Why upsize the front wheels if the two tractors use identical gear-sets? According to Mitsubishi tractor date, the standard turf front wheel/tire size for both tractors, the Beaver III S373D and the Buck S470D are exactly the same, that being 6-12. Also, according to their data, the rear standard turf tire size is 9.5-16 for the Beaver III and 9.5-18 for the Buck. IF the tractors are exactly the same in respect to all mechanical components, except for engine and rear wheel size, it implies to me that the rear wheels could be interchanged. I am inferring from this that the reason Mitsubishi equipped the Buck with larger rear wheels is because it has sufficient additional engine torque to drive them. With the Beaver III having a smaller engine, I am also inferring this is because the engine has less torque, but enough to drive the smaller rear wheels but not sufficient for the larger size used on the Buck. My wheel/tire size question about the interchangeability of the rear wheel/tires from the Beaver III to Buck was posted in case someone who had a rear pair from one of these tractors, but only had the other tractor on which to use them. My understanding has been that a 3% variation up or down in tire size was still within the acceptable range the transmission gear-set could manage without binding up. If that assumption is correct, is this how Satoh/Mitsubishi could successfully use the same gear-set in both tractors while having different sized rear wheel/tires on these two models?