5425 vs 4320 vs 3720 Surface Pressure

[LD1]

So let's try this again.

Imagine the tire is a boloney skin for simplicity. Inflate it to 10 psi. That means every square inch of tire has 10 pounds pushing on it.

Put on the tractor, and set the machine on the ground. Every square inch of tire still has 10 pounds pushing on it. That includes the tire that is in contact with the ground.

The tire will deform until the tractor is supported and every square inch of tire has 10 pounds pushing on it. The total weight per tire will be proportional to the weight of the tractor and the weight distribution front to rear, side to side. The pounds per square inch of contact remains the same.

You can't go to zero because the tire is no longer supporting the tractor and you get a divide by zero error

The tread pattern is going to affect behaviour which is why the R1's sink in until the casing hits the ground. The R3 is the closest to a boloney skin and causes the least amount of damage.

R1's cause more soil compaction on the larger tractor because the bar sinks in with higher pressure until the contact patch levels out and the pressure is distributed.

Still not true. A tire is belted and has sidewalls. If a tire were like a balloon, then yes, I would agree with your logic. But it is not. Even your turf tires, and even if you are on concrete, doubling the load will NOT double the contact patch (which it would have to in order for your "theory" to hold up). Likewise, cutting the air pressure in half does NOT double it either.

Changing the load or air pressure does INDEED change the contact patch. BUT they are NOT linear.

 

[Piston]

What are you possibly talking about ? Who is driving around without valve cores in the stems? Driving on rims and floating tractors? Are you daft? Why are you avoiding the issue and physics then running off with some complete and total falsehood as if it's truth?

Reread my post....

Okay so take the valve stem out and operate like that. Or better yet, take the tire off completely and run the tractor on the rim. Walah, back to the magical floating tractor.

Like I said, that's the way it sounds, however to be fair (I'm just having fun ) I'm sure there is some sort of good physics explanation that has something to do with the correlation. But I'll admit I don't know either.

As mentioned, the best thing to do is get high flotation tires to ensure the least disturbance. May also invest in a turf aerator for aerating once a year and your all set.

 

[charleyfarmall]

Oh man, LD1, did you let Boeing know?

 

[LD1]

Oh man, LD1, did you let Boeing know?

On my list of things to do today:thumbsup:

In all seriousness though, aircraft tires are about the closest to a balloon as you could get. So I am sure the ground pressure is much closer to PSI on them. Since they are like a balloon and on hard surfaces only.

Car tires, tractor tires, etc are different. Ground pressure and PSI are NOT LINEAR.

So, I will call boeing engineers if you call EVERY big farmer and tell them that they are wasting time an money running duals since ground pressure is =to tire PSI, and that running 4 tires @ 8 psi is TWICE the compaction as 2 tires @ 8PSI

 

[charleyfarmall]

You are right, it's not 1:1, but within a range of pressure it is actually linear. Tire construction does matter, and they are designed to operate within a narrow range of pressure.

The reason for larger tires, duals and triples is because the soil conditions will not tolerate the pressure, say 10psi in this case. You can certainly decrease contact pressure by going way up in tire volume.

 

[jenkinsph]

On my list of things to do today:thumbsup:

In all seriousness though, aircraft tires are about the closest to a balloon as you could get. So I am sure the ground pressure is much closer to PSI on them. Since they are like a balloon and on hard surfaces only.

Car tires, tractor tires, etc are different. Ground pressure and PSI are NOT LINEAR.

So, I will call boeing engineers if you call EVERY big farmer and tell them that they are wasting time an money running duals since ground pressure is =to tire PSI, and that running 4 tires @ 8 psi is TWICE the compaction as 2 tires @ 8PSI

LD1,
How many airplane tires have you dealt with? All I have seen were very high ply count. Those 747 tires with 32 plys should be super flexible NOT.

 

[LD1]

LD1,
How many airplane tires have you dealt with? All I have seen were very high ply count. Those 747 tires with 32 plys should be super flexible NOT.

I was refering to the shape of them. They are more rounded. Kinda like a motorcycle tire. They arent like a passenger car tire or a turf tire on a tractor that has a definitive sidewall and a flat contact area.

 

[jenkinsph]

I was refering to the shape of them. They are more rounded. Kinda like a motorcycle tire. They arent like a passenger car tire or a turf tire on a tractor that has a definitive sidewall and a flat contact area.

The key point that most of us have been trying to make to you is that within the design parameters of a given tire the tire pressure is a close match to ground pressure. If you exceed the design pressure or deflate the tire beyond the design limits you can distort the tire and all bets are off.

The OP asked about R3 tires on three different tractors no one but you has said anything about using the same size tire on the different sized machines. The 5425 will use physically larger R3 tires than a 3x20 or 4x20 tractor which weighs much less. I think most of us understood that appropriate R3 tires would be selected for each of the tractors being considered.

This isn't rocket science, just simple physics. Your repeated comments about dual tires:confused2: have no idea where you are going with that.

 

[ctlguy]

On my list of things to do today:thumbsup:

In all seriousness though, aircraft tires are about the closest to a balloon as you could get. So I am sure the ground pressure is much closer to PSI on them. Since they are like a balloon and on hard surfaces only.

Car tires, tractor tires, etc are different. Ground pressure and PSI are NOT LINEAR.

So, I will call boeing engineers if you call EVERY big farmer and tell them that they are wasting time an money running duals since ground pressure is =to tire PSI, and that running 4 tires @ 8 psi is TWICE the compaction as 2 tires @ 8PSI

Running duals, etc on Ag machines. Ground pressure is only a part of the reason. Adjusting tire pressure, dualls, etc is to control hp to the ground. Issues like power hop, slippage, and stability all come into play as to why one would run dualls. If it was only ground pressure there would be a lot more track units out there. (that is a whole nutter discussion on the tradeoff for compaction vs burming, soil conditions, application, etc.) Sorry was avoiding this post, but it got interesting, had to put my 2 cents in for whatever it is worth !!

 

[LD1]

The point that I am trying to make is that THIS

The key point that most of us have been trying to make to you is that within the design parameters of a given tire the tire pressure is a close match to ground pressure.

Simply isnt true.

There may be a SINGULAR point at which PSI = Ground pressure. But any pressure or load change changes all of that.

My front tires @ 30PSI have LESS ground pressure with the loader OFF than they do with the loader on. As VERY evident by driving across a lawn both ways.

Same thing with the rears and the bushhog on vs bushhog off.

I think at this point, we have all said our piece and well just have to agree to disagree on this one.