checking tire pressure with fluid in them

v. kangas · Jan 27, 2012

tell me why they say to have valve on bottom when checking pressure

LPgas only · Jan 27, 2012

valve needs to be on top so it does not mess up the gauge so fast.

Anonymous-0 · Jan 27, 2012

The way I heard it was to have the valve on the top so you don't get liquid into the gauge.

nickg · Jan 27, 2012

who told you that is wrong. you want the valve on top. That is wear your air void is so you can see what your pressure is and air your tires and not leak fluid every wear.

Stuart · Jan 27, 2012

You either have to have a liquid capable gauge or have the valve stem on the top and use an air gauge.

bobs old iron · Jan 27, 2012

sounds wrong to me..take a bottle of pop, turn up side down,, where is the air every time you rotate bottle,,,law of physics and gravity..get the idea...valve stem up top with air...think i'm right, other wise i'll be told different...

rustred · Jan 27, 2012

probably due to the hydrostatic pressure of the fluid. but i check from the top not to buggar my guage. need a special guage for btm checking.

Mike M · Jan 27, 2012

Put valve to the top and shoot some air in FIRST to clear the water out of the way then check the pressure. They do make gauges that say for use with fluid filled tires on them. Rinse it out and dry and oil it after each use too.

v. kangas · Jan 27, 2012

j.deere manual says valve should be on bottom.it did'nt make sense to me but have'nt had experience with this. thanks to all for help.

rustred · Jan 27, 2012

to be real technical you should have slightly more presure at btm. does not matter where you check pressure.think of the divers, the deeper they go the more pressure. its if you have the proper guage.

Vernon in Ks · Jan 27, 2012

Well there you go. Jd wants to sell you a tire guage

JMOR · Jan 27, 2012

Where do you want to know the pressure in your tire? Top or bottom?

justanothercase · Jan 27, 2012

Valve on top so when the core falls apart you have a chance to save some of your fluid.

ss55 · Jan 27, 2012

That's true! Plain water is about 1/2 PSI per foot of depth. That's 1 1/2 PSI from the top to the bottom of a 34-38 inch rim. Calcuim cloride will increase that difference.

Check fluid filled tired with the valve stems in the same positions if you want equal tire pressures.

showcrop · Jan 27, 2012

I roll the stem up to the top, and after checking I add little bit of air even if it isn't called for in order to blow that couple drops of CaCl out of the valve.

John A. · Jan 28, 2012

v. kangas, I don't know or care who put out this totally wrong info!......
1 rotate the wheel till the valve stem is @ 12:00 position,
you can use either a liquid tire gauge or a standard air pressure gauge. You just need to rinse out the CaCl so it doesn't rust up the tire gauge.
2 use the little pointer on the back side of the head of the tire gauge to clear the few drops of liquid out of the valve stem.

3 Them check the tire pressure just as usual on any tire.
Later,
John A.

Anonymous-0 · Jan 28, 2012

Did JD say why?

Texasmark1 · Jan 28, 2012

The hydrostatic pressure is a small part of the tire pressure. The air and the water share the inner chamber of the tire which is fixed. The water doesn't compress so it is a fixed volume, the air does. So when you air up the tire, you are airing up the area where no water resides and that's it.

Put the valve at Noon, blow it out and measure your pressure.

Mark

Owen Aaland · Jan 28, 2012

The hydrostatic pressure of water add .433 PSI per foot of water depth. CaCl mixed with water can add almost 40% more to this.

If the fluid level in a tire filled with CaCl fluid is two feet above the valve stem the added weight will add about 1 1/2 PSI to the pressure reading when read at the 6 o:clock position versus the 12 o:clock position.

Texasmark1 · Jan 28, 2012

The hydrostatic pressure is still a small part of the pressure of
the tire. It is approximately 1/2# per foot of altitude as you said
(.433) but if I am going to pump my drive tires to 18 or so #'s
and my tires are 1/2 or so full, being 3' roughly as you said (1 to
1.5#), Then for 18# fill it is only give or take 5-8% of the
pressure and for 20 or more #, less than that. So what is the
point of this? We already covered this ground.

But the hydrostatic pressure is just the potential energy
(potential work function) of the water on/at the ground, amount
in psig as you said, as a result of how far up the tire you want to
measure it. If you completely filled the tire with water (liquid)
they would only register a couple of # of hydro press. and ride
like concrete as water cannot be compressed as air can.

Like if you have a community water well and a 100' stand pipe,
at the bottom of the tank you could plumb a faucet and have
43.3 psig static pressure available till the water in the tank starts
to drop. The actual weight of the water is not considered in this
calculation.

Like on one of my tractors I have 55 gallons of liquid in each tire
weighing about 413 # dead weight, but that's not what the tires
are pressurized to.

Are we done?

Mark

v. kangas · Jan 30, 2012

thank you Texasmarkl.it makes sense to me now.

checking tire pressure with fluid in them

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