Ballast rim guard and proper inflation

[Billrog]

I can really agree that volume doesn't matter because you are compressing the molecules.
Pressure and volume are inversely proportional to
each other. This means that as the pressure
decreases, the volume increases, and as the pressure
increases, the volume decreases. One way to think
of this is if you push on a gas by decreasing its
volume, it pushes back by increasing its pressure.
Interested in more comments.

 

[ovrszd]

Yeah, I also am interested in different perspectives and comments. I'll go away from this discussion with more knowledge.

S219 came closest to touching my mental capacity with his description.

I'm still trying to fully understand how that Big A tire can carry 10K on 3psi while my truck tire can't carry 1.7K on the same 3psi. His theory of contact patch size makes sense to me. Just gotta get it chewed down so I can digest it.

 

[jonsstihl]

its all about psi pounds per square inch. think of why people wear snow shoes so they don't sink in the snow or a 100 pound woman having trouble walking on grass in high heels when the five hundred pound woman in sneakers has no trouble.

a one square inch contact patch would need a hundred psi to lift a hundred pounds but a ten square inch contact patch would only need 10 psi to do it. look at the size of those tires on the A. they must have atleast four times the contact patch of a truck tire.

 

[murphy1244]

Yeah, I also am interested in different perspectives and comments. I'll go away from this discussion with more knowledge.

S219 came closest to touching my mental capacity with his description.

I'm still trying to fully understand how that Big A tire can carry 10K on 3psi while my truck tire can't carry 1.7K on the same 3psi. His theory of contact patch size makes sense to me. Just gotta get it chewed down so I can digest it.

Do you really know that only 3psi is in that tire? Not being a smarty Richard.

 

[ovrszd]

its all about psi pounds per square inch. think of why people wear snow shoes so they don't sink in the snow or a 100 pound woman having trouble walking on grass in high heels when the five hundred pound woman in sneakers has no trouble.

a one square inch contact patch would need a hundred psi to lift a hundred pounds but a ten square inch contact patch would only need 10 psi to do it. look at the size of those tires on the A. they must have atleast four times the contact patch of a truck tire.

Yep, totally agree. That was S219's point as well. The Big A tire probably has 20 times the contact patch size as my truck tire.

It appears my truck tire has a contact patch of 90.25 Square Inches. I don't have access to the Big A for verification of it's contact patch. Maybe someone can measure their tractor tires? Mine are all at the farm in the machine shed.

 

[dadster4]

Wrong. Air compresses and an inflated tire contains a significantly higher volume of air. If it was filled with compressed water you would be closer to right, but still wrong because the pressurized tire expanded.

Not wrong...the volume will remain the same, or nearly so, but the pressure will increase. A tire with a large volume will have more surface area inside the tire to exert each psi upon, so...the Big A (huge tires with massive amount of surface area) can support a load with very little internal pressure, while a small tire (think front tractor tire) requires a higher pressure acting upon a smaller surface area to support the load it carries.

 

[ovrszd]

Not wrong...the volume will remain the same, or nearly so, but the pressure will increase. A tire with a large volume will have more surface area inside the tire to exert each psi upon, so...the Big A (huge tires with massive amount of surface area) can support a load with very little internal pressure, while a small tire (think front tractor tire) requires a higher pressure acting upon a smaller surface area to support the load it carries.

I can understand this.

This plays into my very first statement about this subject. I said it's the volume of atmospheric pressure air in the tire that carries the load versus the PSI. My statement, not being technically written, confused most that read it.

Your statement is saying the same thing I did, just in a more logical, acceptable way.

 

[TomNOh]

Maybe this will help, maybe not. If that Big A used a dual tire setup with the total volume of the 2 tires equaling the volume of the single tire, it would be able to carry the same load with even less pressure because the 2 tires would have more square inches of surface area than the single tire. Also, it is the TOTAL of ALL of the square inches of INTERIOR surface area of the tire, NOT just the contact patch. The air pressure is pushing on all interior surfaces of the tire & rim equally.

 

[rd_macgregor]

Ideal Gas Law (FWIW): PV=nRT
In the real world, having memorized this formula in college nearly 50 years ago, it has never been of practical use to me. For me, the biggest issue has been that I'm never working in a closed system, so T is able to equilibrate with the ambient.

A more useful reformulation might be P1V1/T1=P2V2/T2 where you can re-sort the variables to isolate the one you want to calculate ("unkown").

Looking into this thread, I was interested in the impact on tire performance, load capacity, and necessary pressure in a filled tire. Since the fill fluid is essentially uncompressible, then the small remaining air volume's pressure is transmitted throughout the tire, and all the discussion above about footprint and internal pressure still holds true, right? That is, I don't need to air up a filled tire any differently than an unfilled tire...it will just take fewer moles (ie, X times 6.023 x 10- 23rd molecules)of air to get the pressure up to, say, 15psi in the filled tire.

 

[Texasmark]

I am most concerned about how the tire sits on the ground. PSI is only for comparison.

Now here's where these "air" discussions sometimes take a left turn.

The cubic feet of atmospheric pressure air that's in your tire is what determines how much load it will carry at a particular stance. That's why my 6800lb truck runs 50 psi in it's 305/70/16 tire. And that's why my 10000lb tractor runs 20 psi in it's 18.4x30 filled tire. That's also why a Big A can carry 10000 lbs of load in the bed on three tires running 2-3 psi. Cubic feet of air not pressure carries the load.

View attachment 490365

Force is square inches x #/ inch squared. Same formula as a hydraulic cylinder force acting on a log splitter or what have you.
You have many square inches so it only takes a few # to support/equal the opposing force....the unit.