Tire size 900x20?

happycamperbrat · April 30, 2009, 07:32:59 PM

I am thinking about buying a cheap bus just to get the tires. I found this ad http://cgi.ebay.com/ebaymotors/1979-Wayne-International-65-Passenger-School-Bus_W0QQitemZ330326451792QQcmdZViewItemQQptZBuses?hash=item330326451792&_trksid=p4506.c0.m245&_trkparms=65%3A1%7C39%3A1%7C240%3A1318 and the tire size is 900x20 I have never heard of such a thing...... of course I am new to all this. But I have 12x22.5 and have read that there may be another number that would be the same as my tire, like a metric number. I dont know metrics, what size of tires should I be looking for? I am confused... as usual

rgrauto · April 30, 2009, 08:24:12 PM

Hello Happycamper, The 900x20 is older technology and not knowing what kind of bus you own they may not fit you bus. You say you have 1200x22.5 tires. It would be less expensive to use a 1100x22.5 tire. Most all trucking companies use 1100x22.5 tires, so if you shop around you might buy some good take off tires or retreads for rear without spending a lot of money because they are the most common tire. Hope this helps.
Glen

belfert · April 30, 2009, 08:30:14 PM

$700 for a bus with "usable condition" tires of a strange size is probably not a bargain.

Bus fleets tend to put the worst tires they have on a bus that is being sold. "Usable condition" could mean barely legal, but not quite bald.

gus · April 30, 2009, 08:49:47 PM

These are tube type tires and are probably mounted on two piece wheels, you don't want to mess with these.

It is basically the same size tire as 900 x 22.5 which is tubeless. This size is too small for the great majority of our buses.

Wheels can be changed from one vehicle to another if the lug pattern is correct but the tires can't be changed between the wheels.

Sean · May 01, 2009, 01:03:11 AM

Quote from: happycamperbrat on April 30, 2009, 07:32:59 PM
... But I have 12x22.5 and have read that there may be another number that would be the same as my tire, like a metric number. ...

You most likely have 22.5" diameter, 8.25" wide tubeless rims on 15° drop centers. This is a standard and very common wheel size.

The 12R22.5 tires fitted to your bus are rated at a certain load. While it is true that 11R22.5 tires will also fit those rims, as suggested by others, there are three potential problems with this:

11R22.5 tires have a much lower load capacity than 12R22.5 tires. Before you can change to this size, you will need to actually weigh each wheel position and ensure that the smaller tire can safely carry your load.
This tire is actually a smaller diameter. That means that your speedometer will be incorrect (reading too high) unless you recalibrate it, and your top speed will also be lower.
The smaller diameter can also impact ground clearance, which may or may not be a problem for your coach.

There is a metric "substitute" for the 11R22.5 size, which has all those same limitations. That size is 265/75R22.5.

There is also a "metric" tire that can substitute for the 12R22.5, which is the 315/80R22.5. This is, however, a much beefier tire, intended for heavier loads than the 12R22.5 can handle. It is much harder to find, much more expensive, and has higher Federal Excise Tax (FET) than the 12R22.5. Unless you have a real need for the load capacity, I would stay away from this size.

Bottom line, 12R22.5 is a very common size, and absent really good reasons to change, you are probably better off sticking with it. If you are trying to save money on tires, get a quality set of new steer tires from one of the less expensive brands, such as Firestone, and then ask around at your local truck tire dealers about take-offs for the other positions. Many dealers will have used take-offs with plenty of legal tread left for about $100 or so in that size, and there is no FET on used tires.

Lots of information on this topic in the archives as well.

-Sean
http://ourodyssey.blogspot.com

Dallas · May 01, 2009, 01:59:08 AM

Sean,

I think you'll find that the 11R22.5 size interchange is closer to 285/80R22.5 and the 12R22.5 is closer to the 305/80R22.5
315/80R22.5 which is standard on many buses is actually closer to 12.5R22.5
265/75R22.5 is a low profile tire equal to a 10.50R22.5

http://www.csgnetwork.com/tireinfo4calc.html

Singing Land Cruiser · May 01, 2009, 06:17:47 AM

I had a 1967 M35A2 Deuce & 1/2 that had that size tire on it. 10 new street tread cost $1,200 in 2007. I uesd it for parades. M&C

TomC · May 01, 2009, 07:49:18 AM

Any truck/bus tire with a whole number diameter-like 20" or 22" is a tubless tire. 900x20" translates to a 9" x 20"-much smaller then your 12"x22.5. Rim diameter dimensions with .5 in them are tubless-like 19.5, 22.5, 24.5. Don't buy a bus for their questionable tires.
Just a general comment-I get a bit miffed with the lax attitude that some have on the board about tires on the bus. Tires are much more then big round rubber things that hold air. Tires are the only contact you have with the road, the only means by which to control your bus, and to stop it safely. Michelin makes 45 different truck/bus model tires alone just for on and on/off highway use. Please do yourself a big favor and not be cheap about your tires-be cheap elsewhere. Buses are among the heaviest vehicles on the highway (actually are heavier then big rig trucks when you factor in that we are loaded all the time with less axles), put the biggest strain on tires-especially when maneuvering. Buy new tires that will give you many years of faithful, worry free service. Good Luck, TomC

Don Fairchild · May 01, 2009, 08:48:53 AM

Hey girl;

It was nice to have you come by the shop the other day. How did the ordeal come out with the rear brake.
I belive the tires On your RTS were 1200:22.5's Stay with them. You can look around at the tire shops and maybe find some good used tires that will get you by for a short time while you are getting used to driving the bigger bus.. If not save for new one and do it right the first time. takes a load off of the mind while on the road.

Hope this helps. come by and say hi next your in town.

Don

Sean · May 01, 2009, 08:54:23 AM

Quote from: Dallas on May 01, 2009, 01:59:08 AM
...
I think you'll find that the 11R22.5 size interchange is closer to 285/80R22.5 and the 12R22.5 is closer to the 305/80R22.5
315/80R22.5 which is standard on many buses is actually closer to 12.5R22.5

All true, Dallas, except that 285/80R22.5, 305/80R22.5, and 12.5R22.5 are not sizes that exist in the real world. I know you can special-order some of these sizes in certain places, but you would then likely be waiting weeks or months for the small-batch production run needed to make them.

Bridgestone, for example, which is one of the largest suppliers of heavy tires in the US, does not list any of those sizes in its catalog.

I was trying, in my discussion, to stick to items one might actually find at a tire dealer (or on an existing vehicle). FWIW.

I probably should also have mentioned the 295/80R22.5 as a possible substitute for the 11R22.5, although that tire is typically fitted to 9" rims rather than 8.25".

-Sean
http://ourodyssey.blogspot.com

TomC · May 01, 2009, 09:57:39 AM

I guess some are making up tire sizes. Looking in my Michelin book, I see a 275/80R-22.5 and the other manufacturers make the 295/75R-22.5-but no 285/80R-22.5-there is a 295/80R-22.5 though. In regional transit bus tires, there is a 305/70R-22.5, a 305/85R-22.5, but no 305/80R-22.5. Also, 315 converts almost exactly to 12.007874, not 12.5 (which doesn't exist). If you have 12R-22.5's, they are the older bus tires that will be cheaper then the newer 315/80R-22.5. Use the 315's if you have a weight problem. Good Luck, TomC

busshawg · May 01, 2009, 11:30:26 AM

As mentioned these tires are old technologie and I would be careful about buying old tires. If he tires are new that's fine but not aways is a good looking tire a good tire, meaning if they are old you might find yourself going to all the work of getting these tires and switching them and get down th eroad far enought to get them warmed up and boom, there's the first one gone. I personally would never go back to 900 x 20 tire.

Have Fun

Dallas · May 01, 2009, 11:45:29 AM

Sorry if I upset your sensibilities Tom.
When I went to school 305 mm was 12.007874015748031" Maybe California changed it and didn't tell the rest of the world?
315 mm was 12.401574803149606"
265 mm was 10.433070866141732"
275 mm was 10.826771653543307"
285 mm was 11.220472440944881"
295 mm was 11.614173228346457"

I was speaking to Sean in generalities, not in specifics, especially not in the specifics of only using one catalog to quote from.
I'm glad you live at such a lofty altitude.

Quote from: TomC on May 01, 2009, 09:57:39 AM
I guess some are making up tire sizes. Looking in my Michelin book, I see a 275/80R-22.5 and the other manufacturers make the 295/75R-22.5-but no 285/80R-22.5-there is a 295/80R-22.5 though. In regional transit bus tires, there is a 305/70R-22.5, a 305/85R-22.5, but no 305/80R-22.5. Also, 315 converts almost exactly to 12.007874, not 12.5 (which doesn't exist). If you have 12R-22.5's, they are the older bus tires that will be cheaper then the newer 315/80R-22.5. Use the 315's if you have a weight problem. Good Luck, TomC

TomC · May 01, 2009, 12:41:37 PM

Sorry all-Dallas is correct-I was using the wrong multiplyer. Good Luck, TomC

gus · May 01, 2009, 08:14:44 PM

TomC,

I have to disagree with you, 9.00 x 20 is not a tubeless tire. Only the .5 sizes are tubeless.

Liken SLC, I had a M35A2 Deuce & 1/2 that had 10 of that size tire on it, all had tubes. I also have a '42 GMC ten wheeler with ten 7.50 x 20, all with tubes, a '52 GMC with 12.00 x 20, all tubes and a few others with 9.00, 10.00 and 11.00 x 20, all with tubes.