Loaded tire pressure

[sevilla]

Hi, I have a Kubota L3830 with loaded real industrial tires. I need to inflate the rear tires but I have a few questions. The manual states that the tires should be inflated at 20PSI but does not specify if loaded or not. Which is the correct pressure in your experience? Also, for loaded tires any compressor will do? Since I do not have one any recommendation for a reliable one?
Thank you so much.

 

[mustangsallysdad]

Hi, I have a Kubota L3830 with loaded real industrial tires. I need to inflate the rear tires but I have a few questions. The manual states that the tires should be inflated at 20PSI but does not specify if loaded or not. Which is the correct pressure in your experience? Also, for loaded tires any compressor will do? Since I do not have one any recommendation for a reliable one?
Thank you so much.

I've personally found that about 10 PSI will absorb the shock on my loaded tires and still provide an acceptable ride and load capability...they also have a 20 PSI sidewall rating...might want to look into a tire gauge made for liquid filled tires (TSC).

 

[atgreene]

Pressure is the same whether loaded or unloaded.

It has been my experience that if you are going to put air in calcium filled tires you should rotate the tire valve to near the top. I put a small amount of air in the valve stem to prevent any calcium from coming back into the valve, then use an air guage to check pressure. If you do get some calcium "spittle" back through the valve and into your air guage, clean it good and oil it lightly to prevent rusting/corrosion.

 

[skipmarcy]

As said - air pressure is the same whether loaded or not. I too like to run about 10 psi in mine, better traction & ride both. Mine are loaded with methanol and I use a spring-loaded tractor tire gauge.

 

[sevilla]

Thanks for the informations.

 

[Mace Canute]

From Installing Liquid Ballast in Tires | Gempler's
"Tires are designed to operate at maximum efficiency when they are at their Rated Deflection. With the tractor on a hard surface, deflection is the distance from the axle center to the ground surface divided by the distance from the axle center to the top of the tire. In technical terms, deflection is the value of the loaded radius of the tire compared to the unloaded radius. Rated deflection is the amount of deflection when the tire is deformed to its optimum or design footprint. Rated deflection for radial tires is about 85%, for bias tires it is about 90%. The correct pressure to achieve rated deflection depends on the load the tire is carrying. A correctly inflated radial tire will have a significant sidewall bulge or "cheek'. It may look low or flat but it is not. If you inflate a radial tire by "eyeball" until the sidewall bulge looks like that of a bias ply tire, you lose most of the performance advantages of the radial tire.

The tire gauge you use and the way you use it can have a big effect on what you think the tire pressure is. Always start with a good gauge, one that costs money, is easy to read, and is graduated in 1 psi increments. If your gauge cost 99 cents or came free from a feed dealer, has marks every 5 psi from 0 to 100 psi, and looks like it will break if you drop it, you are probably not going to measure pressures accurately.

Ideally, tire pressures should be measured in the morning, cold, or when the the tractor has not been used for several hours. As a tractor is used and the tires warm up, tire pressures will increase from 1 to 3 psi.

If tires have fluid ballast in them, the pressures at the bottom of the tire can be as much as 1.5 psi higher than at the top, depending on the amount of ballast. Whether you measure at the top or the bottom doesn't matter as much as whether you are consistent in where you measure. It is less messy if you measure with the valve stem at the top but it may be slightly more accurate if you measure with the valve stem at the bottom."

For anybody contemplating filling their own tires for the first time, this site gives some good step by step instructions with pics Installing Liquid Ballast in Tires | Gempler's

There is quite a bit of good information in this site Installing Liquid Ballast in Tires | Gempler's and this site http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/eng9920

 

[Soundguy]

yep.. psi is psi.. load then fill with air to correct psi as per the manual / dealer /manufacturer specs.. etc.

soundguy

 

[mustangsallysdad]

yep.. psi is psi.. load then fill with air to correct psi as per the manual / dealer /manufacturer specs.. etc.

soundguy

Come on guys! Think about it. It's true...PSI is PSI, however, liquid compresses at a much higher pressure than air...if you add liquid ballast to a tire, you have essentially added material to the tire (decreased the internal volume) and you will find that maintaining the sidewall rated PSI on a loaded tire is going to be a pain in the butt! Literally. Much rougher ride quality. But, it's your butt, not mine!!! LOL.

 

[RickB]

The info about sidewall deflection is priceless, and not often discussed here. Inflate your tires so as to achieve the recommended amount of deflection. That will be dependent on tire construction and axle loading. You can't read that from a book or sidewall, as axle loading is a variable. Most R-4 tires on CUT's are grossly overinflated relative to the load they carry and the contact patch they SHOULD be making.
Using liquid ballast is a tradeoff of convenience and dollars against traction, compaction, and ride. Convenience and dollars win 85% of the time.

 

[Big Bri]

Come on guys! Think about it. It's true...PSI is PSI, however, liquid compresses at a much higher pressure than air...if you add liquid ballast to a tire, you have essentially added material to the tire (decreased the internal volume) and you will find that maintaining the sidewall rated PSI on a loaded tire is going to be a pain in the butt! Literally. Much rougher ride quality. But, it's your butt, not mine!!! LOL.

i dont think that most liquids could be compressed, at least the ones we use in our tires, so if you put 20 psi in your liquid filled tire then you would have 20 psi in the tire.

 

[Soundguy]

that is correct.

soundguy

(edit)

PS.. folks reading this thread might look at this thread.. note the deflection comments about the tire that rick brings up. it really is an easier way to determine correct tire pressure than carrying a tire gauge in your shirt pocket.

http://www.tractorbynet.com/forums/owning-operating/164684-yet-another-tire-pressure-question.html

soundguy

 

[mustangsallysdad]

i dont think that most liquids could be compressed, at least the ones we use in our tires, so if you put 20 psi in your liquid filled tire then you would have 20 psi in the tire.

Re-read my post...liquid compresses at a much higher pressure than air...adding liquid ballast in your tire essentially decreases the internal volume of the tire as the liquid is not going to compess at a typical tire pressure...it's sort of like you have decreased the size of the tire...if you re-inflate to sidewall PSI or whatever pressure you were running prior to the liquid fill, the tire will not provide as much sidewall deflection as you have now (in theory) overinflated the tire. It will ride much harder. I know based on my personal experience in examining the sidewall deflection before and after fill (fronts only, I was only concerned about loader use) and have settled in on around 10 PSI on the rears and about 12-14 PSI on the fronts. At least that's what my butt and full loader bucket tell me. And as far as liquids being compressed; even mercury can be compressed.

 

[Soundguy]

Mustang...The pressure is the same filled or not...period.

The ride is harder because you have more weight and less air doing the cushoning.

the tire deflection is a lil different because you have more weight on the wet tire vs an air filled tire.

take a tractor with air in its rears and one with ballast in them.. the ballasted one weighs more. if you run equal air pressure in both, the ballasted tires squat more because there is more weight on them.

figure the ballasted difference in weight and then add rear axle weights to that tractor with air in it's tires and I bet you will find the tires squat nearly identically.

considering a 13.6x28 tire ballasted with only water adds a whopping 359# per side, not counting ballast material like cacl.. or a heavier liquid like rimguard, that means you are adding a MINIMUM of 718# to that tractor rear... OF COURSE the tires are going to deflect and squat more than the otherwise equal tractor setting next to it at the same psi that weighs 718# less.

That's why it was brought up that you need to compair tire deflection and air pressures with whatever load you normally have on your tractor when you decide if you have enough inflation or not, looking at tire deflection and ground contact patch.

no magic in loaded tires.. just physics... and you need to compair equally weighted machines to compair the sidewall deflection.

soundguy

 

[RickB]

Re-read my post...liquid compresses at a much higher pressure than air...adding liquid ballast in your tire essentially decreases the internal volume of the tire as the liquid is not going to compess at a typical tire pressure...it's sort of like you have decreased the size of the tire...if you re-inflate to sidewall PSI or whatever pressure you were running prior to the liquid fill, the tire will not provide as much sidewall deflection as you have now (in theory) overinflated the tire. It will ride much harder. I know based on my personal experience in examining the sidewall deflection before and after fill (fronts only, I was only concerned about loader use) and have settled in on around 10 PSI on the rears and about 12-14 PSI on the fronts. At least that's what my butt and full loader bucket tell me. And as far as liquids being compressed; even mercury can be compressed.

We won't be able to prove this one way or another, but I'll bet that you cannot tell whether a particular tractor's rear tires are liquid filled or not by the ride characteristics alone.

The only point I will concede to you is that as the volume of liquid ballast within a tire increases, the volume of compressible fluid (air) decreases.

Elevating (or lowering) the level of discussion here to debating the actual amount a given liquid can be compressed removes the discussion so far from the real world we started in that the thread becomes meaningless. Nobody cares how much that water, or even mercury can be compressed. In my world neither do to a degree that I care about.

 

[mustangsallysdad]

Mustang...The pressure is the same filled or not...period.

The ride is harder because you have more weight and less air doing the cushoning.

the tire deflection is a lil different because you have more weight on the wet tire vs an air filled tire.

take a tractor with air in its rears and one with ballast in them.. the ballasted one weighs more. if you run equal air pressure in both, the ballasted tires squat more because there is more weight on them.

figure the ballasted difference in weight and then add rear axle weights to that tractor with air in it's tires and I bet you will find the tires squat nearly identically.

considering a 13.6x28 tire ballasted with only water adds a whopping 359# per side, not counting ballast material like cacl.. or a heavier liquid like rimguard, that means you are adding a MINIMUM of 718# to that tractor rear... OF COURSE the tires are going to deflect and squat more than the otherwise equal tractor setting next to it at the same psi that weighs 718# less.

That's why it was brought up that you need to compair tire deflection and air pressures with whatever load you normally have on your tractor when you decide if you have enough inflation or not, looking at tire deflection and ground contact patch.

no magic in loaded tires.. just physics... and you need to compair equally weighted machines to compair the sidewall deflection.

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). 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. 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.

 

[sevilla]

I'm a little confused. In my middle grade classes I was thought that liquids were, for practical purposes, incompressible.

 

[mustangsallysdad]

We won't be able to prove this one way or another, but I'll bet that you cannot tell whether a particular tractor's rear tires are liquid filled or not by the ride characteristics alone.

The only point I will concede to you is that as the volume of liquid ballast within a tire increases, the volume of compressible fluid (air) decreases.

Elevating (or lowering) the level of discussion here to debating the actual amount a given liquid can be compressed removes the discussion so far from the real world we started in that the thread becomes meaningless. Nobody cares how much that water, or even mercury can be compressed. In my world neither do to a degree that I care about.

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.

 

[mustangsallysdad]

I'm a little confused. In my middle grade classes I was thought that liquids were, for practical purposes, incompressible.

Ever been scuba diving?

 

[sevilla]

No, I have not.

 

[mustangsallysdad]

No, I have not.

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.