I don't know how much you know about modern manufacturing, but what you are saying is simply not possible. These tractor companies, as well as their suppliers have their inventory levels calculated down to the day, hour, minute. Literally. I've been to the Kubota factory in GA and they hold about 20 minutes worth of inventory on the production line. The suppliers work just the same way as inventory overhead kills profitability. They don't build tires and make one stack for Deere, and one stack for everyone else. They knock out whats required for that day and get it out the door. If a vendor had tolerance problems like you describe, their days in business would be very short.
Incidentally, as a retailer I can never recall us replacing a set of tires on any tractor, from any vendor because the rolling diameter was different. The standard of initial quality thats put out today is far beyond whats been put out over years past.
A few may, but not many. This goes back to my statement that what Deere has done best is the way they sell themselves. Unless they start selling complete and utter crap, people will continue to buy because of their perception of the company as a national icon of sorts. Deere people, but Deere equipment... then there is everyone else. We see very few customers crossing back and forth between brands. The product is pretty much irrelevent, thus why they have gone to marketing other companeis equipment under their name and selling more and more economey lines from India, China, etc.
