Tires - sizes & costs

[David T. Richelderfer]

I am getting near to the years of usage that I need to be looking at getting a new set of eight tires.  And, if you have been reading recent posts in another thread, Gerald and Keith opined that I am not running enough weight-bearing capacity on at least my front-end tires.  One suggestion was to reduce my tag axle push-down pressure to take some weight off the coach's front-end.  When I purchased the coach two years ago it was set at 35 pounds push-down pressure on the tag axle.  I reduced that to about 30 pounds.  I will make plans to get on a scale and reduce that push-down pressure to 25 or 20 pounds and see what the coach's front-end weight does.

1. How do I determine if 12R 22.5/22 or 315/80R22.5 tires will fit in my front-end wheel wells without rubbing on tight turns?

2.  Who do I ask?  Are there some Beaver owners of heavy coaches like mine who already have switched to these larger tires either all-around or on the front-end?

The Michelin 295/80R22.5 XZE2+ COACH X tires on the coach are 16 ply, and at their maximum cold pressure of 120 psi still are not carrying the front-end load.  Their weight rating (at 120 psi) is under 8k pounds.  The coach's front-end weighs about 16.3k pounds full of fuel and fresh water.

I went to Les Schwab's this afternoon.  They suggested two brands at my prodding for larger tires.  Two OHTSU 12R-22.5/16 R-200 tires would cost $1,040.14 mounted and balanced.  Being a 16 ply tire I am guessing even this tire may not have a heavy enough weight rating... but I did not ask.

The other suggestion was two DOUBLE COIN 315/80R-22.5/22 tires which would cost $1,134.18 mounted and balanced.  These tires, being 22 ply, have a 130 psi maximum cold pressure rating and would carry a maximum of 20k pounds... well over my front-end weight of 16.3k pounds.

I plan to check around more before making a purchase... at Goodyear, at Commercial Tire, at Big-O, etc.

Comments and/or suggestions and/or voices of experience are welcome...  DTR

[Jeff Watt]

David,

I'll leave the major discussion to others, however I put Michelin xza2 energys 315s on the frong on my coach. Did so for a little more capacity, but more for foot print. The problem that arises is that I am running 8.25 rims which significantly downgrades weight capacity; the 315s on 9 inch rims have  quite a bit more capacity and can be inflateted to 130 but on the 8.25 rims max pressure is 120. I have the Michelin guide somewhere and will try to post it later (i'm on the road). Don't know about the tires you are looking at, although I suspect that rims play an issue regardless of brand.

Jeff

[David T. Richelderfer]

Yes, the Les Schwab guy mentioned wheel rim width as a factor, and as you pointed out, the 315 and 12R tires call for the larger wheel rim width of 9 inches.  Thanks for adding that.  I had forgotten that the Les Schwab guy mentioned it.  Soooo... what do new shiny 9 inch wide wheels cost?  lolol

[Larry Williams]

David,

At the prices you quoted, it would be worthwhile for you to check out the FMCA Michelin Advantage program. The XZA2 ENERGY 315/80R22.5 is $586.18 plus $52.83 FET plus installation. I got mine installed by Less Schwab in Junction City, OR. That does not answer your question about fitting your rig and wheel price, but that is significantly less than what you quoted for the other brands.

[David T. Richelderfer]

The prices I quoted above were for TWO tires, not one tire.  And those prices were all-in, including FET (I believe), and mounting and balancing.  Even with this correction, the name-brand value of Michelin tires may be worth the extra $100 or so per tire.  The Michelins now on the coach certainly give a nice smooth ride... like a boat on a lake on a calm day.

[Gerald Farris]

David,
You should be cautious about the load capacity of the tires you are looking at. The common load range for the 12/R/22.5 will carry the same load or less than the 295/80/22.5 tires that you are now running.

To determine if your coach can clear the 315/80/22.5 tires or what ever you decide on, go to the tire manufacturer's website and check the difference in diameter between the 295s and the new size. Then go to your coach and measure the clearance that you now have in turns as well as when the suspension is deflated. If you have 2 inches of clearance and the larger tires are one inch larger, they will fit. But if you have only one inch of clearance and the new tires are one inch or more larger, they will not fit.

Your other options are reducing tag axle pressure to reduce front axle weight, or load modification by moving heavy items in the basement closer to the rear axle and not traveling with a full water tank unless absolutely necessary.

Gerald  

[Terry Melot]

Gerald, good point about not traveling with full tanks.  I realized that 100 gallons of water weighs 833 lbs. If I'm not planning on dry camping for a week, I never need that much fresh water in the tank. I have since reduced my normal load to around 30 gallons of water or about 250 lbs. As the fresh water tank is closer to the front axel than the drive axel, that took several hundred pounds off the front. If I were traveling from one wet camp to the next, I could get by with 10 gallons or 84 lbs.

[Bob Jae]

Terry don't go to low you may need water on the road for the engine or if you get waylaid for a repair you might need some extra water.

[Keith Moffett]

Gerald
I am interested in your comment comparing the 12R to a 295.  The Michelin chart compares the 12R to the 315.  Also I measured the over all diameter and the sidewall of each size and they appear the same where the 295 is smaller.  
Is there something I overlooked?

Keith

[Larry Fisk]

I visited with a fellow BAC member at BCS this week that had the 315 tires on the front of his Marquis that damaged his coach just as Gerald said because he didn't have enough clearence. He was going to look into getting his air bags adjusted to give him more clearance and then see if they could repair the damage. I think I'm going to stick with the 295's.

[Gerald Farris]

Keith,
If you compare the load capacity of 12R to the 295/80 or 315/80, at the Michelin website (http://www.michelintruck.com/reference-materials/manuals-bulletins-and-warranties/load-and-inflation-tables/), you will see that the 12R load capacity compares to the 295/80 and not the 315/80.

Gerald