Well I was skeptical when I first read this, but after I thought about it...

Race cars fill their tires with nitrogen... NOT because it doesn't heat up the same as room air as a lot of people believe... but because it doesn't escape the tires as quickly as room air.

According to a trade organization (fwiw), oxygen escapes through tires 3-4 times as fast as nitrogen. It doesn't give statistics for CO2 (which would have to be somewhat slower than oxygen), but it does say that nitrogen is the largest molecule in room air.

Bottom line is, it's a bigger deal for a car, since you air your bicycle and motorcycle tires before every ride anyhow, but you probably don't check your car tires daily. But yeah, I suppose now that I've read this, if I have a flat early on a long ride, I'd probably borrow someone's air pump within a few hours.