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Old 05-31-2012, 07:15 AM   #1
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Using A Different Tire Size Than Stock

Getting motorhome ready for the season I noticed several small cracks in the front tires. All of our upcoming camping trips are about 25 miles from home, so not a huge rush on replacing the tires, but in August we're driving 1200 miles to Sturgis SD and I will definately need to replace the tires before then. The size on it now is 235-80-22.5. So far I've only searched on line for pricing and have found some attractive pricing. My size is not as common as others though. I'm thinking of changing from the stock size to a 255-70-22.5. Here's how they compare.

Existing tires vs Tires being considered

Diameter 37.3" vs 36.56"
Width 9.25" vs 10.04"
Circum 117.19" vs 114.84"
Sidewall ht 7.4" vs 7.03"
Rev per mile 540.65" vs 551.72"
Speedo Corr 65 mph actual vs 63.7 mph actual

I would consider a 265 70 22.5 because there differences are even less. 65 mph vs 64.66 mpah.

Has anyone made a change along the lines of what I'm considering. Or perhaps there's a tire expert or former tire expert that can share their expertise and/or opinion. Or anyone else for that matter.

Thanks in advance for any feedback.
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Old 05-31-2012, 08:15 AM   #2
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The only real problem you run into is the space between the rear dual. If it gets too close heat builds up and can cause tire failure. I have also been looking and the 245/75/R22.5 is closer to the 235/80 R22.5 when it comes to overall width when loaded. An increase in cicumference can also increace the load on the engine and decreace in fuel milage so you wan't to keep this to a minimum because it will efect overall gear ratio.
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Old 05-31-2012, 11:24 PM   #3
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Originally Posted by speed racer View Post
The only real problem you run into is the space between the rear dual. If it gets too close heat builds up and can cause tire failure. I have also been looking and the 245/75/R22.5 is closer to the 235/80 R22.5 when it comes to overall width when loaded. An increase in cicumference can also increace the load on the engine and decreace in fuel milage so you wan't to keep this to a minimum because it will efect overall gear ratio.
I hear ya. I'm not planning on replacing the rear duals first time around. Just the fronts, to make it safely to Sturgis. Rear tires are in better shape and I don't think they'll fail. They'll have to be replaced next year though.
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Old 05-31-2012, 11:43 PM   #4
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One respondent on the Workhorse forum reported a rubbing problem with the 255's in front, when making a full lock turn, this will of course depend on the coach builders clearance. (he had to take them off). A lot of users of the 235-80's have gone to the 245-75's with no issues. The diameter there is only about 0.2 difference.
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Old 06-01-2012, 12:08 AM   #5
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Going to a different size can be problematic, or not. We went from 275/70's to 305/70's on the front as we needed the load capacity. (same capacity as the 295/80's but much smaller in diam). They're 1" wider and " larger in diam. than the 275's they replaced. Now I have to be sure my tires are turned straight when I dump the air or I'll destroy the fender flares.
I didn't need the higher capacity in the rear so I went with the same 275/70's as OEM size was.
Some have had to trim the jack pads or even the mud flap mounts.
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Old 06-01-2012, 12:10 AM   #6
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Quote:
Originally Posted by pkmesser View Post
One respondent on the Workhorse forum reported a rubbing problem with the 255's in front, when making a full lock turn, this will of course depend on the coach builders clearance. (he had to take them off). A lot of users of the 235-80's have gone to the 245-75's with no issues. The diameter there is only about 0.2 difference.
Thanks PK. Yeah I suppose that could be an issue. Just a FYI, here's the web site I've been using to compare tire sizes and dimensions.

Tire Size Calculator - Compare Tire Sizes
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Old 06-01-2012, 01:12 AM   #7
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I went to a completly different size on mine without any problems.
I went from a 11R22.5 to the 255-70-22.5 tires on the rear. (I was regearing anyway so the height change in the gearing didn't matter)
My new tires are load rated slightly higher which didn't matter but would help in that they should be more resistant to anything poking though the tread and makeing a tire go flat.

The 255-70-22.5 is I belive going to much easier to find than the 245-75-22.5 tires. THy might beless costly because of it. THat size is mostly used on trailers buth they are NOT marked trailer use only like smaller trailer tires.
On my vehicle there is plenty of room between the tires on the back.
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Old 06-02-2012, 05:06 AM   #8
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Originally Posted by Wolfpack Fan View Post
I hear ya. I'm not planning on replacing the rear duals first time around. Just the fronts, to make it safely to Sturgis. Rear tires are in better shape and I don't think they'll fail. They'll have to be replaced next year though.
Hi Wolfpack, Just because those rear tires look ok, maybe not showing weather cracks, does not mean they are in good shape. There is a DOT number on all tires. This indicates the birthdate of a tire. Example 1207; This tire was built in the 12th week of 2007. Anything beyond 7 years is asking for trouble. Very recently we blew a tire on our 2000 Malibu while being towed behind our MH. The DOT number was 0205. It was over 7 years old. 7 years is not a magic number, but bears watching. This little car tire did $2936. in damage. Think about a truck type tire coming up through the floor of your motorhome..... Other replies to your coment, mention a 255-70-22.5 I used these on a semi trailer. I would load 40,000# on the rear 8 tires. They are plenty heavy for a MH. hope this helps, old trucker
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Old 06-04-2012, 10:27 PM   #9
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Hi Wolfpack, Just because those rear tires look ok, maybe not showing weather cracks, does not mean they are in good shape. There is a DOT number on all tires. This indicates the birthdate of a tire. Example 1207; This tire was built in the 12th week of 2007. Anything beyond 7 years is asking for trouble. Very recently we blew a tire on our 2000 Malibu while being towed behind our MH. The DOT number was 0205. It was over 7 years old. 7 years is not a magic number, but bears watching. This little car tire did $2936. in damage. Think about a truck type tire coming up through the floor of your motorhome..... Other replies to your coment, mention a 255-70-22.5 I used these on a semi trailer. I would load 40,000# on the rear 8 tires. They are plenty heavy for a MH. hope this helps, old trucker
Sound advice. Thank you sir.
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