-----Original Message-----
From: drpepper <drpepper@nacs.net>
>Is there some sort of formula to determine how much/many times you can add
>air? I'm assuming it is based on PSI, temp, and humdity.
Sure there is, straight out of high school physics: Pressure time Volume is
proportional to Temperature.
Volume is easy -- you know the volume of the tank, and you can figure out
the volume of the tire. Figure initial temperature in the tank and in a
cold tire is the same as the outside air, and probably won't change
radically during the exchange of air. Now you can figure out how many times
you can bring the volume of your tire to a given pressure. Keep in mind
that the pressure in the tank has to be higher than the pressure in the tire
to fill it.
Practically, I've found I have just enough air in a 7-gal tank charged to
125psi initial pressure to bring all four tires (225/50-15) from around
35psi to 50psi. Or to bring two of them up (since I run the rears at street
pressures anyhow) and have enough air to do all the tweaking I need.
>What are good gauges? What should I look for and how much should I expect
>to pay?
A good guage is any which gives you a repeatable result. A short hose with
a bleed valve is nice. I got one through ImParts in St Louis
(www.imparts.com) for about $20.
>I'm a newbie to the land of the cone but, wouldn't calibration be sorta
>subjective? If your gauge is "off" but you are running fine wouldn't you
>just use those numbers the gauge gives you since you have no objective
>real-time comparison.
That's true, but how do you know when the guage is no longer delivering the
same reading at a constant pressure? Which is the other reason we
recalibrate measurement devices.
>Do you have to pay for this? I'm sure that some places might get sick of
>seeing me pull up with my big red bottle every weekend. I'm also assuming
>that you empty the container fully after every event? How do you keep/get
>moisture out of the tank?
I just go to the gas station -- I've never had anyone chase me away from the
air hose. The time you're tying up their air compressor is miniscule
compared to the volume of "regular" traffic coming through.
You'll only bleed the tank down to equal your tire pressure, if that. These
tanks can store air a low pressures (125psi is low pressure) indefinitely,
but they'll probably lose a little pressure between events due to
temperature variations and very slow leaks around the valve assembly. You
won't keep moisture out of the tank, any more than you keep it out of your
tires. But if you're worried about corrosion in the tank, don't. Never
seen one fail for that reason yet.
Jamie
'92 Prelude Si
Speed Demon Racing
http://www.mindspring.com/~jsculerati/sdr
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