meet even the minimum DOT standards of performance/safety.

2. To soften the ride on what was basically a truck chassis, Ford selected a low recommended tire pressure, which gave little if any load margin to a loaded vehicle.

3. Owners overloaded vehicles

4. Owners did not check and maintain tire pressure.

Rather than establishing some arbritrary useful life, Congress/DOT or the industry should upgrade tire standards. I am not in favor of specifying any specific construction technique, such as a manadatory nylon cap belt, but the 40 year old tire qualification test, which is a mere one hour at 85 MPH at design load and pressure needs to be upgraded to a test to failure with a requirement that the tire does not disintegrate.

For example the test could be upgraded to 100 MPH at design load at some fraction of design pressure - maybe 60 percent. If failure does not occur after an hour then the test is repeated with 50 percent of design pressure. If no failure occurs then repeat with 40 percent of design pressure and so on. At some point the tire is bound to fail.

Right now the only available technology I know of to keep a tire from disintegating in this type of stress test (or in the real world) is a nylon cap belt, but maybe other technology can be developed.

The key is to develop a tire that fails "soft" rather than suddently disintegrating, which often results in driver loss of control.

Such a tire will obviously cost more that the cheapest tires available, today, but safetly features have added a lot of cost to vehicles in the last 40 years, and society seems to support the effort. Nearly everything related to vehicle safety standards has been upgraded since they were first adopted 40 years ago - everything except tires, that is!

Duke

[Dick W.]

Re: Tire life and date coding

Bob, the six year figure is very valid. In my prior "life" I was in fleet management. We tracked our tires from cradle to grave. Year one thru year 4 carcass problems were almost not existant, and if they did occur you could find an underlying reason for doing so. Year five the carcass problems started increasing and by year six the curve started straight up. We kept NO carcasses that were over six years old.

I have experienced the same problems on my trailer. I did not have as much as a flat tire for almost 5 years. In year 5 (going by the date on the carcass) I experienced three separations, out of six tires. These were the not cheap Goodyear trailer specials, rather Michlein 235XR16E tires. Air pressure was checked 4 times a year so underinflation was not a problem either.

I think that anyone that drives highway speeds on a set of radials over 5 years old is taking a very big risk.

[Duke W.]

Re: Tire life and date coding

Beyond 5 years of service, the life a tire leads can make a huge difference in useful service life. Most fleet cars spend their life outside, everyday, exposed to UV from the sun, which "ages" tires much more rapidly than on a typical vintage car that spends most of its life in a garage and does not see much UV exposure.

Similarly with trailers, most in private use are infrequently used and stored outside, and the sun does its cumulative damage.

Trailer owners would be advised to keep the tires shaded. "Tire covers" are commercially available, and something as simple and cheap as cardboard cut to size and secured with cinder blocks to keep them from blowing away will go a very long way in reducing the deteriorating effects of UV exposure.

Many have problems with trailer tires. Part may be due to accelerated aging due to UV exposure and part may be due to overloading. Based on what I've seen, many loaded trailers equal or even exceed the total load rating of the tires.

I don't own a trailer, but if I did I would consider high speed-rated nylon cap belted passenger car tires beginning with the V-rated "police pursuit tires" I recommend for C3s. In addition to the 225/70R-15 100V size for C3s a 235/70R-15 102V is available, and four provide a total load capacity of about 7500 pound at 44 psi cold pressure, and the nylon cap will very likely prevent catastrophic failure in the event of an internal structural failure.

Duke

[Joe L.]

Re: Tire life and date coding

Beyond 5 years of service, the life a tire leads can make a huge difference in useful service life. Most fleet cars spend their life outside, everyday, exposed to UV from the sun, which "ages" tires much more rapidly than on a typical vintage car that spends most of its life in a garage and does not see much UV exposure.

Similarly with trailers, most in private use are infrequently used and stored outside, and the sun does its cumulative damage.

Trailer owners would be advised to keep the tires shaded. "Tire covers" are commercially available, and something as simple and cheap as cardboard cut to size and secured with cinder blocks to keep them from blowing away will go a very long way in reducing the deteriorating effects of UV exposure.

Many have problems with trailer tires. Part may be due to accelerated aging due to UV exposure and part may be due to overloading. Based on what I've seen, many loaded trailers equal or even exceed the total load rating of the tires.

I don't own a trailer, but if I did I would consider high speed-rated nylon cap belted passenger car tires beginning with the V-rated "police pursuit tires" I recommend for C3s. In addition to the 225/70R-15 100V size for C3s a 235/70R-15 102V is available, and four provide a total load capacity of about 7500 pound at 44 psi cold pressure, and the nylon cap will very likely prevent catastrophic failure in the event of an internal structural failure.

Duke

Duke-----


I really wonder how much longer those 15" "police pursuit" tires are going to be available? I don't think any police cars have been made in years that use 15" tires. Police cars tend to pile up a lot of mileage quite rapidly so I would doubt there are too many police cars left out there that use a 15" tire. When that market "dries up", I would expect the tires to be gone.

[Duke W.]

Re: Tire life and date coding

I agree. There were rumors a couple of years ago that the 215/70ZR-15 Pirelli P4000 Super Touring (an excellent C2 tire) was being discontinued, but they are still around, so I assume they are still in production, but only in a couple of sizes. Hopefully both C2 and Jaguar sedan owners (on which it was OE) will continue to support this tire, and Terry McManmon assures me that he's getting all the owner's of 15" wheel Caprice 9C1s to continue to buy the V-rated 225/70R-15 OE police pursuit tires, right Terry? (Make it the Firestone PV41 that I like best.)

Likely as the years pass the availability of high quality, high speed rated tires for vintage Corvettes will dry up, so maybe we all should consider stocking up... The situation is similar for all my cars.

A few years ago the 14" summer high performance and DOT legal racing tires that I run on my '91 MR2 went out of production. So I bought a "stash" from remaining inventory that are tucked away in my downstairs spare bedroom closest which is cool and dark. (You collect parts, I collect tires.)

For a while it smelled like a tire store (an odor I rather like), but it finally dissipated.

Last week I tried to use a "free tire repair coupon" that I had from America's Tire. The manager informed me that it was company policy to refuse repair on tires that are over six years old, which this rear Yokohama 225/60HR-14 A509 off the MR2 is, but it's otherwise perfect to visual inspection other than tread wear.

The companion front tires are still the OE 195/60HR-14 Bridgestone RE-71s, but they spent a lot of time in my garage tire rack when I ran the A008RS on the second set of OE wheels for several years. By the time the rear A509s get to cord these front tires should be down to the tread wear indicators, and I will replace them. My inventory consists for two front and four rear A509s and the same quantity of A008RS. The Deuce goes through two sets of rears for every set of fronts.

So I went to an independent tire store, and they were happy to charge me twenty bucks to dismount the eight year old A509 and install a patch.

Duke

[Joe L.]

Re: Tire life and date coding

I agree. There were rumors a couple of years ago that the 215/70ZR-15 Pirelli P4000 Super Touring (an excellent C2 tire) was being discontinued, but they are still around, so I assume they are still in production, but only in a couple of sizes. Hopefully both C2 and Jaguar sedan owners (on which it was OE) will continue to support this tire, and Terry McManmon assures me that he's getting all the owner's of 15" wheel Caprice 9C1s to continue to buy the V-rated 225/70R-15 OE police pursuit tires, right Terry? (Make it the Firestone PV41 that I like best.)

Likely as the years pass the availability of high quality, high speed rated tires for vintage Corvettes will dry up, so maybe we all should consider stocking up... The situation is similar for all my cars.

A few years ago the 14" summer high performance and DOT legal racing tires that I run on my '91 MR2 went out of production. So I bought a "stash" from remaining inventory that are tucked away in my downstairs spare bedroom closest which is cool and dark. (You collect parts, I collect tires.)

For a while it smelled like a tire store (an odor I rather like), but it finally dissipated.

Last week I tried to use a "free tire repair coupon" that I had from America's Tire. The manager informed me that it was company policy to refuse repair on tires that are over six years old, which this rear Yokohama 225/60HR-14 A509 off the MR2 is, but it's otherwise perfect to visual inspection other than tread wear.

The companion front tires are still the OE 195/60HR-14 Bridgestone RE-71s, but they spent a lot of time in my garage tire rack when I ran the A008RS on the second set of OE wheels for several years. By the time the rear A509s get to cord these front tires should be down to the tread wear indicators, and I will replace them. My inventory consists for two front and four rear A509s and the same quantity of A008RS. The Deuce goes through two sets of rears for every set of fronts.

So I went to an independent tire store, and they were happy to charge me twenty bucks to dismount the eight year old A509 and install a patch.

Duke

Duke-----


The problem is that most parts are pretty much life-unlimited with respect to age. However, apparently and based on what we've been discussing, tires are very life-limited with respect to age, regardless of use. So, that sort of bodes against "stocking up". In fact, I've got a practically new set of Goodyear ST's, installed about 12 years ago, that I was going to use for the 69 when "I get it back on the road". Now, I think I may just pitch them and go with new tires. It pains me to just pitch apparently new tires, though.

[Lyndon S.]

Re: Tire life and date coding

Joe
If you would just pitch me them their Goodyear eagle ST tires to me

Lyndon