tire ageing questions answered
Posted: Wed Aug 10, 2005 9:22 am
Hello all. Once again, I called on my friend who is a tire engineer with a major tire manufacturer. I asked about the ageing issue with tires, and I attach his comments below. I call your attention to the storage of new tires awaiting delivery to tire dealers....
Best,
Ray
Sent: Monday, August 08, 2005 8:58 AM
Subject: RE: Facts about tires
Ray,
I don't think anyone knows how long a tire can last.....because too many
things, including the original technology employed, will influence
durability and resistance to deterioration.
The tire industry and NHTSA are currently looking at ageing factors due
to potential legal liability issues if a tire fails in service due to
age-related issues and to establish a "best practice" if such a thing
can be determined. A couple of Original Equipment car companies have
initiated comments in their new car literature recommending tires be
used no longer than 6 years, though I personally know of no technical
foundation for this policy and I suspect it has a "hoped for" legal
absolution for them. It is currently common practice in the replacement
tire marketplace to sell "new" tires that have been in dealer or
manufacturer warehouses for 3-4 or more years which is not a wonderful
habit ... but it has supported the virtually "trouble-free" perspective
earned by today's tires.
We all know people that are using or have used 20, 25, even 30 year old tires
with no problems.....I am one of them! Tires can work at almost any age
if used gently, inflated properly, kept undamaged, and inspected often.
If the tires have good tread depth, no cuts or localized bulges that
indicate reinforcement damage, and no surface cracking over about 1/16"
deep (evenly distributed vs. "concentrated" areas of cracking that
indicate non-uniform stress in that area) then they may work OK. However,
it is likely that an average hobbyist may not recognize when some of the
noted visual conditions have begun developing and/or accelerating which
means 2 things:
1. Constant inspection/evaluation is a must with all tires, especially
old tires. Ideally constant means virtually at the beginning and end of
every substantial usage.
2. Obviously, new tires are less likely to deliver any unexpected
deterioration and they can relieve a user's anxiety and somewhat
lessen the inspection routine.
Polyester and nylon bias tires, common until the early 70's, have a body
construction that is rather "constantly" stressed from one side of the
wheel to the other because the all of the reinforcing plies are
basically doing the same job. Radial tires, with their distinctly
different body and belt plies have an inherent stress location under the
tread edge where the radial plies (that go from side-to-side) meet the
largely circumferential belts that are only under the tread. As a result
of the construction differences, it is my opinion that bias tires age
more gracefully than radials which will almost always undergo some
internal deterioration at the stressed belt/body junction. Modern
radials are designed to accommodate/compensate for their belt edge
stresses, but under rigorous use in an aged condition I believe that
radials may be more likely to have reinforcement issues than bias tires.
When considering tires that are in the high-performance arena, all of
the prior discussion is magnified. Because high speed rated tires are
designed for that purpose, the constructions are generally more robust
in their protection against stress-induced issues, but deterioration can
likewise have more sudden impact because you cannot be looking at them
at 100+ mph.
In either construction, a tire's ability to tell you when it has a
problem is dependent on the user's sensitivity. If a smooth-running tire
starts vibrating in mid-life, something has changed. Vibrations can be a
sign of a thrown wheel weight or a separation of tire components or a
mechanical problem .... but operating with them involves risk. A tire
that makes a sound w/each wheel revolution likely has a component
separation, braking flat-spot, or localized damage. Any tire with a
localized bulge or crack has something unique going on in that location
and it needs attention. Right away. Treat a tire like a friend and try to pay
attention to any symptoms and you'll get along better .....longer.
To maximize a tire's useful life, all of the noted maintenance practices
regarding inspection, inflation, and damage prevention are very
important. Additional steps that can slow deterioration would include:
1. Storage in the dark. Sunlight attacks
and cracks rubber in all external parts of the tire
2. Keep tires away from electrical motors, air ionizers, electronic air
cleaners, etc. All electrical motors also create ozone gas that promotes
surface cracking.
3. Don't allow gas or oil contact w/tires as the rubber compounds all
include oil in their original formulas so excess oil naturally wants to
enter into the cured rubber and start softening it up again which can
cause severe deterioration and component separations.
4. Don't use petroleum-based (most of them unfortunately!) tire
shiners/dressings as their cleaning action can be twofold:
- Oils penetrate the surface just as described in #4 and chemically
damage the surface
- Light oil solvents remove waxes and anti-oxidants designed into the
rubber to prevent surface ozone cracking. These rubber compound
ingredients are what cause the gray or brown waxy build-up on tire
sidewalls and it is their to protect the rubber. These protective
materials are designed to move to the surface as tires are exercised; it
is just a shame they are unattractive. In used tire inspections it is
very common to see tires with extremely different levels of cracking on
the sidewalls because one of them has been routinely "cleaned".
These observations are purely my own thoughts and observations after 45
years as a hobbyist and 35 in the tire industry. I must stress that the
tremendous variability in tire technology between manufacturers,
technology over time, tire usage conditions, and maintenance practices
could bring other folks with my same experience to somewhat different
conclusions. Tires are not machined, easily predictable products like
many other car components. Instead, they are assembled from many pieces
of dissimilar materials into stretchy things that transfer all of a
car's dynamic capabilities to the road while being routinely abused and
ignored.. Hence, there is no advice that can ever apply perfectly to
every tire/vehicle/owner situation ..... either new or old!
Mike
-----Original Message-----
Subject: Fw: Facts about tires
Mike,
More stuff on the MG group about tire aging. As a past owner of
Bitchitlin XX's, I have an opinion, but not couched in tire engineering.
Here's the question: How long does a tire last with respect to aging?
What effects the tire while stored?
Best,
Ray
"Conlige suspectos semper habitos!"
----- Original Message ----- From: "Mike Duvall" duvallcom@sbcglobal.net> To: mg-t@autox.team.net> Sent: Thursday, August 04, 2005 12:43 PM Subject: Facts about tires > Anyone have any evidence of the age of a tire being a problem or is this > speculation?. I can understand a tire from the 60 or 70s cracking and > getting old but tires made in the 80s and 90s have to be made of better > materials. These marketers like to put the fear of God into you to sell > you anything new. > > Please don't respond with opinion and your life is at stake and all the > rhetoric, If anyone can reference a location on facts, I would appreciate > it....(preferably not a manufacturer's site) Something independent... > > Mike [Non-text portions of this message have been removed]