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Author Topic: 11R 22.5 tires to replace 12R 22.5's??? Should I?  (Read 10430 times)
Michael Mc
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'72 MCI MC5B Challenger




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« on: June 23, 2010, 12:05:06 PM »

OK,  first off - I don't know diddly about tires for busses.  I have a MCI5 and it's due for tires.  I call the first guy and tell him that I have 12R 22.5 Goodyear G159 tires and I need a quote on 6.  He says he will call me back with the quote.  In the mean time, I call the second guy.  He says that I should change to 11R 22.5's in a Toyo tire.  He sells me on the idea that they are a more popular size (again, I don't know) and if I need one on the road, I could find one more easily.  Also he says the only difference is that they are narrower.  I asked about load rating.  His answer - "he puts them on big trucks all day long".  His price on those is $359 each "out the door".  Great, until the first guy calls back with his quote.  $3,446.65 for six " out the door" and he has to order them.  I asked if I should go with a more popular tire (see, I learned from the first guy  Smiley ) like the 11R 22.5.  His answer - that's a big ole bus, the 12R 22.5 is the only size that I can put back on it.

Who is right?  I don't mind paying a little more for the correct tire.  Safety is more of a concern to me than the money.  But, if I cut a tire on the road, the first guy is right ( I guess ).  Maybe I would have better luck finding a more popular size?? like the 11R 22.5.  What should I do?

Help,
Mike
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luvrbus
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« Reply #1 on: June 23, 2010, 12:45:19 PM »

The 12r22.5 is a bus tire big difference between the 12r and 11r tire 12 r's are wider and taller plus carry more weight


good luck
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Michael Mc
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'72 MCI MC5B Challenger




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« Reply #2 on: June 23, 2010, 12:56:19 PM »

Thanks luvrbus.  I knew that there was a reason that size was on the bus.  That's the direction that I was leaning, I just needed confirmation.  How true is it that I might have trouble buying 12R 22.5 tires in a "breakdown" situation?
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ccbmster
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« Reply #3 on: June 23, 2010, 01:02:23 PM »

I am no expert but over the past five years I have needed a tire (12r) while on the road three times and have never had to make more than a couple of phone calls to get one.  Oh and I am a cheap sob so I get used tires for everything but the stears.  Never had a problem getting new or used. 

I guess in some parts of the country it could be a bit of a problem but it seams I have never been too far from a charter bus company that can sell me a tire or tell me who to call.
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86 MCI 102A3  MI/CA with SoCal being primary. 6V92 with Allison 740 Auto
82 MCI 9 8V71N with Allison 740 Auto..soon to be parted out or scrapped
luvrbus
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« Reply #4 on: June 23, 2010, 01:03:35 PM »

Mike you are going to get all kinds of answers for that question the only thing I can tell you I ran 12r22.5 for over 20 years and never had a problem buying the 12r22.5 tire.
The guy that bought my bus is having new ones installed and didn't have trouble finding the tire and this guy lives in Battle Mountain Nev of all places




good luck
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bevans6
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« Reply #5 on: June 23, 2010, 01:12:56 PM »

An MCI 5 is not one of your heavier buses, so the 11R tire will be well within it's weight capacity.  My 5C drive tires are under the lowest weight in the Firestone load/PSI chart for the 12R-22.5's I have, which are H rated.  That load chart implies that the 11R-22.5 will need between 10 and 15 PSI more to carry the same load as a 12R-22.5, which will have an impact on ride quality and handling.  The size difference will have an impact on engine RPM, and hence top speed will suffer while acceleration will improve.  

There was a conversation a few weeks ago about using tires different from what is on the GVWR and axle rating placard.  The placard on my 5C doesn't list the tires I have, which are 12R-22.5 H rated, it only lists 12.00-22.5 G rated.  So neither the 12R or the 11R is on the placard.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
Michael Mc
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'72 MCI MC5B Challenger




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« Reply #6 on: June 23, 2010, 01:18:35 PM »

Brian (bevans6),
Curious - How much pressure do you run in your tires?  Also, where is this placard which you speak of?
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bevans6
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« Reply #7 on: June 23, 2010, 01:32:57 PM »

I run my rears at 80 psi, although the load table says I could go to 70PSI.  I run the fronts at 85PSI.  Here is  the load chart for my tires: http://www.trucktires.com/firestone/us_eng/load/load_pdf/F_loadTables.pdf   My tires are Firestone FS560plus, 12R-22.5 load range H.

Based on that I could have up to 11,380 lbs on the front axle and 20,760 on the rear axle.  I am closer to 10K on the front and 18K on the rear, or even under that.  Part of my thinking is that if my axles are lighter than the lightest weight in the load chart, it's just possible that I have more tire than I actually need...

The placard is rivited to the fiberglass cap above and slightly behind the driver.

We had a magnitude 6 eathquake here today and I missed it.  Dang!  epicenter about 250 miles away.

Brian 
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
viking42
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« Reply #8 on: June 23, 2010, 01:42:43 PM »

I have a 4106 871 w/730 auto transmission.  Went from 12/22/5 tires to 11/22/5 tires and it cost me 3/4 mile per gallon.  From 7 1/2 mpg to 6 3/4 mpg.
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Jerry32
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« Reply #9 on: June 23, 2010, 03:16:21 PM »

If at you want to change to 11R tire get some wheels used and use 24.5 and get better mileage  at lower RPM's Jerry
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1988 MCI 102A3 8V92TA 740
Ed Hackenbruch
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« Reply #10 on: June 23, 2010, 06:15:16 PM »

I have 11 r 22.5 tires on my 5A and have had no problems in 7 years, have plenty of load capacity that is not being used. You just need to look at the tires and your weights and see what load rating you need for your tires.  According to my book this came with 11.00 x 20 tires originally, wheel size was 20 x 8.  The new wheels that i bought this spring were 22.5 x 8.25 as were the old ones that i was replacing.
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
James77MCI8
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« Reply #11 on: June 23, 2010, 06:29:30 PM »

Ran 11R's on my 5 for 8 years with no problem. You will probably never reach the weights that the bus encountered while in revenue service.
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77 MCI 8
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Bill B /bus
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« Reply #12 on: June 23, 2010, 06:31:12 PM »

On the 4108 it came with 12R22.5 with the 4.12 rear gear. That put the top speed in excess of 90MPH at best guess of 2300RPM. I got tired of having to shift to 3rd of almost any hill, even in the northeast interstate corridor.
Changed to 11R22.5. Ride stayed the same even with more air pressure. Fuel mileage a little increase. Much better hill climbing. Top speed dropped to about 85-86 MPH. 3rd gear downshift used to be 62-63 MPH and that dropped to 57-58.
My buddy, 4104 with 112R24.5 top speed about 76MPH, always pulled away on the hills. After the change we were just about even in speed response on the hills.
That was my reasoning on the tire size change.

Bill
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Bill & Lynn
MCI102A3, Series 50 w/HT70
Ed Hackenbruch
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« Reply #13 on: June 23, 2010, 06:43:34 PM »

A friend just pulled into BUSN' with his 5A, i will check his tire size. I believe he has a stick, i have an auto, and my toad, we should be headed the same direction when we leave. Maybe we can have a bus race up I-5?  Grin
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
Ed Hackenbruch
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« Reply #14 on: June 23, 2010, 07:42:37 PM »

Yup, he has 11r22.5 tires on his too.  Looked in my parts book and it show the 22.5 x 8.25 wheel as the "heavy duty wheel" .  He also mentioned that the 5s also came with 10x20 tires too. I remember seeing that somewhere in one of my books but did not find it doing a quick look.
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
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