Re: Continental Gatorskins get ugly

In article <slrnf16l9g.oc.spamspam@xxxxxxxxxxxxxxxxx>,
Ben C <spamspam@xxxxxxxxx> wrote:

On 2007-04-04, Michael Press <rubrum@xxxxxxxxxxx> wrote:
In article <7086549.DGCGfL6n0x@xxxxxxxxxxxxxxxxxx>,
G?nther Schwarz <strap@xxxxxx> wrote:

Michael Press wrote:

I do not like hand pumps, even floor pumps. I do not want to
maintain an air compressor. What inflation scheme do I
use?

Petrol stations? The adaptor for filling with Presta and Dunlop valves
lives in my wallet.

I keep an 80 cubic foot (2.25 m^3) tank of compressed
nitrogen, with a regulator and a hose with a valve and
presta head. Set the regulator and fill the tires. I
also put N2 in the air space of half empty wine bottles.

Do you find the tyres hold their pressure for longer using pure
Nitrogen? There's some theory about partial pressures I half-remember
that never seemed to make much sense in the first place; but it's
claimed that truckers fill their truck tyres with Nitrogen, possibly to
reduce corrosion.

I do not know about longer. I put in 115-120 psi, then
let the pressure drop to under 90 psi, then repeat. The
cycle is about 2-3 weeks.

Suppose we started with tires inflated to running
pressure with pure N2. The ambient atmosphere is about
18% O2 with some H2O and CO2. The tubes are porous. O2
etc will leak _into_ the tube. The the process is
osmosis. If the tire were inflated with SF6 (sulfur
hexafluoride) the SF6 would leak out so slowly and the
atmospheric gases leak in so quickly that the tire
could pressure could rise above the initial inflation
pressure by about 1 bar. Since I top off the tires that
are at equilibrium composition with the ambient
atmosphere, the osmotic effect is likely negligible.

Some racers use N2 to attain finer control of pressure
as the gas changes temperature. When inflating with a
compressor you get whatever the inlet sucks up including
H2O, CO2, and various hydrocarbons, all of which have
very non-linear responses to pressure and temperature
changes. Those in the compressed gas trade call CO2 a
`wet' gas.
--
Michael Press
.

Relevant Pages

  • Re: (Small) Tire Science? Contact Patch Wrinkles?
    ... Low pressure, high pressure. ... Given a wide enough range of inflation and load. ... thin tires on 700c rims because those rims can't handle high inflation ...
    (rec.bicycles.tech)
  • Re: (Small) Tire Science? Contact Patch Wrinkles?
    ... Low pressure, high pressure. ... Given a wide enough range of inflation and load. ... thin tires on 700c rims because those rims can't handle high inflation ...
    (rec.bicycles.tech)
  • Re: Tire Inflation Levels
    ... My tires are inflated to 50psi because well, ... you should inflate your tires to the pressure recommended by the ... already recommend a pressure that achieves the best mileage (becasue ... "Proper inflation is the single most important part of tire care. ...
    (alt.autos.toyota)
  • Re: Why nitrogen?
    ... Air is around 78% nitrogen anyway, ... so pressure stays more predictable. ... We bought a new Toyota and the salesman stated the tires were filled with N2 since the molecule was larger and less corrosive than air which contained O2. ... I did buy a small compressor for the hangar, but never really used it that much. ...
    (rec.aviation.piloting)
  • Re: 2002 Corsa Air Con
    ... Then I read the pressure on the gauge which I expected to read low ... compressor it self doesn't spin. ... compressor doesn't spin give it half a tin of gas to 'kick start' it. ... You could easily defeat the LP safety switch to run the compressor, ...
    (uk.rec.cars.maintenance)
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