In critical applications tires are inflated using pure nitrogen (link).
Nitrogen molecules have a more difficult time escaping through the microscopic spaces that exist between a tire's rubber molecules. [...] Nitrogen reduces the loss of tire pressure due to permeation through rubber over time by about 1/3. (source)
According to WebElements, nitrogen bond length (109.76 pm) is smaller than oxygen bond length (120.74 pm), so why nitrogen permeation through rubber is said to be lower than oxygen?