Thanks, everyone. The rubbing on these old truck tires isnít very much Ė hasnít even taken off the molded-in lettering. I suspect itís a combination of the truck tires plus worn bushings (hope it isnít bent spindles Ė CNH site seems to say that LH spindles are NLA). Judging from the checking and weathering on these tires, it looks like it hasnít been a problem that any POs worried about (we got this tractor this last spring).
I also learned a lot from all of you - that the truck tires are slightly wider than the tri-ribs, that the 5.50x16s were options, that the wider 5000/7000 rims would fit (as I read it, CNH says those are 8Ē wide), and that flipping the rims has been done a lot. I also seem to remember someone (FordFarmer?) saying in a previous post that he prefers the tri-ribs in heavy clay.
I have to agree with the thought that the bearings, etc. are replaceable and that the extra wear from a stock flipped rim might be negligible, esp. since we donít use this tractor much, I donít push it hard or bounce it down the road, and it has a smaller bucket on it. Iíve been most concerned about breaking a spindle/axle. Bought this tractor because it has a stouter loader front end than our 3000 and didnít want to push it past its limits by inexperience.
Thanks again for all of the experience and advice.