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Old 12-27-2012, 12:59 PM   #1
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Classic motorhome tire size questions

This was sent to me from an Airstream noob that we'll just call "Jim". He is very excited about getting his 300LE rolling down the highway. Since I have an Argosy with 16.5" tires, I figured someone here could answer his question better than myself.
I am getting confused with tires and have called everyone including Airstream who was of no help - they could not tell me what size to purchase and said "look and see what is on there now". Here is what I've learned so far but I could use your assistance. I've read everything that I can find on Airforums and that hasn't helped.

The current owner said it has on it "8R 19.5 Radial Tire tubeless Unisteel tires" I am not sure of the brand but I think they were either Goodyear or Michelin. When calling around, I am finding that this tire is not very common and will be discontinued shortly. One dealer had a 8r 19.5 Bridgestone that was $280/ea. but was only 12 ply. All the other tire people and Camping World I called said they had 225.70R - 19.5 but that tire is a bit taller and wider, so the spacing I am learning between the tires on the back dual wheels could be a concern. The Camping World tire is wider. Is there anyway you can shed some light on this issue. I then called the Michelin headquarters in SC and learned that they do still make a few of the 8R 19.5. That tire is 14 ply and the cheap Bridgestone's are 12 ply, but the same number. What I did read on web was that going from the 8r 19.5 to the 225 70R 19.5 the tires is both taller and wider. I understand that the height also effects the speedometer, that isn't as big an issue for me as the worry about the tires getting hot because they are closer together. The tires whether Bridgestone, Goodyear (from Camping World) or Michelin that are the 225 70R 19.5 all are in the $480/tire range - ouch! With the mounting, taxes, and charges for disposal of old tires we're looking at $3,307 for the 6 tires versus the Bridgestone at $1,340 for 6 tires.

So - How many ply do I need? What are others doing if the 8R 19.5 are going away, and is there an issue with the space between the rear tires - how much should I have - no specifications I can find anywhere?

What are the tire sizes on the 280-345 motorhomes? Any recent experience with purchase and cost? "Jim" will be very appreciative!
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Old 12-27-2012, 01:31 PM   #2
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Here are the tire specs for Goodyear 647's that I run in 8x19.5.

Goodyear Commercial Truck Tires - G647 RSS Details

They are M&S rated and you can see the 8x19.5 is taller than the 225-70x19.5. The rim width is also different. Many run the wider tires on the narrow rims but it is not recommended. The critical thing with the ply rating is the weight rating of the tire and the weight of the coach. There are also inflation tables as a higher weight rated tire can safely carry a lower weight at a lower inflation pressure. There is a great deal of info in this pdf.

I recommend buying a quality, name brand tire. Some of the cheap Chinese tires don't handle or ride very well.
Cheers, Dan

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Old 12-27-2012, 11:05 PM   #3
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The 8R19.5's are still around and obtainable. I bought some Gladiator tires which I know are Chinese, but have had no issues with them so far. If I were full timing or were to drive the moho more than I actually do, I would consider buying the Goodyears or other name brand. However, the Gladiators seem to be well made in my opinion.
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Old 12-28-2012, 07:22 AM   #4
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3 years ago replaced all 8 with Goodyear G670rv. I will get the size next time when at thw MH. Cost was about $2,700. The ride is much better then the Mischelins replaced.
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Old 12-28-2012, 08:25 AM   #5
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I replaced 4 Michelins with Kumho after one of the rears developed a bubble and blew. Very little tire wear, I believe the age of 10 yrs did it in. It did blow at the sidewall while waiting for a traffic light, so more plys is well worth it.
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Old 12-28-2012, 09:01 AM   #6
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Originally Posted by ViewRVs View Post
So - How many ply do I need? What are others doing if the 8R 19.5 are going away, and is there an issue with the space between the rear tires - how much should I have - no specifications I can find anywhere?

you need as many plies as it takes to create a tire with a Load Rating sufficient to carry the vehicle.

what does the manufacturer’s plate say that your axles are rated for?

note that the same tire on a single wheel axle (front, or steer, or tag) will have a different weight rating than for a dual wheel axle (rear, or drive) at any given tire inflation pressure.

you have to do the math, along with the manufacturer’s tire specification page to see if your potential tire selection “fits” the wheel you’re using. (it will tell you the correct wheel size.)

if you google “Bridgestone tire inflation chart” (pick your own favorite brand) you’ll directly or indirectly get to results like this one -

then, if the tire physically fits, does it financially fit?

in a similar situation, we recently swapped out six 9.50R16.5 tires with a complete new set of 16x6 wheels and LT225/75R16 tires. expensive, but worth it, considering the eventual unavailability of 16.5 tires. they do ride pretty nicely….

others more experienced with the 19.5s might be able to advise you better as to your alternative wheel & tire sizes.

I would only otherwise suggest that you deal with a “truck” tire dealer rather than one oriented to “automobile” tires.

Joseph & Gabrielle

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Old 12-28-2012, 09:27 AM   #7
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We had six Goodyear 8R19.5 G647 RSS "F" tires installed before we left Seattle a few months ago. the price for tires, dis-mount, balance and mount was close to $3000.00, but I would not run any other tire. Something to consider, that I did not know until we had a fresh coach next to us the other day, is Goodyear makes a tire with a different tread pattern that is NOT rated for mud and snow, as ours are. Might be cheaper if you don't plan to be in the gumbo!
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Old 12-29-2012, 01:07 PM   #8
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Thanks for all of the responses!

I found a few other threads on tires in other sections.

moho wheels and tires

Tell us what size and brand tires you have

Goodyear Tire Sale

Classic Motorhome Tires
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