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Author Topic: 12R 22.5 or 11R 24.5  (Read 10833 times)
jjrbus
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« on: March 17, 2007, 03:14:05 PM »

 I'm sitting on the fence on this. I've researched the archives. Cant see any reason I should put the same tire on my MCI5C that people are putting on 40,50,60 thousand pound buses. That are 40/45 feet long.
 The first response I come up with is to go by da book. Use what was spec'ed for the bus. Well da book says 11.50X20 or 12.50X22.5 are they even available anymore?
 I've visited several tire sites and the 11R 24.5 14 or 16 ply tires are rated for more weight than the front of my bus.  11,060 lbs front axle, bus fully loaded. rear is 18,620 total is 29,680.
 The minimum 14 ply I find is rated at 6045 lbs single. and 16 plys are rated at min 6610 lbs If I buy the lowest rated tire I would have a total of 12,090 pounds. That is 1030 pounds over my front axle wieght. and that is the worst I can do.
 My current tires, Michlen XZE 12R 22.5 are 486 rpm the 24.5 are 480. I know this will change my speedometer reading, but I have a new one sitting in a box, it has the dip switches.
 Am I missing anything here? Replys, opinions are always appreciated.
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tekebird
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« Reply #1 on: March 17, 2007, 03:39:41 PM »

OMG the can of worms you opened!

I vot 12r22.5........it is after all a bus tire.

they ride better than an 11x24.5
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« Reply #2 on: March 17, 2007, 04:12:09 PM »

JJR, I'm in the same boat (so to speak) for my 4107.  You might check out the discussion of "Wheel Width" now on page 2, as some of the folks responded to my fence sitting - and my asking about another option, 11R 22.5's.

Arthur
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Arthur Gaudet    Carrollton (Dallas area) Texas 
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« Reply #3 on: March 17, 2007, 04:29:53 PM »

JJ, I don't have a real background into why busses used 1200 rubber and 16 plys. I know the 1200 puts an extra inch between the wheel and the ground and that is why 1200/22.5 and 11/24.5 turn aprox. the same revs per mile. We pay Fed Excise tax on tires by the lb. That adds to the cost, 1200s weigh more and are also becoming rare. I suppose 1200 may give a slightly better ride, but thats a guess. I have not blown a steer tire on a bus but have blown one in a truck. When that 1100 blew (it seems like yesterday but wasn't) I thought that the wheel had left the truck, because it dropped so far to the wheel edge (maybe 11 inches)? Thats the scary part, and when you as a driver have to make good decisions. The first instict is to grab a lot of brake, but really you want to grab some throttle and let it settle down and then use a little brake to stop ,so you don't turn it sideways. I have circle track experience and have blown many steer tires on the track and always thought I was prepared for a truck tire blowout on the steer axle. I'm sure the experience helped me, but the racecar tire would drop about 4 inches and the truck tire dropped almost a foot. To give you an idea what you are going to be dealing with if you blow a steer on the bus, remove the right front tire and wheel, demount the tire and replace the wheel without the tire on the bus and take the jack out. INTERESTING HUH. Thats what you could be driving at freeway speeds! Does the wheel even lift the bus high enough to keep the right front corner from dragging the ground? If you have 1200 tires, it is going to drop 1 more inch farther, 12 inches, and the inch factor and the pucker factor are related in my opinion. So if you replaced the 1200/22.5 with 1100/24.5 you would gain 1 inch of steel wheel between the front corner of your coach and the ground if you blew that tire, and reduce possible damage as well as a few heart beats less sheer terror, since it would not drop as far. I have practiced the blown steer tire senario with my wife when she is driving. I yell BOOM in her ear, (she loves me) and she now knows to lock both hands on the steering wheel, straight ahead and to keep the throttle on until things settle, then ease off the road without heavy braking.
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« Reply #4 on: March 17, 2007, 06:32:26 PM »

Jim, I am going to 24.5 to help my rpms.  And also easier to find, but just an idea. Is your bus a Saudia bus? My 5 came from Az an they said they sold others, so I wonder if I will find some one who has one.  Thanks  Tom Y 
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Tom Yaegle
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« Reply #5 on: March 17, 2007, 06:53:16 PM »

Yup, its a Saudi! Rumored to be Osama's personal ride.  In the water fill door there is a sticker in Arabic! I bought the bus in Washington state.
 The taller tire for higher speed does not make sense when looking at tire websites. A 12r 22.5 has an rpm of (depending on manufacturer) 480rpm an 11R 24.5 has an rpm of 483. Unless you are looking at 12R 22.5 vs 12R 24.5, I did not research that.
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busnut104
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« Reply #6 on: March 17, 2007, 07:10:55 PM »

When I bought my coach it had 11R x24.5 on the rear and 12R 22.5 on the front, I made the change so I would have all the same tire all around and  went with the 11R x 24.5  16ply.  This is on a mc8.
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ChuckMC8
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« Reply #7 on: March 17, 2007, 07:36:57 PM »

I've had 12R 22.5" and now have 11R 24.5" and I can't tell any difference in the ride. I did have all my tires balanced.
  I changed for the availability of Alcoa's in 24.5 are much easier to find(and cheaper) than in 22.5"
I paid $100 each for freshly polished (used) Alcoas. (and I was able to inspect each wheel b4 I paid)
   I also paid $100 each for Goodyear takeoffs.
 I would just as soon have the 22.5" if they were the same deal-HTH Chuck
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« Reply #8 on: March 17, 2007, 11:49:46 PM »

NJT5573 stated that with a 12" tire you have 12" to go to the rim.  That isn't quite true.  All tires have an aspect ratio- like a 65 series or a 75 series, etc.  That is the percentage of height to the overall width of the tire (listed tire width is the overall width of the tire carcass, not the tread).  So for instance, on a 11R-24.5 by NJT's theory, that sidewall should be 11" tall.  Multiply that by two side walls (top and bottom of the tire), and you get 22".  Add 24.5" of rim and you should have a 46.5" diameter tire.  Not true!  The tires on my bus are Michelin 11R-24.5 16 ply that are 43.5" in diameter, not 46.5".  So my tire has an aspect ratio of 86.3%.  To figure diameter of a tire, take the width-11" multiply by the aspect ratio, which in this case is .863 you get 9.493.  Multiply that by two for the top and bottom of the tire and you get 18.986.  Add the 24.5" rim onto that and you get a tire that is 43.486" in diameter, or very close to the advertised 43.5".  What's more interesting is that the loaded radius (measured from the ground to the middle of the axle) is 20.3", because of compression from the weight of the vehicle.  The 11R-24.5 16ply makes 478 revs per mile, the 12R-22.5 makes 487 revs per mile (according to Michelin).  After being on the road for 21 years, I can tell you that the 12R is much harder to find than the 11R-24.5 on the road.  My tires ride very well, so much so that the first mechanic that worked on it really noticed a difference when the 12R's were taken off and he took it for a drive with the 11R's on.  The most important factor to a good riding tire is the proper tire inflation (my soap box).  Always go with the best tire (translated Michelin).  Good Luck, TomC
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« Reply #9 on: March 18, 2007, 11:44:17 AM »

Tom, thanks for cleaning that up for me. I knew I was off a little and used the ? to show that. This all seems academic to me in a way since as far as I have been down the bus road is with my 77 and 89 Eagles. They both had factory 11R24.5 rubber when I purchased them. I am thankful for that because its a common size in todays world. There are many good brands to choose from with nationwide availability. I have a war memorial in my neighborhood dedicated to the 15 soldiers that died in WW1 from my County in Washington State. These men were between 17 and 23 years old and all died in France. My father also fought to protect France in WW2.(Normandy Beach). I can't tell you one thing France has done for my country. I never pass up an opportunity to piss on a Michelin so keep the tire shine handy!
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"Ammo Warrior" Keepers Of The Peace, Creators Of Destruction.
Gold is the money of Kings, Silver is the money of Gentlemen, Barter is the money of Peasants, Debt is the money of Slaves.

$1M in $1000 bills = 8 inches high.
$1B in $1000 bills = 800 feet high.
$1T in $1000 bills = 142 miles high
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« Reply #10 on: March 18, 2007, 12:05:59 PM »

NJT, how do you know if the buses had factory 11-24.5's?

Although it is possible they were ordered this way.....or more than likely they were put on at delivery as tires were optional equipment........I doubt the 77 has 11's

a  final delivery record would be the only way to determine this.
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boogiethecat
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« Reply #11 on: March 18, 2007, 12:06:50 PM »

I've been having the same quandry.  Back a few years ago I found a football sized sidewall bubble one of my 12R22.5 Michelins on the rear.
So I pulled into the local Rip (off) Griffin truckstop and all they had in stock was some 11R22.5 steer tires, Michelin  XZA3's.
  After considerable thinking, and considering that All 6 tires were the same, I finally had them take my two front tires off and stick them on the rear, and then install the new 11R22.5's on the front.  This meant that the bus is now an inch lower in the front, but it also meant I could get back on the road instead of waiting days to get the proper tires in, and I was on a tight schedule.

The most amazing thing was how QUIET the bus suddenly was!!  My wife and I noticed immediately and were VERY impressed.

Here it is a few years later now, I've just stuck the Telma and new axle into the rear of the bus, and had the tired old springs re-arcd.  Now the bus looks like some kind of a low rider being that the front springs are still tired and the tires are too small.  It's ars is way up in the air and the front is sniffing the ground!!  I  So I figured I could put the two 11R22.5's  onto my bluebird which has 11R22.5's all the way around  anyway (and kinda needs a couple new ones on the front) and get some 12R's up there on the Crown, but I find that the only one Michelin makes in the XZA3 series is an 11R24.5.  Being that they are SOOOOO quiet, I really wanted to get XZA3's...

So considering this thread, it looks as if my question is answered, the 11R24's are the way to go!!

Thanks guys!!
« Last Edit: March 18, 2007, 12:09:20 PM by boogiethecat » Logged

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Gary '79 5C
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« Reply #12 on: March 18, 2007, 05:29:29 PM »

Thanks all for the info, I am set to go to a distributor for new steers this week and I have been cruising the info on tires.
I have a 5C Saudi with 24.5 Alcoa's. Think I will stick with the 11R for all said reasons.
BTW, In addition to the Arabic sticker on the Radiator fill door, mine has the "shadow" of the orig. Arabic GreyHound sticker in the SS just in front of the curb side rear tire well. You can see the slightest contrast revealing this. A friend who's native language is Arabic, translated. This Saudi came from St. Louis area. I was told that many came thru Nimco at the port of entry. Not sure how they were redeployed thru out the US.
Gary
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jjrbus
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« Reply #13 on: March 18, 2007, 05:36:06 PM »

10 of them are in a junk yard outside Buffalo NY. Which tires are you looking at for what price?
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luvrbus
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« Reply #14 on: March 18, 2007, 06:46:38 PM »

i have never had a problem finding 12R/22.5 any place in the west all the log trucks run the 12R /22.5  on the front that i saw at southern oregon diesel i replace my tires every 4 years now and haven't had to shop for tires.we have a great dealer in les schwab tire  no hidden fees and credit for your old tires
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