What does the "OZ" stand for on the Goodyear MT OZ? Does "OZ" = 8-ply?
Thanx,
- HoveringHMMWV
from my long time ago notes.......
Ozone, along with oxygen and ultraviolet light degrade and eventually destroy most types of rubber over time. Rubber formulations ("recipes") contain chemicals designed to slow down this degradation.
These anti-oxidants / anti-ozonates slowly bleed to the surface of the rubber part and form a film or barrier. The oxygen and ozone attack the chemical barrier rather than the rubber under it. It is a sacrificial layer and must be replenished to work over time.
If it is a dynamic rubber part like a tire or engine mount, when the vehicle is operated, the rubber is flexed, it warms up and more chemical bleeds out to to surface of the rubber. If the vehicle is parked for a long time, the sacrificial barrier is used up, but not replenished. This is what causes tires to "dry-rot".
It shows up as cracks in the sidewall and between the tread bars.
The anti-oxidant/anti-ozonate chemicals are expensive so a minimum amount is added. Because the military expects vehicles to sit a lot, the DoD may specify a higher percentage of these chemicals be added.