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Given the age of the RV , I doubt that the tires are original equipment. So going by the tag in the RV would be questionable. You need to look at the tire sidewall for " Max inflation cold " info.
Also there should be a 4 number code on the side wall to tell you when the tires were manufactured ( I'll see if I can track down a photo ) the first two numbers indicate the week and the last two the year.
E.G. 3505 will mean 35th week of 2005
If the tires are more than 7 years old , NO MATTER HOW GOOD THEY LOOK , they are due to be replaced before a trip.
Weighing the RV and getting a proper inflation chart from the tire manufacturer are in order.
EDIT>Pictures and links to info in this post.
Goodyear G159 tires