Very interesting information.So, my R14s are more "rounded" than R4s, so even filled, they are better on turf than R4s. I dont know that All R4s are squared off, or that All R14s are rounded, so your milage may vary
I went looking trying to see what you're talking about with the squared vs rounded tires.
Are you talking about how the centerline of the tires balloon out, or not, compared to the sides? Or how sharp the transition from the side of the tread to the side wall is?
The R14's I see (Goodyears according to the Kubota options) are a bit ballooned out on the centerline, but not very much. The sides of the tread, however, cut off very sharp at the edges by the side walls.
Also of interest - the R3 turf tires I see "balloon" out more, however they still have the sharp edges by the side walls. That puzzles me a bit.