Tires: tire dry rot, passenger car tires, pressure tires

Question
what causes tire dry rot?

Answer
Patty,

Cracking is a natural result of the rubber aging process.  The rate at which tires age depends on many factors:

Temperature:  The climate in the area where you live has a major impact on the rate.  Some quote the Arrhenius equation (wikipedia that!) that says that chemical reactions double with every 10 degree Celsius increase in temperature.  Also operating temperature should be included - I'll discuss that later.

Strain:  That's the amount of flexing that takes place.  Fundamentally this is all about inflation pressure.  Tires naturally leak air both through the tire itself and at junctions where 2 different air holding components meet - such as between the tire and the rim and the rim and the valve.

Strain also increases the operating temperature.  So it is important that inflation pressure be checked regular - "they" recommend once a month.

Stress:  This is more or less a load on the tire kind of thing.  Pickup truck tires would be more prone to stress than passenger car tires.

Speed:  More speed increases the rate of heat generation within a tire and therefore its operating temperature.  Not to mention the stress caused by centrifugal forces.

Time:  Recent bulletins from the tire manufacturers seem to point to between 6 and 10 years after the manufacturing date as the point when you should replace tires - and the different between the extremes is related to the climate you live in.

There are other factor that play a role - such as how "spirited" your driving is, but they are minor.

Primarily, then, this boils down to 4 things - 1)  The climate where you live, 2) the amount of inflation pressure you put in the tires,3)  how you drive, and 4) how old the tires are.