Here is an interesting article about tire aging
http://www.safetyresearch.net/tires.htm
Many automobile manufacturers are now printing in the owners manuals that
tires should be replaced after 6 years reguardless of tread wear.
---- Dave & M <rusd@sitestar.net> wrote:
> Hi Terry,
>
> There is little doubt that the tire aging process starts as soon as
> they are manufactured & is "the start of a clock". Tread hardening, &
> tread
> separation are the most common problems associated with aging. ---
> This hardening is actually a slower extension of the original
> vulcanizing process which is used to harden the soft green rubber to
> it's intended hardness when it is manufactured. It never stops.
>
> How long it takes to harden a tire to unsatisfactory traction or
> safety levels, depends on temperature, amount of ozone exposure, &
> amount of ultraviolet exposure, both during storage & during use. As
> Ed said, tires age even while on the shelf.
>
> On the tread separation/safety issue, several European car
> manufacturers recommend a tire age limit of around six years, & Ford &
> Chrysler have recently adopted a maximum tire age recommendation of
> around six years.
>
> I had to temporarily reinstall my 10 year old tires which measure 80
> on a "Shore A Scale" durometer. Another set of relatively new
> Michelins, at the time, measured 60 on the same scale. The loss of
> traction when cornering & on wet roads was very obvious with the
> harder tires.
>
> To put the Shore A Scale in perspective, my thumb nail measures 97, the
> underside of my thumb measures 50. Some very soft "race only" tires
> can have a "Shore A" hardness of 30 to 40.
>
> In summary, I believe that measuring the tires changes in hardness
> over time is a good way to determine if the tire has aged to
> unacceptable levels where tread separation may become a problem. If
> you do not monitor tread hardness changes, the six year rule is a safe
> compromise. An increase of 25% hardness from original would likely be a
> cause for serious concern.
>
> Regards,
> Dave Russell
>
>
> TERRY COLL wrote:
> > I'm still wrestling with this 5 or 10 year tire limitation. What exactly
> > happens to the tires and what exactly causes it? Does it apply if the tires
> > have been stored inside and not exposed to sunlight?
> >
> > Terry Coll '64 BJ8
> _______________________________________________
> bighealey@charter.net
>
> Healeys@autox.team.net
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