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Author Topic: changing 22.5 to 24 wheels  (Read 3887 times)
Danny
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« on: November 02, 2007, 05:50:48 AM »

I need new tires.  A truck driver friend of mine said I could change my 22.5 wheels to 24 inch rims on my MCI 102A3.  What do you guys think about this?  Any concerns?  The tire place asked if I would be having high or low profile tires... What's the difference for my application?

Thanks,
Danny
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zimtok
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« Reply #1 on: November 02, 2007, 06:04:06 AM »

I'm sure someone will be able to do the math for you, but changing tire size and/or high/low profile will throw off your speedometer and will increase/decrease your MPG.

A smaller diameter tire will rotate more times per mile then a larger diameter tire.


.
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« Reply #2 on: November 02, 2007, 07:09:56 AM »

A standard 22.5 tire has the same rolling diameter as the 24 low pro, there are pros and cons to each.>>>Dan
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jjrbus
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« Reply #3 on: November 02, 2007, 08:11:18 AM »

Go to the manufacturers website of the tires you want. Here is one for firestones   http://www.firestonetrucktires.com/us_eng/home/index.asp   You will find information on tire size, plys, load ratings, diamater ect you can compare dimensions. the outside dia or RPM between a 22.5 and a 24 may be negligeable depending on the manufacturer.
 At these sites you will also find load and inflation tables, after weighing your bus you will know how much psi to use for your bus!
 After doing some reasearch I put 24's on my 5C. HTH Jim
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TomC
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« Reply #4 on: November 02, 2007, 09:13:54 AM »

22.5" wheels are the vast majority of wheels used in the world.  24.5" is primarily a United States usage.  The standard size that everyone thinks of is a 11R-22.5 that is a 500rpm tire.  Now most all trucks are being equipped with standard low profile 22.5 that are either 275/80R-22.5 (Michelin's size) or 295/75R-22.5 (everyone else's size) at 517rpm.  Going to a standard low profile 24.5 which is the 285/75R-24.5 (275/80R-24.5 on Michelin) you are still at the same basic tire size as the 11R-22.5 at 500rpm.  If you go to the metric version of the 12R-22.5 which is the 315/80R-22.5, you can run the tire on a 8.25" wide rim, with a 9.00" rim preferred, and you'll get 487 rpm.  The biggest tire you can get for highway use (translated a 75mph tire) is the 11R-24.5, of which I am running at 476rpm.

For most of us with buses, the 315/80R-22.5, 12R-22.5 is just plainly too much tire for what we are carrying.  My complete bus weighs in at 10,500lb front and 20,500lb rear, so my 16 ply 11R-24.5 tires are an over kill considering they can carry over 14,000lb front and 26,400lb rear.  But, then I can run them at 90psi and get a nice ride.

My suggestion- run the 11R-22.5-if you want a little better carrying capability, then get the 16 ply version.  Those are rated at 13,200lb front and 24,000 rear.  Good Luck, TomC
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« Reply #5 on: November 02, 2007, 09:38:53 AM »

http://www.busconversions.com/bbs/index.php?topic=3621.msg33929#msg33929
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The manufacturer's tag in my bus has both sizes on it, here's a picture. Grin
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« Reply #6 on: November 02, 2007, 11:32:19 AM »

I changed to 24.5's on the rear only about 10 years ago.  The tires are cheaper, easier to find deals on, and I bought the "tallest tire " possible" and I go way faster. About 9 mph over the 22.5's that I took off.   Someone told me that I would really notice the difference when climbing hills but that is not true.  For everyday hillclimbing I cannot tell the difference and I have been a charter/entertainment  bus driver for 31 years. Our band bus travels up and down the west coast, Seattle to LA, and Vegas with NO problems.  This was way easier than putting in an overdirve tranny.
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« Reply #7 on: November 02, 2007, 01:36:39 PM »

Yeah again, too many different factors to consider.  In my particular case (1974 Crown ex-school bus) going to the tallest tire available gives the coach an additional one or soosss inch of ground clearance which may be very important.  The mill is in the middle of the bus laid on its side with very little ground clearance.  One inch difference in clearance may avoid that big (and $expensive$?) road debris.

Crown designed the bus with very large, oversize wheel wells sosss tire chains could be mounted without the fear of hitting anything. She has the standard 12Rx22.5 16 ply size on 9 inch wide 2-hole steel Bud type wheels,  which as someone already said, is really overkill for a bus.  But then again, the bus does have the 16,000 front axle and 34,000 pounds drivers, with a gvwr of 47,000+.  Wow.  Smiley Smiley Smiley
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TomC
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« Reply #8 on: November 02, 2007, 03:28:38 PM »

47,000gvw minus a 34,000 pound rear translates to a 13,000lb front end-which is more like it.  TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #9 on: November 05, 2007, 03:33:51 PM »

TomC has it exactly correct.  What is the point of having such a heavy front end?  I dunno.  But, that is what I have and with the 12RX22.5 16 ply Firestones (new) I can go to about 14000 or soosss on the front end.  Right now stripped, she goes right at 10,800 on the front.  Crown Coach Corporation did some strange things years ago. (went $broke$ in '91)  Maybe they wanted the entire football team sitting way in the...front of the bus.  The turning circle is amazing.  "HARD-A-PORT"!!!!  Smiley Smiley Smiley
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