Weight of air vs. Nitrogen

So I made an amazing discovery today. I got my new Sailuns partially installed today (so far). When I took the old tires and rims to Discount Tire, they were easy to lift and move into my truck. When I picked up the new Sailuns they were really heavy. Same rims. The old had nitrogen and the new has plain old air. So it must be the air.


Sure it has nothing to do with going from an F rated tire to a G rated. :B