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Author Topic: Tire size question  (Read 1839 times)
travelingfools
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« on: August 22, 2011, 07:29:32 PM »

Well, I'm finally in the market for new tires. my current size is 315R 80 x 22.5. My front tires are good, but all the rest are beginning to show wear, cracking etc. My plan was to move the front tires back, purchase some good used tires from a local truck salvage company for the drives and purchase two new steer tires.  In doing searches here, I'm beginning to think I should be switching to 12r 22.5. Would it be ok to put the 315's on the tag and 12R's on the drive and steers ? Any advantage to staying with the 315's ? My bus is an 87 MC9.
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John P, Lewiston NY   1987 MC 9 ...ex NJT
Melbo
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« Reply #1 on: August 22, 2011, 07:52:31 PM »

On my 8 I have 12R's on the steers and 11R's on the drives and tags --- Don't know if there is a problem with that but it has worked for me --- Might be better to have all the same size.

HTH

Melbo
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TomC
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« Reply #2 on: August 22, 2011, 09:29:53 PM »

Why don't you weigh your bus by axle.  You might be able to go to a 11R-22.5-which would be much less money then the 315/80R-22.5.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RJ
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« Reply #3 on: August 23, 2011, 12:47:29 AM »

John -

Be aware that the truck tire industry is in the middle of switching to metric-sizing for their tires, like the auto tire folk did several years ago.

Depending on the individual tire's revolutions per mile, you may find that a 315/80R22.5 is virtually identical to a 12R22.5.

A 295/80R22.5 may cross over to an 11R22.5.

So, a couple of things:

1. Weigh your coach, like Tom suggested.  That way you'll know what sort of load your tires will be supporting.

2.  Your MC-9 came from the factory with 12R22.5 tires.  Matching the revs per mile as close as possible with give you OEM performance.  MORE revs per mile = lower top speed and greater fuel consumption.  FEWER revs per mile creates the opposite.


Good luck, and do your homework!

FWIW & HTH. . .

 Wink
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luvrbus
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« Reply #4 on: August 23, 2011, 07:18:01 AM »

Giving up the 1 in in width going to a 11R sure changes the driving characteristic and ride on a MCI or a Eagle JMO stay with 12R not worth it to save a few bucks,that is probably why you have 315's on the front is to help with the road wander and they do help  

good luck
« Last Edit: August 23, 2011, 07:38:29 AM by luvrbus » Logged

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Sean
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« Reply #5 on: August 23, 2011, 07:31:24 AM »

... Would it be ok to put the 315's on the tag and 12R's on the drive and steers ?

The short answer to this is "Yes" and that's exactly what I would do.

Quote
Any advantage to staying with the 315's ?


No, unless your coach is very heavy.  The only advantage the 315s have over the 12R is they have a higher load limit.  Otherwise, they are more expensive, harder to find, and, on the front axle, make it harder to steer at low speeds.

Quote
... purchase some good used tires from a local truck salvage company for the drives


Make sure whatever you get for the drivers are a matched set.  If you have slightly different tires or tread depths on the inners and outers, you'll accelerate the wear greatly, and if you a slight difference from one side to the other, it will tend to push the coach to one side, accelerating wear on the steers as they compensate.

-Sean
http://OurOdyssey.BlogSpot.com
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travelingfools
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« Reply #6 on: August 23, 2011, 03:45:20 PM »

Thanks to all who replied.. Its greatly appreciated. Im going ahead with my plan of moving the 315's to the tag and using the 12R's on the rest. I got a call today from a friend who told me of a guy thats got 4 never mounted inside stored 12R's for 390 each. Prob gonna pull the trigger on them for the drives and look for a deal on two more for the steers.
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John P, Lewiston NY   1987 MC 9 ...ex NJT
usbusin
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« Reply #7 on: August 23, 2011, 04:53:20 PM »

John, make sure you check the DOT mfg. date!  How long have they been stored?
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Gary D

USBUSIN was our 1960 PD4104 for 16 years Ustruckin' is our 2001 Freightliner truck conversion
travelingfools
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« Reply #8 on: August 23, 2011, 04:57:09 PM »

John, make sure you check the DOT mfg. date!  How long have they been stored?
Hes telling me 3 years

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John P, Lewiston NY   1987 MC 9 ...ex NJT
usbusin
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« Reply #9 on: August 23, 2011, 06:07:25 PM »

I would still check the date.  The first two numbers are the week and the last two numbers are the year of mfg.
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Gary D

USBUSIN was our 1960 PD4104 for 16 years Ustruckin' is our 2001 Freightliner truck conversion
harley86
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« Reply #10 on: August 24, 2011, 04:47:35 AM »

Quick question about tires My 1977 Eagle came with 11R 24.5's when I purchased it  they had great tread however the DOT date was 1994 and they were starting to crack.
The Bus seemed to drive and ride really good. But the tires were making me very nervous.  I went out yesterday and spent a small fortune on brand new Michellens all the way around. My question is did my bus come with 11R 24.5 tires and should I have changed to 22.5's I know the 22.5's would have been about $50 cheaper per tire but I would have had to change out my aluminum wheels.

Thanks Kerry
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luvrbus
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« Reply #11 on: August 24, 2011, 06:54:01 AM »

Harley, if your Eagle is a Brownsville built Eagle you cannot run 22.5 with out a spacer the brake drums are to large the wheels hit drum look at your manufactures plate it will tell you what size the Eagle came with more than likely 24.4 with a GVW of 38,800 22.5 will be 40,000
 

good luck
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RoyJ
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« Reply #12 on: August 24, 2011, 12:10:58 PM »

Quick question about tires My 1977 Eagle came with 11R 24.5's when I purchased it  they had great tread however the DOT date was 1994 and they were starting to crack.
The Bus seemed to drive and ride really good. But the tires were making me very nervous.  I went out yesterday and spent a small fortune on brand new Michellens all the way around. My question is did my bus come with 11R 24.5 tires and should I have changed to 22.5's I know the 22.5's would have been about $50 cheaper per tire but I would have had to change out my aluminum wheels.

Thanks Kerry

IMHO, I'd stay with the 11R24.5s.

I just made the opposite change on my coach rear end, from 22.5 to 24.5. To get a tire in 22.5" that's similar in diameter (and therefore rev/mile) to an 11R24.5, you'll need a 12R22.5 or 315/80R22.5. Those tires are MUCH more expensive, and harder to find (especially on the side of the road) than 11R24.5, which is a relatively common truck tire.

If you go with the cheaper 11R22.5, you may run into load capacity issues with an Eagle. Also, you'll loose an inch of ground clearance on a coach that's pretty low to begin with.
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Jerry32
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« Reply #13 on: August 24, 2011, 12:49:30 PM »

Nobody seems to mention the larger tire on the drive axle will help you mileage.. I run 11R24.5 on the drive axle and get 7.5 MPG with 8v93 and auto trans.   Your coice though Jerry
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robertglines1
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« Reply #14 on: August 24, 2011, 12:56:33 PM »

Good point our buses were designed to carry allot more weight  passangers plus luggage than our conversions usually weigh so the taller tires would give us a more mileage friendly final gear ratio.   
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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