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Open Roads Forum  >  Class A Motorhomes

 > 22.5 dual tire replacement .... which will fit?

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Scatback

Sun City West, Arizona

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Posted: 06/01/10 01:41pm Link  |  Print  |  Notify Moderator

I intend to replace my 235/80/R22.5 Michelin XRV tires on the rear duals shortly. Not being real fond of Michelin's price, I researched other brands...specifically Bridgestone and Yokohama. I see neither of these manufacturers has a 235/80/R22.5 size. This size must be made only by Michelin. Has anybody replaced their rear duals with an alternate brand and size without any problems such as speedometer errors, tire rub, etc?


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sprintmod1

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Posted: 06/01/10 09:08pm Link  |  Print  |  Notify Moderator

Just replaced our Micheline XRV's with Toyo M154's; replaced with 245/75R22.5; have put over 1500 miles on them so far and ride is much smoother and we seem to have gained 3/10 to 4/10th of a mile per gallon in fuel milage.


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fcooper

Richmond Hill, Georgia

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Posted: 06/01/10 09:35pm Link  |  Print  |  Notify Moderator

Here's another thread with the same question, and has a comparison between your tire size and a 275/70R22.5

Thread about XRV 235.80 22.5

Don't forget to carefully dual spacing.


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psyflyjohn

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Posted: 06/02/10 07:02am Link  |  Print  |  Notify Moderator

Replaced my Michelins with Toyo M154's about a year ago. Love em. Good tires.


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wolfe10

Texas

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Posted: 06/02/10 07:46am Link  |  Print  |  Notify Moderator

What size wheels (look at outer rear dual for numbers)? That will also limit options and also sets wheel offset.

And MPG change with change in tire SIZE is suspect unless the speedometer/odometer is re-calibrated to account for the change in "revolutions per mile".


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UltraKen

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Posted: 06/02/10 02:30pm Link  |  Print  |  Notify Moderator

You need to check the tire specifications from each manufacturer for the size you currently have and any change in size you are contemplating.

Usually you will find the tire diameter, approved rim width, tire width, minimum dual spacing, and Revolutions per mile.

It also helps to have the wheel offset, obtainable from the wheel manufacturer's site.

There are two ways to estimate dual spacing. The first is to compare tire width with minimum dual spacing. The width must be less than the minimum.

You can check your current spacing by measuring from the first rib of the outer tire to the first rib of the inner tire. Subtract the tire width from the measurement across tires and you have the current spacing.

The other way to estimate proper spacing is to multiply the wheel offset by two, and then subtract the width of one tire. Ex. My wheels have a wheel offset of 6.44", doubled is 12.88. The tires I selected are 10" wide. The dual spacing would be 2.88".

Using either method (rib to rib or wheel offset) the estimates are very close.

You should also measure the approximate distance from the outer tire to the edge/surface of the wheel-well. If the replacement tire is 1" wider than the current tire than half that extra width will be on the outside and that much closer to the plane of the body at the wheel-well.

Summary:
1. Tire Revs/mile should be very close. My old 9R22.5s were 543 RPM. my replacement 265/75R22.5s are 540 RPM (about 1% difference).

2. Approved rim width must match actual rim width of your wheels.

3. Tire widths must be close. My 9Rs were 8.9" wide, the new 265/75s are 10" wide.

4. This leads to dual spacing. Subtracting tire width from 2 times the wheel offset gives 3.98" for the 9Rs and 2.88" for the 265/75s. still plenty of room for cooling between the duals.

The bonus: Going from the "inch-standard" (9R) to the metric standard 265/75s meant going from an F rated tire to a G rated tire. I've also got a total of 6" more rubber width on the road, AND based on the coach wgt I am able to go from 85psi front/90psi rear to 75psi front/80psi rear which will give both more wgt capacity and a softer ride.

I've added a spreadsheet that I used to make my comparisons. Towards the bottom is a 3 line set of numbers that is just to do the subtraction of tire width from 2xoffset.

Spreadsheet

* This post was edited 06/02/10 02:40pm by UltraKen *


UltraKen
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