Combines 9650 sts tire sizing

nod, I think you should look at the operators manual to see how much adjustment you have on the front and rear axles. I find it hard to believe that there is no adjustments. On the CIH machines the front planetaries have two sets of bolts that lets you raise the machine about 3". On the rear, the 4wd axle has 4 positions, I'd say about 6" of adjustment. That lets you get pretty level with nearly any tire combo. As for what tire size you need on the rear, it all boils down to how much weight you will have to carry and how fast you will be going with that weight. The limiting conditions for the rear of a combine are in the field full of grain going slow and on the road with no header going 20 mph. If you can determine how much weight you will have on the rear in both cases, I think I can tell you how much air you will have to run for the sizes you are considering. After you get down to about 6 psi, there is probably not much reason to go lower.

At a fixed hydrostatic pressure, taller rear tires produces less tractive effort than a smaller one. So, if you want the rear to push hard, be careful what size you chose. You may wind up trading traction for floatation. Do you know of anyone who has tried metric 600mm wide tires with R1W tread on 26 or 28 inch rimsIJ