5 Series E60 520d (N47) SAL
36 0106 (251)
Inflating tyres with nitrogen (N2)
The question is regularly asked, whether inflating the tyres with nitrogen instead of air has
any benefit with respect to a "gradual loss of tyre pressure". This process is also known as
diffusion (diffusion is the movement of miniscule particles, especially atoms or molecules).
Some companies regard inflating the tyres with nitrogen as a way of selling the customer a
feature that has no practical benefit whatsoever with respect to diffusion. As nitrogen has
larger molecules, it would indeed be logical to argue in favour of inflating the tyres with
nitrogen instead of with air. However, the improvement achieved is only marginal because
air is anyway made up of about 78 % nitrogen.
Composition of air:
78 % nitrogen (N2)
21 % oxygen (O2)
<1 % inert gases
0.03 % carbon dioxide (CO2)
The reduced rate in the drop in pressure inside the tyre is just a few hundredths of a bar
over several months. Inflating the tyres with nitrogen does not relieve the driver from his
duty (described in the Owner's Handbook) to check the tyre pressures regularly. Nitrogen is
used in aviation and in motor racing because, in the event of an accident and the
associated risk of fire, no additional oxygen should be fed from the tyres.
BMW does not recommend inflating tyres with nitrogen. Should individual customers wish
to have their tyre inflated with nitrogen, their wishes may be accommodated.
SI Inflating tyres with nitrogen (N2) All series
BMW AG - TIS
Issue status (12/2007) Valid only until next DVD is issued
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