295/80R22.5 tires

[rpasetto]

Originally Posted by richard5933

Some 315s are rated for the 8.25 rims even though the charts will show that a 9.00 is recommended. As an example, we have Firestone FS400 on our coach. They are 315s and the chart shows a 9.00 rim is recommended. On a 9.00 rim the max pressure is 130 psi.

Careful reading through the tire data book shows that the FS400 can be mounted on 8.25 rims, but then the max pressure is downgraded to 120 psi, and the max load on the tires is also downgraded to that shown for 120psi in the chart.

If you have a 315 in mind, and if it will have adequate clearance and dual spacing, it's worth a phone call to the manufacturer to see if they have a similar downgraded rating for their 315 mounted on a 9.25 rim.

Originally Posted by richard5933

Can't tell you why, but when I researched this in preparation for new tires, I found that not all manufacturers support/suggest/stand behind their 315s being mounted on the 8.25 rims.

............................................

I did some reading, specifically in the Continental and Michelin tire books. In the old Michelin tore book I downloaded when I was researching tires I had found that the 315/80R22.5 tire was downrated when used with an 8.25" wheel. Derated, the max inflation shows 120psi with a weight capacity of 16000#/axle and at 110psi, 14920#/axle. The 295/80-R22.5 Michelin Xza2enrg that I installed, at 120 psi, weight capacity was 13860#, at 115psi, 13400# and at 110psi, 12940#, so at 13000# load on the front I figured I was OK at 115psi. (Had I gone with the X-coach, at 120 psi weight cap, 15660# and at 110psi, 14600#...). So back then I did not get into what's necessary to put 315's on my Dynasty.

So now I'm looking again, may be one of the Michelins... downloaded the latest Mich data book. For every 315/80r22.5 tire found there, there's a footnote saying "Not approved for use with 8.25 wheel."(https://www.michelinb2b.com/wps/b2bc..._Data_Book.pdf)

So then I looked at Continental's book since they also have discounts for FMCA members. The HSR2-SA and HA3 tire models have the size 315/80R22.5.. but there's a restriction: "315/80R22.5 tires when used on 8.25" rims are restricted to a maximum of 7610 lb. at 120psi..." Now the HR2SA tire also comes in 295/80r22.5 (as well as 315/80) so I checked the load-inflation tables... the 295 at 115psi gives weight carry capacity of 7600# essentially the same as the 315 model at 120psi. Nothing gained and a bit lost here. I could run the Conti 295's at 100psi and be OK. So it's back to looking for 295' whether they be Mich or Conti's.
(https://blobs.continental-tires.com/...guide-data.pdf)

[Ivylog]

The 7610 lbs (max weight on a 8.25” Rim) at 120 psi is for duals. A single can support 7610 at 110 psi per your reference (page 101) on a 8.25” Rim.
The issue is the max weight that a 8.25” Rim can support...7610 lbs.

[rpasetto]

Originally Posted by Ivylog

Why would one manufacture allow 315s on a 8.25” rim and another not? If you keep reading all of the footnote on 315 on a 8.25 Rim it does not derate them when used as duals because the dual ratings do not exceed the 8.25 rim’s weight carrying capacity...the dual rating is decreased enough to not overload a 8.25 Rim.

On my 42’ 04 Dynasty there is very little clearance on the RF airbag but on my 08 Navigator with wider steps there is plenty of clearance. While I have only put 9K miles on these 315s, there is not any noticeable uneven tire wear.

Originally Posted by Ivylog

The 7610 lbs (max weight on a 8.25” Rim) at 120 psi is for duals. A single can support 7610 at 110 psi per your reference (page 101) on a 8.25” Rim.
The issue is the max weight that a 8.25” Rim can support...7610 lbs.

Here's what Michelin had in their data book back about 5 years ago:


They seem to be saying the 315's rated on the 'normal' 9" wheel, at 120psi , weight capacity runs between 8530# to 9380# per wheel for single, depending on the tire model; for duals it's showing 7250 to 7760#.
For the 8.25 wheel, they stated a max of 120psi: for singles is 8000# per wheel, for duals it's 7610#.

Somewhere between than and now their perspective has apparently changed:


Michelin now seems to be saying "not approved" for every one of their 315's on the 8.25 wheel. I do not know why the change. and cannot find anything in their literature explaining it. However I see that Conti has de-rated their 315 to levels below the corresponding 295 when used on the same 8.25" size wheel.

I hear Toyo never approved their 315's with the 8.25 wheel. will look at Bridgestone and Yokahama next...

[Michbill]

Vito,

Thank you.

WOW! What a great site.
I went there, checked exterior/Monaco and what is looking at me but 2009 Dynasty with an intact driverside fender. I sent the information to the owner of the collision shop. Hopefully, this is still an available part from them and not a "stock" photo.
Thank you.
Bill

[CountryB]

Originally Posted by rpasetto

Michelin now seems to be saying "not approved" for every one of their 315's on the 8.25 wheel. I do not know why the change. and cannot find anything in their literature explaining it.

Michelin's tech bulletin

[richard5933]

Originally Posted by CountryB

Michelin's tech bulletin

Mike - That's quite a handy tech bulletin. Thanks for digging up and posting it here.

[rpasetto]

Originally Posted by CountryB

Michelin's tech bulletin

So Michelin is saying they now disapprove of installing their 315's on 8.25 wheels for MH's ... but it is OK with them to continue on a MH which already has them.

"Michelin has repealed its approval to use 8.25x22.5 wheels on 315/80R22.5 dimension tires for new vehicle production effective January 1, 2018.

Michelin’s position is that these Motor Coach and Motor Home (commonly referred to as RVs) vehicles produced before the end of 2017 with 8.25x22.5 wheels may continue to be fitted with current 315/80R22.5 LRL products until the vehicles are retired from active service."

Well, That explains it all right.

[richard5933]

Originally Posted by rpasetto

So Michelin is saying they now disapprove of installing their 315's on 8.25 wheels for MH's ... but it is OK with them to continue on a MH which already has them.

"Michelin has repealed its approval to use 8.25x22.5 wheels on 315/80R22.5 dimension tires for new vehicle production effective January 1, 2018.

Michelin’s position is that these Motor Coach and Motor Home (commonly referred to as RVs) vehicles produced before the end of 2017 with 8.25x22.5 wheels may continue to be fitted with current 315/80R22.5 LRL products until the vehicles are retired from active service."

Well, That explains it all right.

My guess is that this has something to do with the weight load ratings, liability issues, or perhaps both.

[Jaceutah]

Originally Posted by CountryB

Unless your set on Michelin tires, take a look at the Toyo M144. About half the price and have same load rating. I have not run these tires but read about a lot of happy user of that tire on this forum.

Another happy user of Toyo M144 tires. Have had them on for 3 years now (that's EIGHT tires!) and they have been great for over 30K miles so far.

Les Schwab charges approx $500 per tire.

[rpasetto]

Originally Posted by richard5933

My guess is that this has something to do with the weight load ratings, liability issues, or perhaps both.

Sounds like Michelin has come to the realization that they did not de-rate 315's on 8.25 wheels as much as they should have. (Note Continental de-rated their 315s on 8.25's to below the capacity of a 295.)

However Michelin makes a strange statement that if the coach already has 'em, you can keep 'em.... seems they are not wanting customers rushing to them to make a gratis swap.

[kerryvan]

I just got a surprise, and wanted to share, had a front steer blowout a couple yrs ago, finally got all 8 tires switched to toyo m144, had the latest 2 new toyo put on the steers and the old steers put on the tag, the old tag were the last of the old set of tires. When the mechanic was mounting the tire on the drivers side, he noticed the studs were pulled out. After a week of searching we found 10 new studs, at 52.60 each, and will get them replaced in the morning. Bottom line the mechanic said when having a blowout it is common practice to replace the studs. News to me, but having about half of them pulled out some I could easily see the issues, and replacing them is technically easy, but expensive because Monaco used a unique stud... please spread the word to others with blowouts to check the studs....

[kketterling]

Just to add to the up sizing of tire to 315 conversation. In 2013 I installed 315s all around on my coach on 8.25 rims without any clearance issues. I now have almost 42,000 miles on the Michelins and tire wear has been even. Next year will be replacing due to age with same tire size.

[hypoxia]

I have Toyo M144 295's. My theory is to change them and sell the old tires at the 4 year point. They have more value used at that time and tires get brittle. Putting new tires on every 4 years will give a better ride. There is going to be some expense there but that is part of the joy of ownership!

[mydogmax]

I think if your tires are 6 years old they should be replaced no matte what. I have toyo tires and they are fine. 295 not 315, they are wider.