Sounds like a a plan, but keep the following in mind. The weight rating of the tire shown, when ran as a single tire on each corner, is more appropriate to the 425 than the 1850. Here is why!
Think of it this way; when you lift a full bucket of material (or even one a little over full) the full weight of the contents of the bucket and most (or all) of the weight of the tractor rests on the front wheels. In the case of a 425, with 800 lbs. in the bucket, that is greater than 2400 lbs. with a rider is on board. A 1700 pound tire limit would provide a working rating of 3400 lbs, plenty of margin to cover bounce, roll of the tractor (putting more weight on one side vs. the other, etc.
The back tires carry only the tractors own weight and only about half at that. This makes the back a non-factor in figuring the tire ratings.
3400 lbs. would be far too light for a 3600 lb. tractor lifting 1200 lbs. This places over 2400 lbs on each of the 1700 lbs tires. Running duals might be fine provided both tires share the load when loaded. This means both tires of a dual set MUST carry the load because letting one tire (even when driving over a rock) carry the load by itself puts it 50% over its rated capacity.
Since you already have them, what are your thoughts about running these on the rear and 4-ply tires up front?
Back to the smaller machines...These tires do pose a serious delema for me as a PT-422 or PT425 owner. They are the right weigh rating for my machine, but just a bit larger diameter than my current 22" tires and the 20 incers found on the current 422. They would add a bit more ground clearance but require a bit more torque to turn. They have me interested as I need both new tires and new or rebuilt wheel motors. If changed the two out together, I could add displacement to the motors gaining torque and loosing speed, in proportion to the increased tire size. I gain 1" ground clearence but could maintain speed and tractive effort as designed. Hmmm? What to do?
