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Old 07-29-2015, 08:53 AM   #1
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Changing tire size on 22.5 rims

We're about to take possession of a 2007 Dolphin LX6320 (34') with 22.5 in rims. The tires are original from the 1/2007 build. I do not have the DOT code, but suspect they were made before 1/2007. The Michelins I intended to purchase (235 80 R 22.5 - stock size) are currently unavailable and no date of availability is known. I have read where there are tires one size taller, and one size shorter (diameter) that are often used as replacements, as the 235's were a special size, and are often unavailable. Have any of you gone to either alternative size, and what were your experiences with same? The Dolphin is on the Workhorse chassis with the 8.1 Ltr. GAS engine, and I will be towing a Jeep "towd". Any recommendations would be most appreciated! Thank you in advance!
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Old 07-29-2015, 09:00 AM   #2
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I would think in terms of upping the size and getting a little more Rev's per mile as to decreasing the size. Shopping for Tires is a PIA and finding what you want or need is out there.
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Old 07-29-2015, 09:15 AM   #3
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Changing tire size on 22.5 rims

Your 235/80R22.5 Michelins are 556 revs/mile, load range G.

Goodyear makes the G670 MRT 245/75R22.5 at 560 revs/mile, load range G.

Your tire dealer may have more options, but not all companies publish detailed specs on their websites. They want the tire dealer to do that for you.

EDIT: Your wheels are almost certainly 22.5 x 7.50. It's probably best to stay with tires that work best with your wheels. Many companies make 255/70R22.5 tires in load range H at about 566 revs/mile, but a lot of those list 22.5 x 8.25 wheels as the preferred size.

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Old 07-29-2015, 09:24 AM   #4
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I would do anything to keep from using Michelin. Up one size should not be too big a problem.
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Old 07-29-2015, 09:54 AM   #5
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Changing tire size on 22.5 rims

Quote:
Originally Posted by NHRA225 View Post
I would think in terms of upping the size and getting a little more Rev's per mile as to decreasing the size. Shopping for Tires is a PIA and finding what you want or need is out there.

The relationship between revs per mile and tire size (diameter) is the opposite of what you think. As diameter increases, revs per mile decreases. As diameter increases, torque applied at the road surface decreases. I generally try to avoid this, especially for towing. I am happy to buy a slightly smaller tire than stock, with more revs per mile and more torque, but I wouldn't go the other way. To make things worse, increasing truck tire size often increases the load rating, which adds tire weight and stiffens the ride. It's bad from every angle.



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Old 07-29-2015, 10:44 AM   #6
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I went to 255/70/22.5 and everything is just fine. Don't miss Michelins ( especially the price). 255/70/22.5 is a readily available size all over the country.
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Old 07-29-2015, 03:04 PM   #7
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I changed size almost two years ago, and I am pleased with the results. Here is my original write up.

Changed My Tire Size
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Old 07-29-2015, 03:18 PM   #8
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Changing tire size on 22.5 rims

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Originally Posted by BigBadDad View Post
I went to 255/70/22.5 and everything is just fine. Don't miss Michelins ( especially the price). 255/70/22.5 is a readily available size all over the country.

Changing from "boutique" RV sizes to equivalent huge-volume truck sizes is an attractive option. I went from 255/80R22.5 to 275/70R22.5. I stayed with Michelin, but there were a dozen attractive models in the new size, compared to an often-unavailable Michelin-only size. I carry an unmounted spare, so it will take quite a mishap to keep me down for long.



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Old 07-29-2015, 03:44 PM   #9
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Checking minimum spacing between duals

It may not be a problem at all, but it's wise to check the tire manufacturer's minimum center to center spacing when you go to a larger tire.
Keep in mind that the tire size, such as 255 or 275 is the WIDTH of the tire. The 70 or 80 is the ratio between width and tire height.
When you change from a 255 to a 275, you've decreased the spacing between the dual rear tires by 20 mm. (1/2 the sum of the two tire's increased width.)
Every tire manufacturer who makes a truck/RV tire that might find itself on dual wheels provides a minimum center to center spacing for that tire.
Under standard loading conditions, tires don't touch, but on turns if underinflated or if one goes flat, that spacing is critical. It prevents one sidewall from rubbing into the adjacent tire's sidewall and destroying the other tire.
If the tires are too close together but not touching under normal use you won't know you have a problem until things go bad. Then they could go very bad very fast.
Vehicle manufactures use wheels with different offsets to provide the correct spacing when a tire/wheel combination is selected for a vehicle.
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Old 07-29-2015, 06:00 PM   #10
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Quote:
Originally Posted by garyvont View Post
We're about to take possession of a 2007 Dolphin LX6320 (34') with 22.5 in rims. The tires are original from the 1/2007 build. I do not have the DOT code, but suspect they were made before 1/2007. The Michelins I intended to purchase (235 80 R 22.5 - stock size) are currently unavailable and no date of availability is known. I have read where there are tires one size taller, and one size shorter (diameter) that are often used as replacements, as the 235's were a special size, and are often unavailable. Have any of you gone to either alternative size, and what were your experiences with same? The Dolphin is on the Workhorse chassis with the 8.1 Ltr. GAS engine, and I will be towing a Jeep "towd". Any recommendations would be most appreciated! Thank you in advance!

Contact Simple Tire, they have your size tire available. www.simpletire.com

Just had 255/80/22.5's delivered yesterday, date code three weeks old.

Cheers!
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Old 07-29-2015, 06:50 PM   #11
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I used to have the 235's but they are very hard to find. I switched from 235/R75 22.5 to 255/R70 22.5. The 255's are a common bus/truck tire and are plentiful on the road. The main requirement was I had to have 7.5 inch wide rims so I lucked out I guess. After two blowouts I don't miss the Michelins and although I know they make good tires I don't miss them.

The speedometer reads 2 percent off but I put a correction into the VMSpc and display the proper speed.
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Old 07-29-2015, 09:25 PM   #12
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On Simple tire website

:In Stock tire
$438.99
per tire

Michelin: XRV
- 1 Reviews
Tire Size: 235/80R-22.5
Part Number: 87511
Sidewall: BW
Load Range: G (14 Ply)
Calculate Shipping Buy Now
FET: $11.06 per tire
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Old 07-29-2015, 09:37 PM   #13
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You can compare various tire sizes here: https://www.tacomaworld.com/tirecalc....5-275-70r22.5

My prior MH originally had the 235/80 22.5, I went to 275/70/22.5, worked well and you can see there is very little difference except tread width.
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Old 07-29-2015, 09:51 PM   #14
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Quote:
Originally Posted by Hooligan View Post
You can compare various tire sizes here: https://www.tacomaworld.com/tirecalc....5-275-70r22.5

My prior MH originally had the 235/80 22.5, I went to 275/70/22.5, worked well and you can see there is very little difference except tread width.
Not a bad idea. What rim width do you need for the 275's???
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