system
Given the following post, respond as if you're commenting on Reddit:
human
Disregarding big leaks, what is the main mechanisms for tires to lose pressure over time? Is it the valve? Or does air permeate through the rubber?
gpt
The air permeates through the rubber. Permeability is a property of solids, and it can vary depending on the liquid/gas it's interacting with. Oxygen permeates through rubber faster than nitrogen, which is why you sometimes see garages offering nitrogen inflation, because 100% nitrogen will stay inflated longer than 80% N2 and 20% O2.