Liquid ballast applies weight to the outer tread with different dynamics than does a axle centric wheel weight. This matters in the physics of that weight as rears are very large diameter. The rears still "squoosh down" to make traction, even with fluid in them and the ballast is at the point of ground contact, not up around the axle.
I served my apprenticeship as an industrial mechanic/millwright in a very modern program-honestly said it was far more sophisticated than much of the "wall paper of diplomas" I got from various college diplomas. We were once shown a Goodyear film series centered on their tire testing tracks. Zero was said about AG tires built on machines I serviced which were patented in the years prior to and just after WWI mind you! But I do recall that with road tires the entire issue of traction is tread contact based not on how much the car or truck weighs above the ground.
As a lifelong sine 1963 motorcycle rider, yet again, it's that contact patch that matters and fluid at the ground contact spot matters more in my feeble, aged senior mind.

Of course lowering air pressure can assist too.
I'm not playing math guru here but fact is that wheel weights are mostly always expensive and usually far lighter than weight using fluid. Fluid is not that hard to do on the farm if your retired like me and don't clock in, etc.. The freezing aspect is well covered in modern ballast fluids?
On the R14's I asked any number of dealers when I was pricing new tractors and very few like them as they all seem to say they load up with mud even more easily than do R4's. I suppose since they are not the typical option from distribution they might lean away as a sales ploy but the tread design does have close block spacings at that. I find that with R4's they will load after only a few wheel spins when skidding logs anywhere except on pasture turf when very dry. In the winter they like to stay that way too. AG1's are no doubt the better dirt tire tread but not common in these compact & utility tractors mostly seen here on the web.
I'm looking forward to seeing what this 4820R will do with my local mud? I gained ~ 1,400lbs plus my liquid ballast and a wider rear of same diameter as my Kioti so it should do more work. Got a white oak about 125-150 years old laying up there to test on.
