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Author Topic: tire size / inquiring mind wants to know...  (Read 3327 times)
coolbus
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« on: June 17, 2007, 10:15:22 PM »

My bus (Prevost Champion) has 11R 22.5 tires up front,  as well as on the rear duals. The tags, however, are 10R 22.5  I had a blow out last week, and found that the spare tire (11R 22.5) would NOT fit the tag position. Serious clearance / rubbing problem.  Angry

Is it possible that the previous owner changed out all the 10R size for 11R, but left the tags alone? Did my bus come with 10R size tires all the  way around?  Huh

It doesn't make cense to have two sizes on tires on one bus. I called Prevost Car in Quebec, they thought all the tires should be the same size; couldn't say what that should be.  Undecided

Any other Champion owners have any thoughts? (The bus is 35' long, if it matters)  Smiley

thanks for your input!

Mark

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Busted Knuckle
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« Reply #1 on: June 17, 2007, 11:02:13 PM »

First of all Mark, yes all the tires should be the same size! That said I'd first check the Manufactures VIN plate. It should give you the weight capacities per axle & gross, it should also list the tire sizes & pressures per axle, as well as the VIN & Date of MFG. FWIW BK  Grin
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Jerry32
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« Reply #2 on: June 18, 2007, 02:22:43 AM »

Yes the vin plate has all the specifics on it and will tell you what tires were really supposed to be on your bus. souds like someone changed from the original.  Jerry
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RJ
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« Reply #3 on: June 18, 2007, 07:57:05 AM »

Mark -

Never heard of a 35-foot, three-axle Prevost Champion, and that's after 25+ years in the bus industry.

Prevost did make some 35-foot coaches, but they were all two-axle models.

The only coach I ever heard of having different sized tires on it OEM was the MCI MC-6 - tags were smaller than front/drive axle.

If the 11R-22.5s don't fit the tag, I'd suspect something to do with the wheel offset or width.  Try a different wheel and see what happens.

FWIW & HTH. . .

 Wink
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RJ Long
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coolbus
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« Reply #4 on: June 18, 2007, 08:33:49 AM »

The clearance problem is with the height of the11R tires. It literally rubs on a frame member near the top of the tire. Also, there is no wheel hump (wheel well) for the tags. but there is for the drive axel. Seems like if they were meant for the same size tires, they would have made wheel wells for the tags as well.  Huh

The bus is definately a 3 axel, 35 footer!  Smiley

maybe I can get rid of the tag axel @$#'y altogether?

thanks

Mark
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Hartley
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« Reply #5 on: June 18, 2007, 09:00:57 AM »

Sounds like that was a custom setup and maybe was a special order for a special application
like a weight limited roadway or cargo hauler.

The mystery is the 35 foot part. It is an odd setup, Prevost usually didn't build a 35 with 3 axles
from what I can tell. But stranger things have been built. It is odd that there is no clearance for the tag axle and tire combo.. That is truly a mystery.

Or, It was a shortend bus?

Dunno on that one....

How about 12R22.5's on the steer and drives and 11R22.5 on the tags? sounds more like it?
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TomC
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« Reply #6 on: June 18, 2007, 09:17:56 AM »

Personally-I would do what you said to do-mainly get rid of the tag axle.  I know that from a stripped out bus to a finished bus with all my junk it including my wife and I with full tanks, only added 3,000lbs to the bus.  I weigh in at 31,000lb and have a 36,000lb gvw, and that's a 40ft'r with 2 axles.  Course my transit does have larger brakes than highway buses-and that's the only negative I could think of-loosing some braking power and maybe a bit of handling stability.  But the tag axle weighs close to a ton, and then that freed up area where the tag was could be enclosed for additional storage!  I know of no other 35ft'r that has 3 axles, except for yours.

As to your tire problem, 10R-22.5 is a little used size of tire.  So if you get a blow out on the road, you'll be hunting alot for that tire.  I would suggest you go with the low profile 295/70R-22.5 that is pretty much the standard of the trucking industry now.  It'll be just about the same diameter at the 10R, and easily replacable if needed.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #7 on: June 18, 2007, 09:28:06 AM »

Bus was probably built for the norther tier of Canada where the roads are not that good and you have some Permafrost issues.

the extra axle would distribute the weight better.

Flx made some clippers with a tag axle for this situation.

RJ, The 40 foot Buffs with the bogie had a smaller tire as well
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Don4107
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« Reply #8 on: June 18, 2007, 09:54:42 AM »

Sounds like an interesting coach.  Do you know what it weighs? 
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Don 4107 Eastern Washington
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coolbus
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« Reply #9 on: June 18, 2007, 10:39:49 AM »

good question, as to the weight. I just got it home, havent had the chance to weigh it yet, but will do so soon. It is already converted, so the only variable will be the holding tanks, luggage, etc.

thanks

Mark
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Dreamscape
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« Reply #10 on: June 18, 2007, 12:07:58 PM »

How about a picture?
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Stan
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« Reply #11 on: June 18, 2007, 12:15:40 PM »

Just out of curiosity, what is the wheelbase of your 35' Prevost, measured from center of front wheel to center of drive wheel?  Are the tag wheels beside the engine or in front of the engine? As others have said, this is a very unusual bus so there are lots of questions. Since you say that Prevost could not answer your question, this may be a modification done after the bus left the factory.
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coolbus
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« Reply #12 on: June 18, 2007, 02:14:03 PM »

I just measured...

19 feet, 10 1/2 inches center to center.

I will try to post the only picture I have...

thanks

Mark
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Stan
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« Reply #13 on: June 18, 2007, 02:30:17 PM »

coolbus: Yes indeed, you have one cool bus. That 238" wheelbase is pretty much the norm for a 35' T drive with the drive axle as far to the rear as possible. That means the tag wheels have to sit beside the engine which is what appears in your picture. At least you have the option of putting in a 12V71 without having too much overhanging weight!!
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Don4107
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« Reply #14 on: June 18, 2007, 03:22:22 PM »

Very nice!  If you stay with the 10 hundred tires be sure to check the date codes on the replacements.  Since they are not very common they could be old stock and not something you want to use.

Good Luck.
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Don 4107 Eastern Washington
1975 MCI 5B
1966 GM PD 4107 for sale
1968 GMC Carpenter
coolbus
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« Reply #15 on: June 18, 2007, 09:45:50 PM »

okay, here's what the VIN plate says:

FRONT~   13,000lbs           Tires~   12R22.5         Wheels~   22.5X8.25

DRIVE~      22,000lbs          Tires~   12R22.5         Wheels~   22.5X8.25

AUX~       10,000Lbs          Tires~   12R22.5          Wheels~   22.5X8.25

My question:

Is a 12R 22.5 tire (as spec'd on VIN plate) shorter than a 11R 22.5?  Huh The 11R is definately too tall; rubs on the tag position.

The design of the bus makes it look as though the tag should be a shorter tire, since there is no wheel well inside the bus above the tag like there is on the drive axel & front axel. However, the VIN plate does show same size tires all the way around. Maybe less wheel travel on the tags?

This is a puzzle for me; I don't understand these tire sizes. Is it possible that the PO put on different (taller) tires so as to change gear rato?

Again, the bus currently has 11R 22.5 tires on front & drive axel; the tags are 10R 22.5. If I put a 11R 22.5 tire on the tag position, there is serious clearance issues with the height of the tire. Is a 12R the same height as a 10R? Seems odd to me.

thanks

Mark
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tekebird
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« Reply #16 on: June 18, 2007, 10:13:27 PM »

12r is a "standard" bus tire size

good chance some bright individual was screwing with your ride ht...trying to make it perform/handle better....LOL

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TomC
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« Reply #17 on: June 18, 2007, 10:37:02 PM »

The 12 will be taller than the 11 which is taller than the 10.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #18 on: June 18, 2007, 10:44:54 PM »

Mark ... maybe the rear ride height is not set up high enough. If you look at my bus it isn't running flat, the rear is sitting a little higher than the front of the bus in a nose down attitude. Does you bus have a wheels-up air switch by the brake switch?  Most Prevost tag can be lifted.

Ron
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Stan
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« Reply #19 on: June 19, 2007, 05:20:56 AM »

Your bus gets more unusual with every post. I don't think it is possible to have no wheelwells  on your bus and get full suspension travel. Is it possible that the previous owner removed the wheelwells? Another strange thing is the weight distribution from your VIN plate. As a normal rule, tag axles with a single tire only carry 30% of the drive axle weight. With tires two sizes smaller than spec, you will have to reduce the weight on the tags to about 4000# by reducing the pressure in the tag air bags.
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TomC
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« Reply #20 on: June 19, 2007, 06:45:15 AM »

You could go as small as a 265/75R-22.5 and still have sufficient tire to take the rated 10,000lb load rating of the tag axle. As to tire size, the only reason that 12R's were originally used, was they were the only tire that could take that kind of loading-realizing that tires when the bus was built were still nylon bias ply tires.  Now with the excellent steel radials, you can go smaller and not have to worry about loading.  At 13,000lb you could use either a 11R or 295/75R-22.5 16 ply for the front.  For the rear at 22,000lb, a normal 11R or 295/75R-22.5 at 14 ply would be enough.  Most converters will not come close to the gvw rating for passenger carrying capacity.  For instance, my bus is rated at 13,000lbs front and 23,000lbs rear.  I went to 11R-24.5's that are 16 ply since they will take that amount.  At full pressure, the 16 ply tires will take 14,000lbs front and 26,300lbs rear.  With only 10,500lbs front and 20,500lbs rear, I run 90psi all around, and that is even a bit high.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Hartley
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« Reply #21 on: June 19, 2007, 07:02:01 AM »

It occurred to me that there might be an error in the description of tire clearance.

When you say the tag hits the support. Is that with the bus up and running with the suspension aired up or when it is sitting with no air pressure?

Generally speaking many buses when they have no air in the suspension will sit all the way
down to the stops which usually are barely high enough to keep from touching stuff.

My RTS sat really low and if I didn't have the wheels straight the front tires would bend the wheel well rubber trim, My MC9 does the same thing without air. My tags look like they would almost touch without air pressure but with full pressure they have 7 inches of clearance. These things have a lot of travel.

There can be from 3 inches to 14 inches of clearance depending on what bus and suspension settings.

From the picture you posted it looks like someone has lowered the ride level or there was no air pressure to hold the bus up. In that case this whole issue can be misleading and what people will tell you may not be the exact answer.

Air it up and check the clearances, Then let us know what you find. Anything else is conjecture.

Dave....
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coolbus
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« Reply #22 on: June 20, 2007, 10:37:51 PM »

This is what happens when the WRONG size tire is used in the tag position...
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coolbus
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« Reply #23 on: June 20, 2007, 10:45:29 PM »

Check out all the shredded rubber! The tire was rubbing on the airbag, as well as the steel structure mounting the airbag. The tire was rubbing so bad. it rubbed thru within two - three blocks after mounting it up!  The top of the tire was also rubbing, but no damage occured as a result.

The tire I used was a 11.00 R 20.  I thought they were the same diameter as a 11.00 R 22.5?  My mistake.

Now to replace an otherwise perfectly good airbag... and find a couple good tag tires...

Mark
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TomC
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« Reply #24 on: June 21, 2007, 12:16:15 AM »

11.00R-20 = 12R-22.5.  10.00R-20 = 11R-22.5.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #25 on: June 21, 2007, 01:00:46 AM »

Maybe you have the wrong rims on the tags.

The offset is wrong.Huh?

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