Air pressure

mikeboggess

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I am confused on the air pressure needed in my rear tires. L2800 Kubota has 11.2 x 24 Firestone tires. Kubota says 14 psi, Firestone says 26 psi max air pressure. I frequently fill the bucket with dirt and rock. So . . . what air pressure should I use?
 

old and tired

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What do you keep the front tires set at? I would worry more about them if you are filling the bucket up

I would use what's written on the tractor tire... in my case 25 PSI on the rear tires and 35 psi on front. I have R4 / Industrial tires so my sizes are:

Industrial front: 27x8.50-15
Industrial rear: 15-19.5R4
 

JimDeL

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Go with Kubota's spec.
Just because the tire manufacturer lists the MAX inflation on the sidewall, it doesn't mean you should inflate to that.
 
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85Hokie

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As others have said - the tire manu is telling HOW much max - Kubota is telling what should be with a little sag and better grip.

The front end is far more important for loader work.
 
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North Idaho Wolfman

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Don't go by any paper written specs.
Go by what's written on the side wall of the tire.
It can vary greatly of book info.
You will not hurt a tire running it at max PSI, you will hurt a tire running it under and over loading it.
 
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GeoHorn

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Never thought this would happen…. Never thought it possible…that I’d criticize NIW’s advice on anything mechanical or tractor-wise…. but that advice he offered is not correct.

The pressures moulded into the sidewalls of a tire are the TIRE mfr’s maximum pressure for the max-load that tire is rated-for…. NOT what load you are asking that tire to carry on Your vehicle or in this case, tractor.

That writing on the tire sidewall has no bearing on the weight of the vehicle (in this case a tractor) versus the correct tire pressure to obtain best tread-contact/footprint/traction with that tire on That particular machine.

Go with Kubota’s printed advice on tire pressures. Same thing with your car, truck, trailer, airplane, etc.
 
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North Idaho Wolfman

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Never thought this would happen…. Never thought it possible…that I’d criticize NIW’s advice on anything mechanical or tractor-wise…. but that advice he offered is not correct.

The pressures moulded into the sidewalls of a tire are the TIRE mfr’s maximum pressure for the max-load that tire is rated-for…. NOT what load you are asking that tire to carry on Your vehicle or in this case, tractor.

That writing on the tire sidewall has no bearing on the weight of the vehicle (in this case a tractor) versus the correct tire pressure to obtain best tread-contact/footprint/traction with that tire on That particular machine.

Go with Kubota’s printed advice on tire pressures. Same thing with your car, truck, trailer, airplane, etc.
Wow, really...
Do you run air planes tires randomly under inflated?
Do you run you car/truck tires randomly under inflated?
Remind me to never ride with you!

MAX tire pressure should never be chosen off of a book, as that info could be completely WRONG and could get you hurt.
The tire pressures listed on the side of a tire means that tire will perform and hold that pressure SAFELY per the manufacture of that tire, not some random figure that someone thinks up at random.
If you also note along with the pressure listing will also note a weight rating for that tire.
So you should take that into account.
Less pressure in a tire does NOT equate out to a higher weight load rating but a LOWER weight load rating and possibly tire damage due to under inflation!
 
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jyoutz

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Wow, really...
Do you run air planes tires randomly under inflated?
Do you run you car/truck tires randomly under inflated?
Remind me to never ride with you!

MAX tire pressure should never be chosen off of a book, as that info could be completely WRONG and could get you hurt.
The tire pressures listed on the side of a tire means that tire will perform and hold that pressure SAFELY per the manufacture of that tire, not some random figure that someone thinks up at random.
If you also note along with the pressure listing will also note a weight rating for that tire.
So you should take that into account.
Less pressure in a tire does NOT equate out to a higher weight load rating but a LOWER weight load rating and possibly tire damage due to under inflation!
I have truck tires on my 3/4 ton truck. The tires have a max pressure of 80 pounds. The truck handles terrible and bounces with 80 pounds, but very nice at 60 pounds pressure. The tire dealer said to run 60 unless hauling a lot of weight, then run 80. Different tire pressures are appropriate for different uses on the same machine
 
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North Idaho Wolfman

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I have truck tires on my 3/4 ton truck. The tires have a max pressure of 80 pounds. The truck handles terrible and bounces with 80 pounds, but very nice at 60 pounds pressure. The tire dealer said to run 60 unless hauling a lot of weight, then run 80. Different tire pressures are appropriate for different uses on the same machine
I agree, but you wouldn't use a book to tell you what max pressure should be would you?
 

jyoutz

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I agree, but you wouldn't use a book to tell you what max pressure should be would you?
Nope. Unless the tires are OEM. I would think the manufacturer would provide correct tire pressure for the tires they sell on the machine. Kinda like the pressure specs on the door panels of vehicles. They are correct until you replace the OEM tires.
 
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InTheWoods

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...You will not hurt a tire running it at max PSI, you will hurt a tire running it under and over loading it....
Surely you're not saying that anything less than the tire's MAX PSI rating is considered underinflartion?

The OP's question wasn't about 'hurting tires'. It was about the best pressure to run.

There is a 'sweet spot' between the tire's MAX, and the best pressure - and wouldn't that be what Kubota would publish?
 
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North Idaho Wolfman

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Surely you're not saying that anything less than the tire's MAX PSI rating is considered underinflartion?

The OP's question wasn't about 'hurting tires'. It was about the best pressure to run.

There is a 'sweet spot' between the tire's MAX, and the best pressure - and wouldn't that be what Kubota would publish?
I'm saying DO NOT read a book and take that as MAX pressure, read the tire itself.
No I'm not saying you have to run them at max.
But running them at max will get you the maximum weight/ Load rating for that tire.

I also have tires on my truck that take max of 80 PSI and I do not run them at 80 PSI unless I load the truck to max weight / load rating.
But I wouldn't read the owner manual and use that information to determine max pressure or load rating.
 
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DustyRusty

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Nope. Unless the tires are OEM. I would think the manufacturer would provide correct tire pressure for the tires they sell on the machine. Kinda like the pressure specs on the door panels of vehicles. They are correct until you replace the OEM tires.
I have a 1964 Chevrolet Corvair Spyder, and if you don't follow the tire pressures recommended by General Motors, you will not be driving that car very long at 50 mph, since it will spin out of control and most likely result in a crash. Doesn't matter what brand of tires are on the car, it is the front-to-rear tire pressure ratio that is important. Back in the 1960s many of the tire dealers didn't understand the handling characteristics of the Corvair and overinflated the front tires and had all 4 tires at the same pressure. That made the handling of the car more like trying to drive a squirrel. This is what led Ralph Nader to mistakenly say that the Corvair was unsafe at any speed. I have put thousands of miles on that car in the 30+ years that I have owned it, and I always have the tires inflated to what the manual says they should be. Doesn't matter if they are bias ply or radial tires, the front-to-rear pressure differential must be adhered to. I also agree with what N I W has said about tractor tires, and I inflate them to the maximum as indicated on the sidewall of the tire. With cars I follow the manufacturer's recommendation, on my tractor, I follow the tire manufacturer's recommendations. Trucks and trailers are another subject and I will leave that the those with more knowledge about them than I have.


699743-MVC-697F.JPG
 
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fried1765

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I have a 1964 Chevrolet Corvair Spyder, and if you don't follow the tire pressures recommended by General Motors, you will not be driving that car very long at 50 mph, since it will spin out of control and most likely result in a crash. Doesn't matter what brand of tires are on the car, it is the front-to-rear tire pressure ratio that is important. Back in the 1960s many of the tire dealers didn't understand the handling characteristics of the Corvair and overinflated the front tires and had all 4 tires at the same pressure. That made the handling of the car more like trying to drive a squirrel. This is what led Ralph Nader to mistakenly say that the Corvair was unsafe at any speed. I have put thousands of miles on that car in the 30+ years that I have owned it, and I always have the tires inflated to what the manual says they should be. Doesn't matter if they are bias ply or radial tires, the front-to-rear pressure differential must be adhered to. I also agree with what N I W has said about tractor tires, and I inflate them to the maximum as indicated on the sidewall of the tire. With cars I follow the manufacturer's recommendation, on my tractor, I follow the tire manufacturer's recommendations. Trucks and trailers are another subject and I will leave that the those with more knowledge about them than I have.


View attachment 123852
Beautiful!
Do you still have it?
 

NCL4701

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Most, if not all, tractor tire manufacturers publish charts with the specs for load capacity at various inflation pressures because they know that the tires are used for load carrying and traction, with the more important of those two varying depending on the application. Lower pressure is better for traction as it puts more bars on the ground. Higher pressure is better for load carrying as it increases load carrying capacity. There is some expectation by tractor tire manufacturers that the end user will apply some thought and research to tire ballasting and inflation to fit the job at hand. They don’t normally print the entire spec sheet for the tire in the sidewall. Maybe they should, but it would be pretty hard to read on the smaller tires.

Example: https://commercial.firestone.com/co...bles/Mar2015/Load and Inflation - Table E.pdf

High load (fronts on a tractor with loader) = max pressure as spec’d by tire manufacturer. More traction with max weight capacity not needed (possibly rears, depending on use) = possibly lower pressure than max rated.

For a basic discussion of tire pressure considerations for tractor tires (although it is also discusses tire type):

Run your tires at whatever pressure you want so long as it doesn’t exceed max on the sidewall. But if you want optimal performance, think a little about what you’re doing with the machine and what tire pressure is appropriate based on tire type and use.

The above has nothing to do with car, truck, airplane, or other type tires. High speed tires are a different topic. If you want to argue with the above in regard to tractor tires, take it up with the engineers at Firestone or Titan.
 
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85Hokie

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One thing to consider also - is that tractor tires ARE THE ONLY "shocks" on the machine.
Pumping those tires to max without placing a good load on them by whatever means will jar your teeth out and make you back hurt more than it should!!!
 
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GeoHorn

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Wow, really...
Do you run air planes tires randomly under inflated?
Do you run you car/truck tires randomly under inflated?
Remind me to never ride with you!

MAX tire pressure should never be chosen off of a book, as that info could be completely WRONG and could get you hurt.
The tire pressures listed on the side of a tire means that tire will perform and hold that pressure SAFELY per the manufacture of that tire, not some random figure that someone thinks up at random.
If you also note along with the pressure listing will also note a weight rating for that tire.
So you should take that into account.
Less pressure in a tire does NOT equate out to a higher weight load rating but a LOWER weight load rating and possibly tire damage due to under inflation!
The tires approved for a Hawker Jet which I flew as a production-test-pilot were to be inflated to 80 psi for turf runwys and 120 psi for hard-surfaced runways….. but were ”approved by the tire mfr’” …for pressures up to 210 psi. Why? Because the tire mfr’r had no idea which particular airplane OR operating weight Or runway surface-type would be utilized.

You can install an 8-ply rated tire on an auto which weighs 5K lbs …and the auto maker will recommend 28 psi…. but that same tire can be mounted on a truck which weighs 9K lbs…. and the truck maker recommends 42 psi…. while the tire mfr will have moulded on the sidewall “Max pressure 80 psi…” followed by the max weight-capacity that tire for which that tire was designed.

NIW… in a corollary…. A grade 8 bolt can be rated at 400 lbs torque….but if installed on a wooden picnic table…would you crush the timbers into splinters by using that torque..?

What WHEEL are those tires mounted on? Stamped sheet metal…?? or welded steel..?? ..or cast aluminum…??

The difference in what you NIW is posting in this thread…and what I am posting…. is that you NIW is posting the Max ALLOWABLE pressure as designed by the tire mfr’r….. and I am posting the recommended Max for best performance by the vehicle mfr’r.

Those criteria are Not the Same.
 
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NCL4701

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I am confused on the air pressure needed in my rear tires. L2800 Kubota has 11.2 x 24 Firestone tires. Kubota says 14 psi, Firestone says 26 psi max air pressure. I frequently fill the bucket with dirt and rock. So . . . what air pressure should I use?
To directly answer your question, assuming the full bucket of dirt is on a loader in the front of your tractor, max pressure allowable per the sidewall on fronts as max load capacity is needed in the fronts for the loads put on them in loader work. 14psi in rear is reasonable. A full bucket of dirt in a loaded bucket isn’t increasing the load on the rears. 14psi should give you about as much traction and ride quality as you can get without running a tire off a rim or having the rim spin while the tire stays stationary. Some run their’s lower, but personally I prefer at least a couple pounds safety margin.

That’s my opinion based on approximately 50 years and many thousands of hours operating various utility size tractors. Others may have other opinions and that’s their prerogative.
 
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GeoHorn

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To directly answer your question, assuming the full bucket of dirt is on a loader in the front of your tractor, max pressure allowable per the sidewall on fronts as max load capacity is needed in the fronts for the loads put on them in loader work. 14psi in rear is reasonable. A full bucket of dirt in a loaded bucket isn’t increasing the load on the rears. 14psi should give you about as much traction and ride quality as you can get without running a tire off a rim or having the rim spin while the tire stays stationary. Some run their’s lower, but personally I prefer at least a couple pounds safety margin.

That’s my opinion based on approximately 50 years and many thousands of hours operating various utility size tractors. Others may have other opinions and that’s their prerogative.
What about when the operator has an Empty Bucket …while traveling empty back-and-forth from the source?

While that practice (max tire mfr statement) is unlikely to cause much issue….. I disagree with the ”need “to use max pressure “per the sidewall”…. as when empty it will cause excess wear on the center of the tread area…while doing nothing beneficial for the tire when carrying a load….(in-fact, will cause excess wear on the center of the tread during load-carrying ops as well.)

The Tractor Mfr’r and FEL Mfr’r both Know the maximum rated lifting capacity of that tractor, it’s front axle, And the loader. The front tire pressure recommended by the tractor/loader combo is what should be utilized….as that is what will meet the needs of that lifting capacity.

The one on the tire sidewall probably won’t hurt anything…except the Tire… …. but it’s not necessary to stress the wheel, the tire, or the equipt by doing so…
 
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