I read in the news paper aout "liquid Nitrogen filed in tyres instead of air"

It is but the problem is that nitrogen isn't available at every service center. So, if you need to fill it up again, then what? I hope the tyre won't get puntured too!

We tested the liquid nitrogen and pitted it against natural air for the tires. Both cars, filled with 30psi and one test was the city driving. cars drove for 3 hours in city routes, Air pressure for both cars didn't change. Next test was long driving. 8 hours drive, out of town route. Here is where the liquid nitrogen really shines. No drop at air pressure on the full drive. Natural air showed a decrease in pressure. This is because the molecular structure of the nitrogen is bigger than natural air. Which makes it hard for the nitrogen to seep out of the rubber. Unlike natural air, which has smaller molecules, which can easily pass thru the tires rubber when running and gaining heat. So it would be best to get natural air if your car will only run short distances r for city driving, but if you travel far all the time, liquid nitrogen can save you some tire mileage costs.

You could run a vacuum over the seats and carpet in a car and remove several times the amount of weight of the air in the tires. Art

Yes things like this is what is putting our auto makers out of business. It is just something to charge more for. That is the case with all the bells and whistles they are putting on them. They put some junk on a car that costs them a couple hundred $ and up the price of the car $1,000. In doing this they have just flat priced themselves out of the market. Art