Checking filled tires pressure

[ning]

I went to check my rear - filled with scrumptious beet juice - tires.

I parked with the valve at the top last night. Today I figured, press the button to eject what little juice may be left in the valve, check pressure, then fill.

I got about half a cup and stopped.
Did they fill the tire completely? I thought they left an air space?

 

[oldnslo]

There is supposed to be a little airspace but it could be filled slightly above the stem.

 

[RayIN]

Filled tires should be checked with stem on the bottom; which requires a different air gauge.
The normal fill is 70%. That is approx. level with the stem; completely filled is not good.
Jack up that wheel position, then check air pressure.
The usual air pressure is 18 PSI for a filled tire.

 

[ericm979]

Mine did the same thing, mostly on one side. I let some beet juice out.

Even with the special gauge I find that I have to rinse out the gauge immediately or the beet juice will start drying inside. I carry a pan of warm water out to the tractor.

 

[ljgordon]

Filled tires should be checked with stem on the bottom; which requires a different air gauge.
The normal fill is 70%. That is approx. level with the stem; completely filled is not good.
Jack up that wheel position, then check air pressure.
The usual air pressure is 18 PSI for a filled tire.

I was 100 feet from him when he said it.

 

[hube2]

Mine did the same thing, mostly on one side. I let some beet juice out.

Even with the special gauge I find that I have to rinse out the gauge immediately or the beet juice will start drying inside. I carry a pan of warm water out to the tractor.

With the proper gauge it does not matter where the stem is with the proper type of gauge.
Yes, you must rinse the gauge thoroughly after use or it will become plugged up and useless.

If the pressure is low the weight of the tractor could squash the tire a bit causing the liquid level to be higher than the stem positioned at the top of the wheel.

With a standard gauge I would put some air in it and then to see if I could get it to stop squirting fluid and then let some air out if there is too much rather than try to check them if they could be low.

 

[ning]

I set the inflator to 18psi, turned it on and hooked it up and ran it till it was full. Took a couple minutes but not long.

I had a hose extender on it; removed it after and cleaned it; no sign of juice before it.

 

[jwmorris]

Why not get an oil/fuel pressure gauge and put a chuck on it?

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[oldnslo]

Curious where the 18 PSI came from for filled tires. Last time I checked pressure was determined by tire size not by being filled.

 

[ning]

My understanding is that since there's less air volume to provide shock absorbance, you need to treat the tire differently.

Consider the degenerate case where there's just a spec of air space - virtually the entire tire is filled with fluid. Since the fluid is mostly incompressible, the tire is going to ride really hard.
Ok, that's a degenerate case. Now, decrease the fluid by a cup, add just a bit of air.

Will the tire be bouncy now? Barely. And, if you run 30psi in that one cup space of air, you can barely compress that one cup of air before it's pushing back really hard.

Now at 20% air, 80% fluid, the tire isn't going to behave like you want it to if that 20% air is at (100% of tire full of air) pressure, because every bump on the tire is only acting on the 20% of the volume which is compressible since it can't mess with the fluid.

You have to put less air in, so that the entire tire behaves right... or at least, closer to right.
My guess is that even at 18psi it's still probably going to ride harder than an all-air-filled tire.