Tires Partially Filled Rear Tires

[Josh61513]

I've been doing some work on uneven ground and moderate hillsides this year. I would like to improve the stability of my tractor - Kioti CK20S (22hp Kubota B sized CUT with a strong loader for those who aren't familiar). I've already got wheel wieghts on order, I like the idea of these because I can take them on and off as needed.

Loading my rear tires would certainly improve stability but since I do use this tractor to mow grass with I'm hesitant add whatever these tires can hold (300-400 lbs.?) at 75%+ full. This is already a ~2,200 lb. tractor with the loader removed, probably 2,500 lbs. with the MMM. It's my understanding that its industry standard to fill the tire with the valve stem at 12:00 which results in about a 75% fill, leaving some room for an air coushin & expansion. Since the most benefit to lowering my COG is with weight as low as possible, what would be the drawback of filling to say 25%? Anyone tried this? Is the "sloshing effect" noticable? Does it hurt the rim to be constantly dipping in and out of the fluid?

To be clear, I'm not looking to add fluid to the tires to act as a counter-weight for the loader, only to improve hillside stability.

Thanks in advance!

-Josh

 

[sweettractors]

If you could somehow figure where the gravity centerline is on your tractor, it seems you could put fluid in the tires up to that point without defeating your stated purpose. Ken Sweet

 

[mustangsallysdad]

Pretty simple, really...do not fill above the centerline of your axle. No need to determine the center of gravity as this is a fixed low COG point on your tractor (or any tractor for that matter). Clock your valve stems at 9:00 or 3:00 and fill to that point. Anything above that point would be raising the COG.

 

[gauthier]

Well,try it and see,you can always let it out,,,You got ind or ag tires? maybe turf??

 

[rjkobbeman]

Would having half-filled tires cause stability problems because of the liquid sloshing around... kind of like a tanker without baffles?

I know you never fill your tires 100%, but at 75% (or whatever the recommended amount is) there is less room for the liquid to move around.

 

[sweettractors]

Pretty simple, really...do not fill above the centerline of your axle. No need to determine the center of gravity as this is a fixed low COG point on your tractor (or any tractor for that matter). Clock your valve stems at 9:00 or 3:00 and fill to that point. Anything above that point would be raising the COG.

So, you are saying that you could Theoretically, run a rod through the axle and out the front of the tractor and it would balance? (rotate like on a barbecue grill) What about the same tractors with different diameter tires? COG the same? Ken Sweet

 

[k0ua]

I filled to about 55- 60 percent, 25 gallons in a 15-19.5 and it is stable in all conditions. Sometimes can just barely hear it, never noticed any sloshing instability. I think the pool of fluid if viewed with x-ray vision would just pretty much lay at the bottom of the tire without much if any side to side motion. Take a child's vinyl pool inflatable "donut" toy and put some water in it to visualize what I mean. I wanted some extra weight, not just the stability, I used poly-ethelene glycol. (RV antifreeze). I would have used Rimguard, but could not find any nearby. It was easy to do, kinda expensive (4$ per gallon) but really works great for extra stability and safety.
James K0UA

 

[Diamondpilot]

With that little tractor its not going to do any harm loading the tires. What kind of weigh are we talking? Maybe 300#....

I have mowed with my 5,200# tractor and loaded rear 12-24" tires for 7 years with zero damage. I also have 4 suit case weights on the front and cast iron rear wheel weights on the rear wheels in addition to the loaded rears.

Just watch when you mow. My yard has great drainage so I can mow the day after it rains.

Chris

 

[CharlieS]

Would having half-filled tires cause stability problems because of the liquid sloshing around... kind of like a tanker without baffles?

Thinking in terms of a tanker without baffles, that would be linear motion with the liquid being able to get a "run" for slop and slosh the length of the tank.
Imagine a tractor tire xray with the tire partially filled with fluid, the wheel itself would be a baffle, plus the circular shape of the tire itself would prevent much of the linear motion found in such as a 40 foot long tank. Liquid movement shouldnt present much of a stability issue.
Viscosity will also play a part here. (thinking in terms of the tanker scenerio) thinner liquids have more movement in an allotted timespan than thicker liquids.

So, you are saying that you could Theoretically, run a rod through the axle and out the front of the tractor and it would balance? (rotate like on a barbecue grill) What about the same tractors with different diameter tires? COG the same? Ken Sweet

I think a more apt description would be a balance/counterbalance example. even though centerline may not be a balance point, with a top heavy object, adding more weight to the "bottom half" would change the weight ratio, and adding enough weight would then make the same top heavy object, bottom heavy, thus increasing stability.
track width will also have a bearing on stability though.

 

[Josh61513]

I'm sure the center of gravity of the tractor is above the axle centerline. There is very little mass below the axle but plenty above it, especially when the loader is full and lifted. Where exactly it is changes depending on the position of the loader and would be very difficult to determine without having a 3D computer model of the full tractor.

My reasoning in filling say 25% is because that's where the weight by far adds the most benefit for stability, but I don't want to make my tractor much heavier. I already have to be concious of when I mow relative to the rain as I have a good amount of clay in much of my yard.

I'm curious if anyone is aware of any short or long-term ill effects of doing this: sloshing, rim issues, etc.

I have industrial (R4) tires for those who were curious. They are ~33" tall, 12-16.5.

Thanks for the comments all, and 1st hand experience k0ua