Oxygen in tyres vs Nitrogen

[belalegosi]

i have seen at certain shops where a vacuum machine is used to remove normal air before installing the nitrogen. my only concern with this is that the tire is sucked-in which in my opinion can cause damage to the tires. also it is to be noted that most shops who install the nitrogen checks and if necessary inflates your nitrogen inflated tire for free provided that their did the installation.

again, how do you completely remove all the air from the tire with only one valve stem?
Vacuuming would remove some of it, until you break the bead on the tire/rim.

To properly run nitrogen, you need two valve stems to flush the air out.

[Kongorealm]

^agreed!
I have seen shops do this with only one valve stem, their suck out the air from the tire until it deflates and the tire looks like its about the cave in. Not something I would personally do as it looks damaging. it was an observation.