dooz

Thanks again, Bill! I got most of what I know from the site you suggested. I have two problems that site did not solve: 1. Ensuring enough space between duals. I haven't found any site or anyone who can tell me what that spacing is or should be, but I have in the past seen something about how there needs to be a minimum space/gap. The Goodyear site does list appropriate rim sizes (widths) for each tire size, but I don't know what size rims I have (old spec sheets don't say, and I don't know right off how to measure with tires still on--andTBH I'm trying to learn as much as possible while sitting at my computer-lol). (My logic: Compatible rim width ensures adequate spacing/gap.) (OEM size could fit on 6.75, 7.50, or 8.25, but 265/nn or 275/nn seem to need 7.50 or 8.25. So if I have 7.50 I'm good, but if I have 6.75, not so much.) 2. Which sizes that I can plug into the tiresize page are actual/common sizes. For example, I can input 275/75 (which gives me the closest match on diameter), but Goodyear doesn't list it. (Already had fun getting a tire while traveling to replace 755/70R22.5.) Anyway, hoping some retired tire person will jump on here.

My RV is: 2004 National TropiCal T396, Cat/Allison. OEM tires were Michelin 255/80R22.5. Can't determine (w/o measuring rim) the rim width. Thanks. Oh, and I found a chart of sizes, this one for Goodyear, which helps: https://www.goodyearrvtires.com/tire-selector.aspx

I don't know WHY I keep doing that! Those would be some super-fat tires! Yes, 255 and 265. And yes, I was believing the 0.8 inches less wouldn't be a problem, but I still don't know if this is a common/commonly-available size. Thanks for your input

My Type A pusher has 22.5 rims. OEM tires were 755/80R22.5, but only Michelin has this size. Tires were replaced before I got it with 755/70R22.5. These are about 5% smaller diameter, which means at an indicated speed of 60 mph, I'm only going 56 mph (and thus the distance I go is less than indicated and fuel mileage is less than indicated). I want to move to a tire size that is closer to OEM, but I worry about such factors as clearance between the duals. (For example, 765/75R22.5 has 0.8 in less clearance.) I also don't have a source for what sizes actually exist or are common. (Again, Michelin owns the OEM size, and my current tires are an uncommon size.) Any experts on here, or does anyone know a good Web reference?