Thank you for the replies. I realized after posting my question, why not upgrade the spare also. Saving $200 is not a game changer in dollars but having the correct matching tire could be.
I was aware Sailun had a 235/80/16 G tire but could not find it locally. I will have to do more checking. Can those of you who have the 80 series S637 tell me where you found them? My local Big O tire center says they can only get the 85 series tires. Having the 80 series would be nice then I would only need to change 4 tires not 5.
How do you like the Sailun G rated tires and do you run 110 psi or follow an inflation chart similar to Goodyear?