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Display Mesage #111264

Nitro Fill?
Written by alfr4d on 3/13/2012 at 01:00 pm

--- In, "boysrus_racing" <boysrus_racing@...> wrote:
> I have and use nitrogen in my shifter kart tires, but I've not filled the PC
tires with it.
> Nitrogen greatest benefit is that it is dry and so doesn't expand like air. A
kart tire going from 70 degrees to 240 degrees may gain 10 or more psi using
air, but only maybe 3 psi on nitrogen. When we start with, for example, only 9
psi, going to 12 psi is going to change handling, but nothing like going to 20
psi would do (initially bind the chassis, then overheating the tire and
decreasing traction, eventually blistering the tire)! It is much easier to
control pressure, therefore the tire's contact patch and heat, using nitrogen.
> Bike tires heat up more on the street than a typical automobile radial tires,
but nothing like the temp changes in a racing environment where nitrogen is a
must-have. Street-driven MC tires get warm to the touch, so may go from 70 to
110 degrees, but as such will not have the potential for significant pressure
gain that nitrogen would help control.
> That said, nitrogen is easier on rubber than air, and is a larger molecule so
tends not to leak out as quickly. The downside is that it is inconvenient for
most folks, possibly costly and probably isn't going to provide any noticeable
performance or longevity benefit if pressure is checked regularly (monthly).
> If you choose to use it, you need to fill and purge the tire at least a couple
of times to get as much air as possible out of it. You are not going to get the
benefits by just adding a few PSI of nitrogen to a pressurized tire.
Preferably, purge the hose before filling the tire. Remember that nitrogen is
heavier than "air", so when purging the tire, keep the valve stem at the highest
point possible.
> As I said, though even though I have ready access to it, I don't bother to use
it in my street cars or bikes.
> Bob
> --- In, "dave_hiett" <dehiett@> wrote:
> >
> > Anyone done the nitro fill on your tires? Any difference in performance or
tire life?
> >

Home science tells me:

Nitrogen (N2) 78%
Oxygen (O2) 20%
Inert gas 1%
Carbon-dioxide (CO2) 0,03%
Water H2O 0,97%

Water can be present for up to 4 percent.

First conclusion is that air is in fact Nitrogen for the bigger part. Oxygen can
be corrosive but I am surprised to read that it will expand that much more in
heat. I guess that rubber is like a balloon when it is hot and the tires are
being centrifuged. Cold nitrogen will be heavier but gases pretty much weight
the same, no complaints here. The greatest difference is the amount of water in
the air, just because nitrogen is dry and filling air from the compressor
outside usually is very much not and can also bring liquid water in the tire on
rainy days, shortening its live. Wet air is also difficult to heat up and may
not be cooling the rubber equally efficient. This is also true for heating the
house in winter. Dry air is more comfortable and saves you money.

Reading about Nitrogen in tires always comes down to the largest benefit of the
air being so dry. Some mention a decrease in molecule loss, leaking trough
material, but Nitrogen is bound to stay inside with this kind of loss and tire
pressure may drop anyhow.

Another big difference is the color of the valve cap. Green. It will be a solid
warning for anyone not to fill the tire with the recommended pressure and to let
its pressurization be the concern of somebody else. Always waiting the
opportunity. Even with an own expensive filling station at home or possible
smart ways to get Nitrogen in the tire, like a compressor filled with it, this
color cap will always be looking like the rider is taking the wrong measures.

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Message Thread for message #111264