<VV> Comments On Old Tires

[Smitty Smith]

Smitty Says:  In one of my many disguises, I sold tires when I was young.  Even went to school to learn about them.  One thing I remember that may have a major impact on old rubber failing is a thing called a "standing wave".  At some speed and increasing with speed, the tire smacks the pavement and rebounds.  At the same time the part of the tire that was carrying the weight snaps back round (so to speak) and even goes beyond round.  The two together create a bulge in the tread right behind the contact patch.  This bulge of course snaps back in and over travels again.  This action continues for maybe up to 8 inches behind the contact patch.  When you see it in photographs it looks like a flag waving in the wind.  How much standing wave you get depends pretty much on tire pressure.  Anyway it stands to reason that if you run aged tires on the street at 35-40 mph you are relatively safe.  But you take them out on the highway and expect the hardened rubber to keep up with
 that high speed flexing, you may lose the tread.