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  1. #1
    Elite Member
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    New Brunswick, Canada
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    Kubota L5030 HSTC, MF 5455

    Default Kubota Corp and weight boxes vs loaded tires

    The dealer was telling me kubota is pushing hard to eliminate loaded tires in all sizes of tractors, he didn't know why and says they still load tires as they would lose customers.

    The fall flyer is giving weight boxes away with loader purchases with a slogan saying loaded tires are not the best solution.

    So why don't they say why they aren't the best solution?

    So far I've come up with my own list of comments:

    Weight box stresses the frame/castings more than loaded tires.
    Weight box can be removed when loader is off to better adapt the tractor.
    Loaded tires are always available for use.
    Loaded tires increase traction even when a rear implement is in use.
    Weight box takes weight off front axle while loaded tires don't.

  2. #2
    Veteran Member
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    Jun 2004
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    1,685
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    Northeast MA
    Tractor
    Kubota B3200 with BH77 backhoe, Kubota B50 SSQA w/ 54" & 60" buckets, LandPride FDR1660

    Default Re: Kubota Corp and weight boxes vs loaded tires

    The problem with comparing loaded tires to a weight box is that they aren't quite the same thing. A weight box gives you more weight out on the back of the tractor and works well if you are going straight ahead on a level surface. If you are thinking strictly of using a loader in this narrow circumstance then the weight box is actually better than the loaded tires because it has a better leverage effect on the front of the tractor. If you are using the loader and you have an implement on the back of the tractor and you are on turning on non even ground then the implement adds some weight to the back but if the implement is raised then may actually make the tractor more unstable because of the pendulum effect. This is the sort of circumstance that loaded tires help with. Loaded tires put the weight down as low as it can go on the tractor and have the effect of making the tractor stable in other circumstances other than just using the loader. A better comparison would be between loaded tires and wheel weights. For some reason it sounds like kubota does not want more weight on the rear wheels but they are not giving any explanation as to why. I know the factory manual and the owners manual for my BX23 both talk about loading tires and how to do it - but they also both say you should not use loaded tires if the backhoe is attached to the tractor. Since it is unlikely that I am going to either have two sets of tires - one loaded and one unloaded - and then change them every time I remove the backhoe, or that I am going to drain and refill the tires every time the backhoe is removed/added - the tires stay loaded all the time. My dealer did this and recommended loading the tires. I have never driven the tractor without the loaded tires in the rear so I don't have a comparison point between loaded/unloaded but I do know that there have been a few instances when I hit big dips or ruts and the tractor leaned heavily but never went over. Seems rock stable to me in this configuration. Since the backhoe adds weight up high I suspect that the loaded tires are actually a good thing with the backhoe attached. Sounds like Kubota has some splainin' to do if they are making this an official policy. Wonder if I can get a free weightbox out of them if I say my tractor is now unsafe with the unloaded tires in the back?

  3. #3
    Super Member Bob_Skurka's Avatar
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    Default Re: Kubota Corp and weight boxes vs loaded tires

    Jim, I honestly don't know if you are correct or not in your assessment of the weight box as used in a straight line with the FEL or not, but regarding the fact that loaded tires brings the weight down lower than a weight box, that is really something that depends on the size of the rear tires on the tractor.

    On a BX series, there is no question in my mind that a weight box would likely have more ballast weight ABOVE the ballast that a BX size rear tire would carry. There are TWO reasons why this would be true. One is the frame height of a Sub-CUT is low to the ground so the ballast in the weight box would have to basically be held at a very low level which is probably not practical when working, and the other is the aforementioned tire size issue.

    However, as the rear tire sizes get larger, the likelyhood is that the centerline of the axle, frame height, etc also is elevated substantially. So a ballast box can be held below the centerline of the axle and still have enough ground clearance for working purposes. Again, this is a rather grey area because a rear tire is only filled about 75% and if the ballast in the box is held too high on the 3pt, then the tire has the advantage.

    From the mechanical leverage point of view, 500# hanging 24" behind the drivers seat is better than 500# sloshing around inside the tire and has a greater mechanical advantage when used as ballast against a FEL bucket full of rock. I've never done the calculations but I suspect the fulcrum point on a tractor with a FEL is the upper pivot point where the loader arms attach to the vertical points of the loader attachment arms/tractor brackets. Moving weight, as far back and below that point is probably what kubota is trying to do with the ballast box.

    I use one tractor that uses a ballast box and one with loaded tires. Loaded tires are much more convenient!

  4. #4
    Platinum Member sneaky_pete's Avatar
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    Parker County, Texas and Santa Fe County, New Mexico
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    Kubota B7400HSD, G1800

    Default Re: Kubota Corp and weight boxes vs loaded tires

    The owner's manual for my B7400 recommends loading the tires, although I realize this is a discontinued model.

    My tires are not filled; since I have an FEL and pretty much leave it on all the time, I always leave an implement on the 3PH, by default my super-heavy Gannon box scraper if I'm not specifically using a different one. Haven't yet had any problems with this set-up, but I don't have any steep hills on my place and don't take that tractor in the creek or the ditch.

    Pete

  5. #5
    Super Member ronjhall's Avatar
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    SE Michigan, TX when its cold in MI.
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    Kubota 2910 HST

    Default Re: Kubota Corp and weight boxes vs loaded tires

    <font color="blue"> Weight box stresses the frame/castings more than loaded tires.
    </font>
    Please explain. I'm not sure this is true.
    It would take less weight in the weight box to get the same ballast that loaded tires would give.
    Loaded tire may put more stress on the drive train because of the centrifugal force of moving liquid.
    I have had tractors with both loaded and unloaded tires. I prefer the weight box. It give more flexibility to a CUT.

  6. #6
    Elite Member
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    Kubota L5030 HSTC, MF 5455

    Default Re: Kubota Corp and weight boxes vs loaded tires

    Ok this is a bit of engineering talk but... Take a 2x4 and hang the ends over the ends of two sawhorses. Basically so 1/3 hangs out past either horse and 1/3 between.

    Have someone stand on one of the overhung ends, put 2 people on the sawhorse farthest away to balance. Have all three jump and watch how the 2x4 flexs. This is loaded tires going over bumps.

    Next, put a person on each overhung end and have them jump, this is weight box on bumps.

    That 2x4 will bend more in the second case, this flex is proportional to the stresses.

    </font><font color="blue" class="small">( <font color="blue"> Weight box stresses the frame/castings more than loaded tires.
    </font>
    Please explain. I'm not sure this is true.
    It would take less weight in the weight box to get the same ballast that loaded tires would give.
    )</font>

  7. #7
    Super Member Bob_Skurka's Avatar
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    Default Re: Kubota Corp and weight boxes vs loaded tires

    slow. . . I think I'm inclined to go with Ron and then add one more thing, the 3pt is DESIGNED to handle the weight and the stress load that what it is there for. Your example makes some sence, but Ron makes (in much clearer language than I did) the same point I made. Put weight on the back and you need less of it than in the wheels.

    Now if you want to really start a discussion, what about simply using a heavier tractor? Many people contend that a heavier machine needs less ballast. Many contend that the heavy machines don't necessarily have the weight in the right place and are no better balanced that a light machine. . . therefore still need proper ballast when the situation calls for it (like FEL work).

  8. #8
    Elite Member
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    Kubota L5030 HSTC, MF 5455

    Default Re: Kubota Corp and weight boxes vs loaded tires

    Bob, I doubled my weight in the example but the weight on the 3 point still harder on the frame. If the frame can handle it on the 3 point it can handle it on the axles.

    I'm wondering if it is the reduced loading on the front axle issue? The weight box does reduce front axle loading.

    I've used loaded and unloaded tractors, the unloaded ones generally ride better. We are looking at getting an L-series kubota someday and I would probably need to load the tires for non-loader situations, ie moving heavy things down hill.

    So why not use loaded tires +weight box? Possibly too much traction leading to a twisted off axle?
    Ken

  9. #9
    Elite Member
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    Kubota L5030 HSTC, MF 5455

    Default Re: Kubota Corp and weight boxes vs loaded tires

    Re the bigger tractor, I agree, the extra weight isn't always where you need it for loader work. Even the ag tractor we use with cab, loaded tires isn't enough for dirt work. A heavy implement also needs to be hung off the back.

  10. #10
    Elite Member Cliff_Johns's Avatar
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    Northern Illinois
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    JD 4110

    Default Re: Kubota Corp and weight boxes vs loaded tires

    </font><font color="blue" class="small">( I'm wondering if it is the reduced loading on the front axle issue? The weight box does reduce front axle loading. )</font>

    I would guess this is the key reason. Loaded tires don't help reduce the weight on the front axle and kubota may have determined that loader work is causing dammage to front axles and wheels. Also, 3 point mounted weight reduces stress on the turning hydraulics etc.

    Cliff

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