I bought a set of 4 new Nankang NS20s and the guy at the new local tore store told me he doesn't think I need nitrogen in them. I used to run nitrogen. I used to seem to have tires that needed be be topped off with air every 1-2 months and the nitrogen seemed to help seal the tires and lessen my need to top them off so often. These tires have been on for 6 or 7 weeks and I don't think I've lost one pound yet. Thanks to this place I saved $100 on these tires and will spare myself of the $25 for nitrogen. As long as they hold their pressure, I'm fine with dry compressed air.