Tires: Motorhome replacement tires, replacement tires, foot class

Question
I've been replacing the tires on my motor home 2 at a time (there are 6). The first two were replaced with 225/79R19.5, the second two a month later with 225/70R19.5. Now I've got the money for the last two. Which rating would be better? It's 24 foot class A motorhome.

Answer
Jerry,

First, this is "sizing", not "ratings".  It deals with the physical dimensions and by extension, the load carrying capacity.

But a 225/79R19.5 (emphasis on the middle value of "79") does not exist - and - the only thing that makes sense is if the middle value is "70", just like the second size.