However, backhoe weight and 3pt hitch capacity are somewhat related, as to the stresses and strains that they put on a machine while driving it around. My owner's manual states nothing about removing liquid tire ballast when utilizing the maximum rated load capacity of the 3pt hitch. Only when installing the backhoe.
My point is that if the weight inside the tires plus the weight of the backhoe would put too much strain on the drivetrain components, which is possibly the reason for the recommendation to remove the weight from inside the tires, then why will 1700 -2000 lbs hanging off the 3pt hitch, which is significantly more than the weight of the backhoe, cause any issues?
Is there a bigger issue that we are all missing that you are aware of, but have yet to enlighten us on, as to how tire ballast & backhoes are RELATED, yet tire ballast and 3pt hitch loads are UNRELATED? Could you please finally provide us with a detailed, informative explanation to this question?
The only way in which they are "related" is that BIG'er tractors typically have BIG'er lift capacities and BIG'er tires, it is therefore possible to get more liquid ballast in the tires.
Tire ballast is still un-carried weight, it is a convenient counter balance to the loader bucket as well as directly applied mass to the rear drive wheels, so it is a convenient (space efficient) way of adding traction for ground engaging implements.
A hoe "hangs off the back" and the more massive the tractor the more stable the hoe.
My hoe probably weighs about the same as my tire ballast, ~1100 lbs each, and I regard the 1100 or so pounds of tire ballast as a useful addition to the tractor/loader mass of around 5300 lbs when hoe'ing.
I still try to fill the bucket with dirt before setting it down to dig with the hoe.
All this adds up and helps me not drag the tractor and myself into the holes I dig.
I think the only "bigger issue" is with Kubota's failure to explain the "advice" to use un-ballasted tires with their hoes.
The earlier explanation that it MIGHT be (fear of) a liability issue with the rating of the ROPS seems likely to me.
Lets see; If my tractor rolled over with un-ballasted tires the rear wheel that would be up in the air would weigh somewhere around 400 lbs.
Same/similar rollover with ballasted tires would have a 950 lb or so loaded wheel up in the air.
That is just the static condition.
I speculate that WHILE ROLLING the additional mass could accumulate sufficient more energy to complete the roll, e.g. it could make the difference between on it's side or on it's roll bar - with an extra 1100 lbs in the tires (and the ~1100 lb hoe).
So; IF a tip-over "happens" you might be better off with no tire ballast.
If you ballast the tires I think the tractor is less likely to roll over, under same/similar circumstances, though once tipped it is more likely to roll completely.