The 4 PSI Rule For Tires: What Is It, And Is It Reliable? - Jalopnik

The 4 PSI rule compares cold and hot tire pressures to estimate proper inflation, but its reliability depends on driving conditions and tire type.

Every rotation bends a tire's sidewall, and that repeated bending is the source of the friction that builds up inside the rubber a process engineers call hysteresis. That friction doesn't disappear; …