It changes depending on the tire shop and Tire manufacturer. For 15 years Discount Tire Installed BFG 33x12.50x15 AT's on my 15x7 Bronco wheels and then I ran 35x12.50x15 AT's for years from Discount Tire until out of the blue the manufacturer changed their minimum wheel size to a 15x8. Then Discount Tire would not install them anymore, even though I had been a customer buying the same size on the same rim for more than 20 + years. It is completely safe to run 15x7 rims with 12.5" wide tires and I even beat my Bronco to death in the hardest parts of Baja and in the Dunes of Glamis aired down to 10 psi a bit low, but normally around 15 psi.
It did tick me off and I found a tire shop that would still put tires on my 15x7's and I never went back to Discount again. I did get some 15x8 rims for the Bronco, just because the old ones were out dated and I got a great deal on new 15x8 Craiger Soft 8 for $35 each. So I got two sets, one to run and another, I might convert to beadlocks.
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