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Author Topic: Tire size 12r 22.5  (Read 1961 times)
Busnut83
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« on: May 02, 2009, 04:34:50 PM »

    
Re: Tire size 12r 22.5

My question is can I switch my front 12r22.5 tires and wheel with a 11r24.5 on my 83njt mci-9 .  I will still run the rear 4 and tag with 12r22.5.
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HB of CJ
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« Reply #1 on: May 02, 2009, 08:42:09 PM »

Keep the 12RX22.5's on the steering axle and swap out all the rear and tag wheels with the 11RX24.5's?  Slightly more front end tire and wheel capacity?

It's my understanding (someone correct me if wrong) that the rolling diameter of the 12RX22.5 and the 11RX24.5 are ALMOST the same at around 130" circumference?

And the final option that should also work would be to switch out ALL the tires and wheels with the 11RX24.5, expecially if SAFE used stuff can be had cheap.

Personal note: the trucking industry in general is dying and super deals can be had on safe, good stuff at your local, friendly, heavy truck wrecking yard.  HB of CJ
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BUR
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« Reply #2 on: May 02, 2009, 09:16:45 PM »

I changed all of my 12-22.5s and went to 11-24.5s. I can see no problem with changing as long as the weight rating will handle your load. The benefit is that I can find 11-24.5s anywhere if I have a problem on the road.  BUR
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Sean
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« Reply #3 on: May 02, 2009, 11:10:35 PM »

Is there an echo in here?

I hear this all the time:  11r24.5 are cheaper and easier to find than 12r22.5.  Both true, however, I have studied the cost difference and the availability issue, and, frankly, most of us will not save enough over the lifetime of our buses to justify the expense of changing the wheels.

The short answer is, yes, you can change wheels.  Make sure you get the correct mounting (hub-pilot versus stud-pilot aka "Budd"), correct hub bore, and correct bolt holes for your application.  Then, make sure you recalibrate your speedometer, and, if DDEC-equipped, the DDEC RPM parameter.  Lastly, measure your wheel-by-wheel weights to get the correct load range and inflation for the new tires.

Remember that the 24.5 wheels will give a stiffer ride than the 22.5 wheels under all conditions.

I am not sure why you would want to run different size wheels on the steer axle vs. the rears, although this is common on very heavy coaches.

-Sean
http://OurOdyssey.BlogSpot.com

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belfert
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« Reply #4 on: May 03, 2009, 07:32:48 AM »

I think the only time switching from 12R22.5 to 11R24.5 might make sense is if one is switching to aluminum wheels.

My Dina has 11R24.5 tires, but the plate inside actually calls for some metric size.  Before I picked up my bus I called MCI to ask what size tires are on a Dina.  They said 11R22.5 or 12R22.5 (can't recall).  Obviously the tech support guy had no clue and gave the stock answer for tires on a real MCI.  (A lot of the tech support guys are pretty decent on the Dinas.)
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Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
RJ
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« Reply #5 on: May 03, 2009, 01:51:25 PM »



I think the only time switching from 12R22.5 to 11R24.5 might make sense is if one is switching to aluminum wheels.



Or, in the case of GMC V-drives, when installing a V-730 in place of the OEM 4-spd stick.  The taller 24.5s make up the difference the automatic's lower bevel gear ratio takes away.



HBofCJ -

EVERY tire is different.  Even 12R22.5s from the same manufacturer may have different revolutions per mile (equivalent of rolling diameter) - check any of the major's websites and you'll see.  Some "drive" tires turn different revs/mile than equal-sized "steer" or even "all-position" tires, so you gotta do your homework!


Busnut83) -

Whatever you do, just don't put a 12R22.5 on one side and an 11R24.5 on the other side on the same axle.  Doesn't matter on the tags, but don't do so on the front or drive axles.

FWIW & HTH. . .

 Wink
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RJ Long
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Fresno CA
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