315/80R22.5 In Place Of 12R22.5 Tire?

[stillcous@yahoo.com]

I am new to the forum, so hopefully I have stated everything you need to know to help me with my questions.

I cut a tire when turning into a campground yesterday on the rear outside dual-my bad-should have had the wife outside watching me. While backing into the campsite, the tire was flat and is now loose on the rim. I have a 40’ 2003 Beaver Marquis with a tag axle. I have Toyo 12R22.5 tires on all three axles with 2011 date codes and the style of the tires is M111z. The local Toyo dealer can’t find the M111z style, not sure if Toyo even makes this style any longer. I will purchase two new tires and take one of the tires I replace to use for the outside rear tire that I ruined since they have the same mileage and wear.

The local dealer does have two M144 in a 315/80R22.5 that I could put on the front axle or tag axle. I looked on vin plate and the tires shown were the 12R22.5 with 8.25” rim width. Looking on Toyo’s specification for the 315/80R22.5 tires shows a recommended rim width of 9 to 9.75”. What problems do you think I may encounter if I purchase the 315/80R22.5 tires and install them on the 8.25” wide rims-or would the 315/80R22.5 tires even fit on the 8.25” rims? If the 315/80R22.5 tires fit on the 8.25” rims, would I be better to install the 315/80R22.5 tires on the front axle or tag axle?

If I can’t get the 12R22.5 tires, do you think I could remove both tag tires, and use one to replace the cut tire on the dual and then drive home? I am about 1000 miles from home. The vin plate shows 47,000 lbs. and I had just weighed my coach a couple of days ago. It weighed 40,700 lbs with a full tank of fuel, ½ full (50 gallons) on the fresh water, ¼ full (12 gallons) on the gray tank and ½ full (25 gallons) on the black tank. I do pull a trailer with my coach and it weighs 9,900 lbs.with 960 lbs. tongue weight.

Thanks for any advice.

Doug

[kaypsmith]

If the tag tires are the same as the duals, I have in the past moved a tag tire up, then have a reasonable tire mounted for the tag. This way, the duals all remain the same, the tags if slightly mismatched should not be an issue.

Also, call on truck stops in the area that handle tires,12X22.5 is a common truck tire, although most are using 11X22.5 these days. I have used 305 85 in a pinch, it should be pretty close in height, and will fit 8.25 rim.

You might look up Tireman9, and send him a PM, he is the real tire expert on the forum.

[dickandlois]

Doug, Welcome to the FMCA Forum !

Have you looked at this thread on the Forum ?

http://community.fmca.com/topic/8327-matching-hard-to-find-tires/

Covers some of the issues when trying to match tires and a little information on how best to match and mix tires depending on there location.

Like Key said, Tireman is our tire go to man and he will add his knowledge to the mix.

Rich.

[tireman9]

Saw the question this AM and wrote a reply, then had errands to run. I must have shut down computer before hitting the SEND.

Give me about an hour and I will re-post the info.

[tireman9]

OK Quick re-cap.

The 315/80R22.5 M144 specs rim width of 9.0 - 9.5 so I would not use that tire on an 8.25 rim.

Toyo has a 12R22.5 in a M170 design that does fit your rim.

You only gave the total unit weight so we can't do any calculations to confirm capacity or Load Range needs. This information would be good to have.

Now for mixing tires:

Front axle. Both tires should be same size / Brand / Design / & inflation

Drive All 4 tires should be be same size / Brand / Design / & inflation PLUS each pair of tires in dual need to measure within 3/4" OC of each other when fully inflated but not loaded so probably moving the current tag tires to one side of duals will work or maybe better. Move the two fronts to the drive dual position and put two new tires on your front axle.

Tag Since this is free rolling it really just needs to be same size tires and same inflation

Be sure to record the full size, design and DOT serial for each tire while doing all the switching around.

Let us know when you calculate the corner weights for each axle of the RV so we can confirm your proper Cold Inflation Pressure "CIP"

[stillcous@yahoo.com]

Thanks everyone for your replies and much needed help. I tried for several days to locate Michelin 12R22.5 tires but the local dealers did not have any and said the Michelin tires were on backorder. So I call the Advantage hotline and Ed said there were two 12R22.5 tires in Michigan. When I asked the larger local dealer to check out what it would cost to ship the tires from Michigan to Nashville, they were reluctant to get me a price. I called several days in a row and could never get a price, so I gave up on the local Michelin dealer.

The local Toyo dealer couldn't get any tires shipped in to Nashville within the week. The only tires I could find in the Nashville area were the Dunlop 12R22.5 150L SP348 RSS H (16 Ply), so I purchased two and had them installed on the front axle. The front axle tires were the same brand and model as the tire that I cut on the back axle (Toyo M111z 12R22.5). The tire serviceman didn't think much of measuring the circumference of the inside dual tire and the replacement from the front. He said since the tires were the same size and model, you should only measure the thread depth. There was only 1/32" difference in the thread depth between the inside dual and the replacement tire from the front axle, so he went ahead and installed it.

I now have one Toyo spare tire in case I may need it. The downside is the Dunlop tires are rated for 9” wide rims, so I’ll have to find out what the de-rating of the Dunlop tires would be for the 8.25” rims. I plan to get my corners weighed as soon as I can so I know how soon I should replace the Dunlop tires. All the rear tires have manufacture dates in 2011, so if I don’t have to replace the Dunlop tires immediately, I plan to move the Dunlop tires to the tag axle and purchase new tires for the front and rear axle, in a year or two.

Again, thanks for the advice.

[mpierce]

I own a trucking company, and drive myself. 12's are NOT a common truck tire. Since my Bluebird uses them, I checked at a number of truck stops, and truck tire companies last fall driving around the US. NOT ONE of them carried 12's!

305 is a close replacement.