Any good reason for oversize tires?

[Dr.Theopolis]

The specs on my rig call for 8.75 R 16.5 but all of the tires on it now (I just bought it) are 9.5 R 16.5. Is there any good reason to purposely put oversize tires on an RV? (mine is 1977 Argosy 24)

[kennethowens]

Shouldn't the wheels be 15's......and the tires ST225/75R15

[Phoenix]

16.5-inch rims are old pickup truck-size rims. There is very little selection in tires for that size anymore. Most old pickups are switching to 16-inch rims to get a better selection in tires (that's what we did with our old 78 chevy pickup before we sold it).

Costco still carries one tire, I think; but if you don't like what they have, that's it. Discount may be able to order some...

[Mike Leary]

Any time oversized tires are installed, the wheel bearings will suffer.

[Dr.Theopolis]

Originally Posted by kennethowens

Shouldn't the wheels be 15's......and the tires ST225/75R15

The specs - both in owners manual and on specs placard in the RV - call for 8.75 R 16.5

[Dr.Theopolis]

Originally Posted by Phoenix

16.5-inch rims are old pickup truck-size rims. There is very little selection in tires for that size anymore.

I have found many sources for the 8.75 R 16.5. They are plentiful but the 9.5 R 16.5's are fading out. I found a local source tha thas 6 of them left.

I'm just wondering why a previous owner put the 9.5's on. Better handling? Is it really that much better? Engine rpm's should be lower. Lower enough to make any difference on anything, like engine temperature, fuel consumption?

[Beginner]

The way the story was relayed to me was this:
the 16.5 inch tire was the first tubeless truck tire of Load Range D and above. It was made 16 so people would not try and put it on the old 16 inch rims that were available at the time. Andy of Inland was correct in saying that if you place a higher rated tire on an old rim that had been running a lower rated tire there was an excellent you would experience rim failure. If you will notice the 16.5 tire the bead sealing surface is at an angle not flat as on the majority of tubeless tires today.
That being said, identify the load range of the old 16.5 inch tires.
Determine the Maximum Width (at the fatest part of the sidewall)
Determine the Maximum Outside Diameter of the old 16.5 inch tires.
Go to a reputable tire dealer to determine the equalivant tire side and buy new rims, preferrable steel if this is a motor home.
The cost of the 16 inch truck tires is considerably less per tire than the same 16.5 inch tire.
If the wheel 8 lugs you will probally find that any 8 lug 16 inch truck wheel will work.
I changed my GMC van from 16.5 to 16 (8 lug wheels) and have one GM wheel, two Chrystler wheels and two Ford wheels (a spare). It has been doing fine for 6 years now.
Beginner