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Author Topic: Tire Talk  (Read 2709 times)
TomC
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« on: March 26, 2013, 08:36:05 AM »

Tires are talked about quite a bit since tires are a big expense, only second to fuel burned. Just to be curious, I went on the Michelin commercial tire site to see how many tires are made. Michelin makes 29 different steer tires (all position), 23 drive, and 13 trailer tires in various sizes. I looked up 11R-22.5 and found they make 5 different all position tires. If you have a 4spd manual, a 6-71, 8V-71 or 6V-92TA, you don't really have enough power to take advantage of drive tires-and drive tires are typically more noisy. If you have an engine with over 400hp and either an Allison or multi spd transmission, then a drive tire would work for you.
Just to give you an idea of the 5 tires I found:
-XZA-1 first generation over the road all position tire-good tire, cheaper then the next tire
-XZA3+ 3rd generation over the road all position tire that is fuel efficient. Great tire, but has thinner side walls that don't like to be banged against the curb or go over curbs.
-XZE2 regional tire that is rated to 75mph. This is the tire I use-has reinforced side walls, but won't get much more then 80,000 miles of life out of them. Most of us would run out of time before miles anyway.
-XZU3 regional transit bus tire-very strong sidewalls and can carry more weight then the normal 11-22.5. But only a 62mph rating.
-XZY3 aggressive tread on/off road tire with 65mph rating. Great for logging and dump truck.
My point-as I've said many times before-tires are much more then big round rubber things that support the bus. They are the only contact with the road for traction. Since most buses are underpowered, braking is the main concern. El cheapo Chinese and Russian tires look good on the outside, but who knows how they perform? You can bet that the name brand tires like B.F.Goodrich, Bridgestone, Firestone, Goodyear, Michelin,
Sumitomo, Yokohama, etc do extensive testing on their tires. Both brakes and tires are not areas to be cheap with.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Oonrahnjay
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« Reply #1 on: March 26, 2013, 02:13:21 PM »

  I went on the Michelin commercial tire site to see how many tires are made.

     Thanks, Tom, good data. 
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
6-cyl, 4-stroke, Leyland O-680 engine

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Dave5Cs
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1979 MCI MC5Cs 6V-71 644MT Allison, Roseville, CA




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« Reply #2 on: March 26, 2013, 02:27:55 PM »

Ok here we go. I have the 12R x22.5 and when I had my tires off the other day I noticed the wheel size was 8.25. Now on that size rim steel rims can I put 11R x 22.5  ?

Dave5Cs
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Ed Hackenbruch
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« Reply #3 on: March 26, 2013, 05:46:06 PM »

Yes you can. Smiley
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1968 MCI 5A with 8V71 and Allison MT644 transmission.  Western USA
TomC
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« Reply #4 on: March 26, 2013, 10:05:27 PM »

If you can run 11R-22.5's rather then 12R-22.5's you'll find the availability far better on the road, since it is still a very popular truck tire. And keep in mind they make both 14 ply and 16 ply ratings. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RJ
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« Reply #5 on: March 27, 2013, 12:14:55 AM »

If you have a 4spd manual, a 6-71, 8V-71 or 6V-92TA, you don't really have enough power to take advantage of drive tires. . .

Tom -

You've got to be kidding!

I just picked a random Michelin drive tire, the XDA3.  I notice that in the 11R22.5 size, that tire turns 495 revs per mile.

That's exactly the same tire revs per mile that thousands of GMC V-drive coaches had their powertrains developed around!

Granted, they weren't BMWs, but just like the Hare, they got you there.

So I'm having trouble understanding your thought process that a 2-stroke cannot handle "drive axle" tires.  Can you please elaborate?

FWIW & HTH. . .

 Wink
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RJ Long
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Hard Headed Ken
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« Reply #6 on: March 27, 2013, 04:12:28 AM »

Tom,
 What's your opinion on a safe tire age, 5 years, 7 years or 10 years??

Thanks,
Ken
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« Reply #7 on: March 27, 2013, 05:02:02 AM »

There is always a lot of talk about tire RPM and the manufacturer's stated specs.  The correct way to discern  this is on a smooth level floor.  Make a mark on the tire and floor and roll the coach one full rev, measure and then do the math from a speedo chart.  When the tires are hot they also grow a little also, and change the rpm somewhat.  In calculating the RPM for the VSS on my Silverside we used the above procedure and came up with 497, even though the tire mfg. stated 504. 
JFYI.

Mark
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TomC
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« Reply #8 on: March 27, 2013, 08:00:57 AM »

RJ-How're Doin? I said that the lower horsepower buses won't be able to take advantage of a drive tire-not that they can't handle a drive tire. With the lower horsepower, it is just plainly hard to spin the tires-unless you're in really slippery clay type mud. Then-how often does that happen? Also with snow-if it gets to that point that your drive tires are spinning, you should either have chains on, or my choice just plainly be parked. You can run drive tires on your bus if you want-it won't hurt anything. But-an all position tire will get better fuel mileage-less rolling resistance.

As far as tire life-it really depends on where you park the bus. If you're parked outside in a hot desert region with the sun hitting the tires, 7 years would be it. If you park indoors in mild climate 10 years or more would be it. The bottom line is to inspect the tires for bulges and cracking sidewalls. The tires have a hard job to do. Make sure the tires are up to the task with proper inflation (should use a system like PressurePro to keep track of tire pressure while driving). My first set of tires I went 14 years. I replaced them when I started to see sidewall cracking. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Hard Headed Ken
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« Reply #9 on: March 27, 2013, 08:39:07 AM »

Tom,
 You mentioned pressure sensors. I recently purchased several late model Alcoa wheels. Some of the wheels have pressure sensors inside the wheel that are part of the valve stem assembly, a bigger version of the ones that are installed in automotive wheels that have the pressure monitoring system from the factory. I think the wheels I have came from an MCI. Are some of the late models coaches equipped with TPMS from the factory now?

Thanks,
Ken
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TomC
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« Reply #10 on: March 27, 2013, 11:23:46 AM »

I can't speak for MCI, but I know Freightliner trucks the TPMS is still an option. This is sort of weird to me since cars have had them standard for several years now and truck tire pressures are more critical then cars. Do figure? Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
luvrbus
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« Reply #11 on: March 27, 2013, 11:39:04 AM »

MCI uses the Smartwave system TPM by Bendix fwiw
« Last Edit: March 27, 2013, 01:24:59 PM by luvrbus » Logged

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chessie4905
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« Reply #12 on: March 27, 2013, 02:22:08 PM »

maybe the revs per mile is derived from taking the average between full tread and worn/discard tread.
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« Reply #13 on: March 27, 2013, 08:47:32 PM »

SAE paper J1025 explains how tire rpm is determined.
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Jim Keefauver/1985 Wanderlodge PT36/6V92TA/MT654CR/East Tn.
RJ
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« Reply #14 on: March 27, 2013, 09:21:18 PM »

If you have a 4spd manual, a 6-71, 8V-71 or 6V-92TA, you don't really have enough power to take advantage of drive tires. . .

I said that the lower horsepower buses won't be able to take advantage of a drive tire - not that they can't handle a drive tire. With the lower horsepower, it is just plainly hard to spin the tires - unless you're in really slippery clay type mud.

Tom -

I'm sorry, my friend, but I'm still not getting your point.  What's the "advantage" to a drive tire you're talking about?  Why would you want to spin the tires anyway, as mentioned in your response?  To dig yourself in deeper?

FWIW & HTH. . .

 Huh
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RJ Long
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