The dry rot on the surface of this tire is indicative of what is happening inside.
Before paying $40 a piece to fill your car’s tires with nitrogen, it might be best to understand what’s really happening. The air around you is already 79 percent nitrogen, according to TireFactory.net, but squeezing that last bit of oxygen and water vapor out can have some surprising advantages.
Nitrogen atoms are physically larger than oxygen atoms. Small oxygen atoms have an easier time of squeezing between the tire’s molecular matrix, causing the tire to lose air pressure over time.
The moisture content of normal air can cause it to expand under high temperatures and contract when cold. This can cause poor traction during winter and excess tire wear during summer.
One proposed benefit for nitrogen filling that having the proper air pressure at all times can net gains in fuel economy by reduced rolling resistance.
Pressurized oxygen has a way of eating (oxidizing, dry-rotting) rubber. Eliminating oxygen from the air is said to reduce this internal dry-rotting.
Vehicles that spend a lot of time sitting in storage can probably stand to benefit from the inertness of nitrogen gas, which helps to maintain the tire (especially in humid conditions).