5425 vs 4320 vs 3720 Surface Pressure

[LD1]

So its all about effective contact surface area as opposed to psi alone to determine the surface pressure.

So unless I doubled my contact surface area when reducing my pressure in half, in real life, I probably only reduce the surface pressure by 5-15%, depending on lug type and sidewall stiffness.

That makes a lot more sense!

Correct:thumbsup:

If you go to a machine twice as heavy, but the same tire pressure, you need to have TWICE the ground contact area to have the same PSI.

Another example...My L3400 weighs 2600lbs BARE. Tires are 30PSI front and 12 psi rear.

Same tractor Just add a loader and a bushhog.
Tractor...................2600
Heavy bushhog.......1100
FEL and bucket........1300

Almost double the weight and still the tire PSI is the same. Which combo do you think is going to make bigger/deeper ruts if it is soft???? Cause the tires certainly arent going to "squish" out to 2x's the contact they were before.

And think about duels on tractors. or even a p/u for that matter. A second tire the same size and at the same PSI as before. Using the logic of (ground pressure = tire psi), wouldnt adding a second tire DOUBLE the ground pressure:confused2: And to think them stupid old farmers were running duels so they didnt compact the soil as much. Little did they know that they were compacting it twice as much:laughing:

 

[buickanddeere]

Actually keeping 10psi in the tires and doubling the weight each tire is carrying will double the contact area with the ground. Just eyeballing the tire sitting in dirt doesn't show everything that is happening. Roll the tire onto polycarbonate then watch the contact patch increase or decrease as psi and/or weight is varied.

 

[LD1]

Actually keeping 10psi in the tires and doubling the weight each tire is carrying will double the contact area with the ground. Just eyeballing the tire sitting in dirt doesn't show everything that is happening. Roll the tire onto polycarbonate then watch the contact patch increase or decrease as psi and/or weight is varied.

If you really believe that.......then explain to me why when I take the loader and bushhog off my tractor in soft conditions, it doesnt rut things up half as bad as when they are on?????

I sure you may come up with some lengthy and crazy explanation, but even if you do...it really doesnt matter. Because here on TBN, when we refer to ground pressure, we are talking about how much the soil gets compacted and/or rutted. And for that....Tire psi dont mean squat.

 

[jenkinsph]

LD1,
In your muddy scenario the soft ground can not support the 10 psi or 30 psi contact without diflection. This causes the tire to sink to terra firma until it has enough resistance meet the load bearing on it.

 

[LD1]

LD1,
In your muddy scenario the soft ground can not support the 10 psi or 30 psi contact without diflection. This causes the tire to sink to terra firma until it has enough resistance meet the load bearing on it.

Thats not my point.

My point is the soft ground CAN support my 10 and 30 psi tires MUCH better when the tractor weighs 2600 lbs. Throw on my bushhog and FEL and double its weight.......and it dont support it worth a hoot.

Call it what you want, I dont care. But for the application that 99% of TBN'ers are askign about this for.....tire pressure dont matter. Questions like "what tractor will rut my lawn worse"? And using my above example......If I take my Tractor with loader and bushhog and lower the pressures, it is still going to make a rutted up mess. Likewise, I could UP the pressure of the bare tractor, and still not make nearly the mess.

 

[morrisond]

So as the starter of the post, thank you for the enlightening discussion.

My Question still stands.

If I put the appropriate sized R3 Tires on my 5425 will it be as easy on the lawn as a 3720 with R3's?

 

[jenkinsph]

So the question is the 5425 weighs over 7000lbs but it has larger tires. The smaller tractors are 3-4000 Lbs.

How big a difference in surface pressure with Turf Tires on all 3 is there?

.

LD1,
This was the original question the OP was asking. The surface pressure is directly related to the tires pressure.

Whether the ground is too soft to mow without rutting or whether he should wait a day or two to mow the lawn isn't what we were asked. I would hope that a guy with a 5425 and a 1600 WAM has had some experience and judgement to know when to mow and when to wait.

 

[murphy1244]

So instead of using a dually, I just let some air out of the tires?

 

[LD1]

LD1,
This was the original question the OP was asking. The surface pressure is directly related to the tires pressure.

Whether the ground is too soft to mow without rutting or whether he should wait a day or two to mow the lawn isn't what we were asked. I would hope that a guy with a 5425 and a 1600 WAM has had some experience and judgement to know when to mow and when to wait.

I know what the OP was asking. Thats why I answered him the way I did. Because what you "believe" is that it dont matter what size the tire is, ground pressure is the same as tire PSI. And that is simply incorrect. If the tire were like a balloon, yes. But tires arent. They have sidewalls and belts. This keeps them from making drastic changes as the pressure changes. IE: doubling the tire pressure doesnt double its size. Therefore, while tire PSI does have an effect on ground pressure, it is far from linear.

You would have the OP believe that if he were to take the smaller tires off of the 3720, and put them on the 5425, as long as PSI is the same, ground pressure would be the same, or vice versa with the large tires on the small tractor, but they are not the same. Duallys ring a bell?? Are you saying that two dual tires @ 30PSI have just as much ground pressure as 1 @ 30PSI???

So instead of using a dually, I just let some air out of the tires?

:thumbsup::laughing:

 

[jenkinsph]

So as the starter of the post, thank you for the enlightening discussion.

My Question still stands.

If I put the appropriate sized R3 Tires on my 5425 will it be as easy on the lawn as a 3720 with R3's?

Yes, but as mentioned above the ground needs to be firm enough to support any of the tractors without making a mess.

For my lawn work I use an x749 with 26 12 12 hdap tires and 8psi to lower the ground pressure this will be much easier on the lawn than my larger tractors with cleats and 12psi tire presssure on the rear and 25 psi in the fronts.

Yesterday a friend of mine was aerating/coring one of the local golf courses witha 5325 with R3 tires, didn't appear to be making a mess of anything either.