Wolbert,
I orginally wanted the ag's, but changed to the R-4's. The ag's were taller, and very very close to the rear fenders.
R-4's grip very good, ( I didn't think they would grip this good, might be the weight of the tractor too), and are more puncture resistant.
The ag's rubbed the loader frame, see the nice cut in the tread.
RedDog