Loaded tire pressure

[Soundguy]

Never said the PSI was different...simple physics...you guys are misunderstanding the point I'm trying to make. Yes, the PSI is the same, but it changes the physical properties of the tire. The air container (tire) is fundamentally smaller (volume).

no it is not... the tire csing size / volume has not changed any. each internal square inch of that tire will have effectively the same pounds per square inch exerted on it whether it is a square at the top in the air bubble, or a square out on the side wall under fluid.

think of a well pump with bladder.. that bladder with compressed air is what gives you water pressure when the pump is not running.. the pressure of that air pressing on the bladder, pressing on the tank and pipes.

the reduced air volume only means there is less amount of give available as the amount the air can compress is reduced since the volume is reduced.

This makes for a smaller interior surface for the pressure to exert on. It does, in essence, create the effect of a smaller tire. It's not that hard to understand...you are overthinking a simple question of physics.

nope.. sorry.. same size tire. the imersed part of the tire is not immune from pressure just because it has a liquid over it.. that's why you don't fully load a tire as if it hit a shock load it could split.. no compressible material in there to take a shock load like air would.. the tire splits due to psi on the interior of the tire exceeding the burst rating of the tire...

I wear a size 11 shoe...it fits my foot...if I try to put my foot in a size 10-1/2, it will fit, but it exerts more pressure over the surface area of my foot and makes it uncomfortable...because I am trying to place the same volume of foot into a smaller vessel.

that analogy don't work with the tire, ballast and air pressure we are working on....

And I agree with rick.. you are debating useless minutia by keep bringing up the difference in compressability of the liquid in the tire, vs the air in the tire.. and in effect, diluting the otherwise practical information in this thread.

soundguy

 

[mustangsallysdad]

no it is not... the tire csing size / volume has not changed any. each internal square inch of that tire will have effectively the same pounds per square inch exerted on it whether it is a square at the top in the air bubble, or a square out on the side wall under fluid.

think of a well pump with bladder.. that bladder with compressed air is what gives you water pressure when the pump is not running.. the pressure of that air pressing on the bladder, pressing on the tank and pipes.

the reduced air volume only means there is less amount of give available as the amount the air can compress is reduced since the volume is reduced.







nope.. sorry.. same size tire. the imersed part of the tire is not immune from pressure just because it has a liquid over it.. that's why you don't fully load a tire as if it hit a shock load it could split.. no compressible material in there to take a shock load like air would.. the tire splits due to psi on the interior of the tire exceeding the burst rating of the tire...




that analogy don't work with the tire, ballast and air pressure we are working on....

And I agree with rick.. you are debating useless minutia by keep bringing up the difference in compressability of the liquid in the tire, vs the air in the tire.. and in effect, diluting the otherwise practical information in this thread.

soundguy

I could put my engineering cap on and explain this to you, but I believe we may have maxed out your capacity. (Air, considered a liquid as far as compressibility, and viscous liquids compress at different rates). Put your thinking cap on and think about this for awhile before responding again. You are arguing just for the sake of it. I've tried to explain this in layman's terms, but you are not grasping the concept. Read your prior post to this...you agreed and disagreed with me in the same paragraph. You are way overthinking this.

 

[RickB]

You'd lose that bet...I CAN DEFINITELY tell the difference between a loaded vs. non loaded tire if the given pressures are the same. That is why I have loaded tires with 10 PSI loaded vs. the 20 PSI that I ran unloaded. Do we all need a group hug or something? LOL.

If you know ahead of time which you are driving, it's not a blind comparison, now is it???

You are projecting what you think you know into a predetermined result. I'm sorry I challenged you that way, I could have predicted your response had I thought about it a little.

Additionally, if 10 PSi is near correct for loaded tires on your tractor, 20 psi unloaded was way overinflated.

No hug required.

 

[sevilla]

I know that was a vague point...let me try again. Diesel is a liquid and you know what ignites it in an engine...compression. I wasn't trying to go off topic, but somewhere earlier in the thread there was mention of liquids not compressing. That was incorrect, and this forum stuff is all about learning from one another.

In a diesel engine it is the compression of the air and the consequent increased temperature that ignites the fuel which is injected after the air is compressed/heated. Compression of air functions as a spark.

 

[mustangsallysdad]

If you know ahead of time which you are driving, it's not a blind comparison, now is it???

You are projecting what you think you know into a predetermined result. I'm sorry I challenged you that way, I could have predicted your response had I thought about it a little.

Additionally, if 10 PSi is near correct for loaded tires on your tractor, 20 psi unloaded was way overinflated.

No hug required.

No Rick...20 PSI is the recommended pressure on both the sidewall and in the owners manual.

 

[mustangsallysdad]

In a diesel engine it is the compression of the air and the consequent increased temperature that ignites the fuel which is injected after the air is compressed/heated. Compression of air functions as a spark.

So the hydraulic fluid in your tractor...under pressure, it guess it remains cold to the touch when under pressure. Diesel fuel, under compression heats up...it has a flash point. How many hydrodynamic engineers on here, anyway?

 

[Soundguy]

I could put my engineering cap on and explain this to you, but I believe we may have maxed out your capacity. (Air, considered a liquid as far as compressibility, and viscous liquids compress at different rates). Put your thinking cap on and think about this for awhile before responding again. You are arguing just for the sake of it. I've tried to explain this in layman's terms, but you are not grasping the concept. Read your prior post to this...you agreed and disagreed with me in the same paragraph. You are way overthinking this.

I have my engineering degree.. and know that you are beating a point of minutia to death and back many many times... this went way past practical application long ago.

any usefull information is now burried in the first few posts, and the rest of it is just statics and dynamics that the average hayseed doesn't care about.. or will -ever- need to know.

what they need to know:

air the tire up after you do the 70-90% fill, depending on whose chart you use, add air till the tire deflection and ground patch look good.. should be close to air pressure needed for an un ballasted tire, not counting loads on the tractor.. don't exceed tire or tube max pressure.

what they don't need to know:

ANY of the MATH about the compressibility of a fluid or liquid .

soundguy

 

[sevilla]

So the hydraulic fluid in your tractor...under pressure, it guess it remains cold to the touch when under pressure. Diesel fuel, under compression heats up...it has a flash point. How many hydrodynamic engineers on here, anyway?

Everything under pressure increases its temperature. It is a fact that in a diesel engine the fuel is injected after the air is compressed (Diesel engine - Wikipedia, the free encyclopedia). That is how a diesel engine works.
A fluid does not reduce its volume under pressure i.e. it is non compressible. That is why a loaded tire needs air to prevent bursting.

 

[mustangsallysdad]

I have my engineering degree.. and know that you are beating a point of minutia to death and back many many times... this went way past practical application long ago.

any usefull information is now burried in the first few posts, and the rest of it is just statics and dynamics that the average hayseed doesn't care about.. or will -ever- need to know.

what they need to know:

air the tire up after you do the 70-90% fill, depending on whose chart you use, add air till the tire deflection and ground patch look good.. should be close to air pressure needed for an un ballasted tire, not counting loads on the tractor.. don't exceed tire or tube max pressure.

what they don't need to know:

ANY of the MATH about the compressibility of a fluid or liquid .

soundguy

Some of my best friends are hayseeds...I wouldn't trade their friendship or practicality for anything. They know more about ballasted tires than you or I could ever hope to.

 

[RickB]

No Rick...20 PSI is the recommended pressure on both the sidewall and in the owners manual.

I guess you have been too busy typing to read the good info in this thread about sidewall deflection vs. inflation.
Or you just don't want the facts to interrupt your dissertation.

Inflating rear tractor tires by the sidewall information is a rookie mistake. That info is seldom anything but a guidline to keep from damaging the carcass itself by overinflating it.

 

[Soundguy]

Some of my best friends are hayseeds...I wouldn't trade their friendship or practicality for anything. They know more about ballasted tires than you or I could ever hope to.

what kind of a response was that? a red herring diversion and then a slight about my intelegence level?

I know everything i need to know about my tractor tires inflation level when I walk around them in the am before i start working on the machine.. rarely do I ever pull out a gauge and never have i ran into the house for my slide rule.

i'm outta here... math minutia was bad enough.. insults now? later.. go argue with the wall.

oh wait.. one other thing I can think of to improve my happiness today (mouseclick) ahh.. that's better...

soundguy

 

[mustangsallysdad]

Everything under pressure increases its temperature. It is a fact that in a diesel engine the fuel is injected after the air is compressed (Diesel engine - Wikipedia, the free encyclopedia). That is how a diesel engine works.
A fluid does not reduce its volume under pressure i.e. it is non compressible. That is why a loaded tire needs air to prevent bursting.

Find a good book on Thermodynamics and check back after having read it thoroughly. It's much more complicated than that.

 

[RickB]

Some of my best friends are hayseeds...I wouldn't trade their friendship or practicality for anything. They know more about ballasted tires than you or I could ever hope to.

Don't include me in that. I AM a hayseed, and I do know more about ballasted tires than you. I've owned and operated farm tractors all my life doing work that required proper ballasting for efficiency.
I've also probably driven tractors in reverse farther than you ever will in a forward direction. But saying that would be rude and condescending, and I'm not like that.

 

[Soundguy]

my bad.. it's more like (mouseclick) (mouseclick) (mouseclick) (mouseclick) to add someone to an ignore list... not just the single (mouseclick) I indicated earlier

soundguy

 

[mustangsallysdad]

Don't include me in that. I AM a hayseed, and I do know more about ballasted tires than you. I've owned and operated farm tractors all my life doing work that required proper ballasting for efficiency.
I've also probably driven tractors in reverse farther than you ever will in a forward direction. But saying that would be rude and condescending, and I'm not like that.

No Rick...I believe in giving credit where credit is due...you are like that...and this wasn't my dissertation...that was "Aerodynamic Properties as Proven by Bernoulli's Principle". Mouseclick as well...outta here!

 

[mustangsallysdad]

what kind of a response was that? a red herring diversion and then a slight about my intelegence level?

I know everything i need to know about my tractor tires inflation level when I walk around them in the am before i start working on the machine.. rarely do I ever pull out a gauge and never have i ran into the house for my slide rule.

i'm outta here... math minutia was bad enough.. insults now? later.. go argue with the wall.

oh wait.. one other thing I can think of to improve my happiness today (mouseclick) ahh.. that's better...

soundguy

"intelegence"???

 

[SPYDERLK]

There are a few things to consider.
1] The compression ratio inside a filled tire is much greater and so the pressure will rise quickly as the tire deflects as it begins to bear more weight.
2] How varied are the weights of the implements used.
3] How varied are the amounts of tractive force that are required to pull the load?

Due these and other incidentals I run a range of pressures decided by how the tractor looks when configured for the job at hand. I want to see 2 bars touching to the edge on each side of the tire. This gives a little bulge that I consider no problem. What I dont want is to see is much sidewall crinkle next to the tread bars under consistent pull load conditions. Any significant crinkle beyond momentary is cause for more inflation pressure. Due to the higher compressional stiffness, and the fact that the fluid filled tire has 1 to 2 psi greater internal pressure at the bottom, I find that pressures can be run 2 or 3 psi lower. Depending on the job and tractor weight I will run anywhere from 5psi up. Fronts are often near their peak rated pressures. Rears almost never.
larry

 

[Aaron_D]

Wow... Hate to jump into this storm but... The compressibility of the ballast liquid has no affect on straying from your mfg recommended tire pressure. Yes liquids are not incompressible (nothing is) but due to their low compressibility they are often assumed to be so. Additionally the change in temperature changes the density vastly more than pressure and even if the density changed, the pressure is equal throughout.

In a standard automotive tire for every 10 degrees the pressure changes approximately 1 psi. As a tractor tire has way more volume, it should be more. Adding a liquid would reduce the volume of air changing the affect of density. As SPYDRLK stated, lowering the volume of air does slightly change the way your tire reacts to tire deflection by requiring the air to compress more per its volume making the ride more harsh. It doesn't change the internal pressures the tire see's though.

Keep the pressure the same. By that I mean that your pressures should reflect your usage and load at the time. There is no 1 perfect tire pressure. The mfg recommended pressure is the starting point (general one size fits all) but usage dictates the proper pressure for your need. Just don't exceed the max pressure rating on the tire.

 

[The Haymaker]

Man, am I doing things the hard way. On my loaded tires, I inflate them until two criteria are met.

1) The tire is not flat on one side.

2) The tractor does not lean at more than a 45 degree angle left or right.

Is this killing my mpg?

 

[SPYDERLK]

As SPYDRLK stated, lowering the volume of air does slightly change the way your tire reacts to tire deflection by requiring the air to compress more per its volume making the ride more harsh. It doesn't change the internal pressures the tire see's though.

Keep the pressure the same. By that I mean that your pressures should reflect your usage and load at the time. There is no 1 perfect tire pressure. The mfg recommended pressure is the starting point (general one size fits all) but usage dictates the proper pressure for your need. Just don't exceed the max pressure rating on the tire.

Sure it does. Beyond the static inflation condition, equal additional deflection in a filled vs unfilled tire will cause a higher pressure in the filled tire. This prevents the filled tire flattening as much as the unfilled under equal load. For this reason you can run the filled tire softer in general, giving a good ride and still not too much squat under heavier loads.
larry