Ground PSI

[TimberXX]

I have a very soggy lot. I'm trying to figure out the machines with the least amount of ground pressure. I have an acre of grass. I am considering an x350, x380 and a x570. I was assuming 60/40 split of the weight of the machines before accounting for the operator, but I'm not sure if that's right. Does deere have published numbers of ground pressure?

 

[3Ts]

I've never seen it for JD tractors. It's going to depend on the tires and their inflation pressure so I'd be surprised if it exists. If you can find out the footprint of the tires, you can calculate the ground pressure.

 

[TimberXX]

I've never seen it for JD tractors. It's going to depend on the tires and their inflation pressure so I'd be surprised if it exists. If you can find out the footprint of the tires, you can calculate the ground pressure.

I am using the equation of Weight/(Tire Radius*Tire Width), but the assumption of the weight distrubtuion between axles is a big one.

For Example, I had a Scag patriot ZTR. 950 lbs, and it destroyed my lawn. But with a ZTR, the transmissions, operator, and engines are all essentially on the rear axle.

Thanks in Advance for Any Help!

 

[s219]

For a traditional tire that is inflated enough to be in the proper operating range, with smooth-ish tread (ie, not aggressive bar or lug tires), the ground pressure will always be within a couple % of the inflation pressure (many times it will match almost exactly). So if you want to minimize the ground pressure, look for the mower that specs the lowest PSI inflation pressure for the tires. It's that simple. Even if you don't do an exact calculation and just want to find the best mower for soft ground, look for the one with the lowest PSI inflation specs for the tires.

We can prove this with a fairly routine physics derivation or very basic experiment, but it's become enough of an engineering rule of thumb that I think you can just run with it. This rule of thumb breaks with run-flat tires or tires with sidewalls stiff enough to support weight at zero inflation pressure. It only works on tires that require air pressure to support weight. It also breaks with tires that have aggressive tread. A mower turf tire is on the opposite extreme, and fits the model pretty well.

 

[ArlyA]

s29 has that right but you could also get new wheels with wider tires as well. At least if you don't mind the extra expense. But if you get to wide, you'd be rubbing on the inside of your machine anyway. I have a 6x6 what totes around .6 psi :laughing: (with its tracks on)

 

[5030]

Don't load your tires. Simple answer.

 

[ruffdog]

I am using the equation of Weight/(Tire Radius*Tire Width), but the assumption of the weight distrubtuion between axles is a big one.

For Example, I had a Scag patriot ZTR. 950 lbs, and it destroyed my lawn. But with a ZTR, the transmissions, operator, and engines are all essentially on the rear axle.

Thanks in Advance for Any Help!

With adverse conditions, the amount the tires scrub the surface will make a difference too. A all wheel steer unit like my wifes x744 is much easier on the turf that a 2 wheel steer. It helps when all the wheels are helping turn than just two.

 

[TimberXX]

For a traditional tire that is inflated enough to be in the proper operating range, with smooth-ish tread (ie, not aggressive bar or lug tires), the ground pressure will always be within a couple % of the inflation pressure (many times it will match almost exactly). So if you want to minimize the ground pressure, look for the mower that specs the lowest PSI inflation pressure for the tires. It's that simple. Even if you don't do an exact calculation and just want to find the best mower for soft ground, look for the one with the lowest PSI inflation specs for the tires.

We can prove this with a fairly routine physics derivation or very basic experiment, but it's become enough of an engineering rule of thumb that I think you can just run with it. This rule of thumb breaks with run-flat tires or tires with sidewalls stiff enough to support weight at zero inflation pressure. It only works on tires that require air pressure to support weight. It also breaks with tires that have aggressive tread. A mower turf tire is on the opposite extreme, and fits the model pretty well.

Many of these tires have a pressure of 22 psi, but that seems two high for a ground pressure. Am I missing something.

 

[ArlyA]

Many of these tires have a pressure of 22 psi, but that seems two high for a ground pressure. Am I missing something.

That must be "maximum" pressure which you might not want to go that high.. Think of it like this; the more pressure is in the tire, the more firm the tire becomes and less of it needs to be touching the ground. Larger tires require less PSI to hold the same weight up and that's why I suggested looking at a larger wheel/tire size. (might not be practical anyway) Hope that helps.

 

[tomplum]

I wouldn't think there would be an appreciable difference in the machines you are looking at. The 500 series is much the same set up as the 300 sans the upgrade on the transmission, thicker transmission belt set up, battery etc. What does the weight in the specs say? Add a bigger deck, you add more weight. Tire pressure 10 / 14 is typical. That being said, I know a guy who had to pick up a cheapo MTD as his big Kubota Z sank in parts of his lot until the end of May.