The Beave
Georgetown TX USA
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Joined: 08/07/2002
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Our Beaver Monterey currently has 255/70/22.5 tires. However the wall data plate indicates the correct size is 9R-22.5.
These are apparently two different tire measurement systems. I know that the 255/70/22.5 tire is the larger of the two sizes.
So what size would the 9R-22.5 tire be if measured in the same system as the 255/70/22.5?
The Beave
30' 1997 Beaver Monterey
(The shortest DP we could find)
2005 Honda CR-V
Remco surge brake
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wolfe10
Texas
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Joined: 10/08/2000
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The 9R is closer to the 255/80R22.5
http://www.michelinrvtires.com/michelinrv/tires-retreads/tireInfo.do?tread=XZE#
Click on Specifications.
Brett Wolfe
1993 Foretravel 36' U-240
Cat 3116, Allison 3060
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Jarlaxle
New England
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Actually, a 265/75 or 255/80R22.5 is a replacement for a 10R22.5. A 9R22.5 is replaced by a 245/75R22.5 or a 235/80R22.5. (A 295/75 or 275/80R22.5 replaces an 11R22.5.) In all cases the metric tire is a bit (about an inch) shorter.
I'd probably keep using 255/70's.
John and Elizabeth (Liz), with 3 nutty cats
My beloved St. Bernard, Marm, lost him 1/2/12
Current rig:
1992 International Genesis school bus conversion
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wolfe10
Texas
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The Michelin XZE spec page:http://www.michelinrvtires.com/michelinrv/tires-retreads/tireInfo.do?tread=XZE
Click on "Specifications".
Suggest you read through all the specs, but Revolutions per mile is one of them:
9R 543
255/80 538
10R 517
235/80 555
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topflite51
In The Desert of Nevada
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Joined: 05/13/2004
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If your rim width and clearance are satisfactory on the duals I would stick to the 255/70's also. They are a little shorter and a little wider, and can be found in higher weight capacity rating. Because of the fact of being shorter, they do turn more revolutions per mile, around 20 I believe.
 David
Just rolling along enjoying life
w/F53 Southwind towing 87 Samurai looking to golf or fish
Simply Despicable 
Any errors are a result of CRS.
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TexasShadow
Spring Branch, TX USA
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Joined: 10/12/2003
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The 255x70rx22.5 is a very good choice if it meets your needs because all the truck stops that carry tires will have them. This size is used on many over the road trailers and they have a good carring capacity. I use and am very happy with this size Toyo tires.
TexasShadow
Holiday Rambler Endeavor LE/ 3126B Cat
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UltraKen
Ohio
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The best match to the OEM 9R/22.5s I found were 275/65 R22.5s.
See my notes in my signature below for some ideas about tire selection.
UltraKen
Ex - 1968 Ultra Van
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jgtown
SoCal
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As long as your rims are within the width range allowed for the tire, you don't exceed the weight capacity of the tire, and you've got proper clearance all around and in between, you're fine. Some tires are very specific about rim width, others can go on a wide range of an inch or more.
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