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BAC Forum    General Boards    Technical Support  ›  Tire sizes/weight carrying capacity Moderators: Gerald Farris

Tire sizes/weight carrying capacity  This thread currently has 4,982 views. Print
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Steve Adams
November 12, 2010, 8:29am Report to Moderator

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When we purchased our 2001 Beaver Contessa 40' the previous owner had installed Toyo 265/75R22.5 Load Range G tires. The maximum carrying capacity listed for that tire is 5205 pounds at max pressure. We had the coach weighed and the front end weighs 10400 without a driver or passenger. The data plate for the unit says the front axle is rated for 10,400, how convenient! Sitting still we are at the capacity of the tires and axle and we are not going to change the axle. We have the same issue with the left rear where the weight is 10,800. If I'm reading the chart correctly the dual capacity for this tire is 4805 X 2 = 9610, or 1200 pounds below the actual weight. The right side weight is 8,800 which is well within the range of the existing tires.

I cannot seem to find a tire that will give us the weight carrying capacity we need in the 265/75R22.5 size. The closest I have found is 275/80R22.5 or a 275/70R22.5

When I compare the tire sizes this is what I'm seeing;

Mfg                  TOYO                     Goodyear/Michelin
Size           265/75R22.5        275/70R22.5        275/80R22.5
Diameter          38.5                      38.0                  39.7          
Width               10.9                      10.9                 11.1          
RPM                 540                       545                   524            
Single              5205                     6945                 6175        
Dual                4805                     6395                 5675      

Oddly enough when I went to the Les Schwab site the 265/75R22.5 was greyed out, meaning no longer available.

Besides the obvious improvement in capacity with either of the new tires, is there enough of a difference in the other characteristics to make a difference in how they fit? Both say they will fit the rims I have which is one good thing.

While I'm at it I'll take recommendations on tire pressure monitoring systems. Brands, model #'s, etc. Internal sensors or external (valve stem sensors), any issues with sending units, the need for repeaters, etc.

Thanks in advance for your input.

Thanks, Steve


Steve & Cathy
2001 Contessa 40'
330 CAT/Allison
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Bruce Benson
November 12, 2010, 11:05am Report to Moderator
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We found that the Toyo tires wear irregularly, perhaps from the overloading.  Our steer axle now has Michelin XZA2 Energy 295/80R/22.5 LR H which gives us 7830/6940 up from the 11R22.5 LR H with 6610/6005 that came from the factory.  We do have some wheel well drag on a very tight turn.  Not sure what the difference is, if any, in the wheel well between yours and ours.

I think that Good Year has a chart on their web site that show the diameter of the different tire sizes.  I remember using it to try to keep the tires as close to original as possible.  The new ones are quite a bit wider though.

The axle rating is based on the weakest item on the assembly including the tires.  It is possible, but not absolute, that your tires were that weak item when the max load was established.  The tires are certainly the most likely item to fail if overloaded.  
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Richard And Babs Ames
November 12, 2010, 2:05pm Report to Moderator

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We have had rivering wear on the front steer tires with Goodyear G159 and G670 275/70 R 22.5 H on our coach and just changed to Michelin XZA 2 Energy 275/70 R 22.5 J tires. We have not traveled far enough to see a wear pattern yet.

Motorhome originally had 255/70 R 22.5 H tires and after two front tire failures we went to the larger tire. We were able to reposition the front axle to get proper clerance when turning. Beaver/Magnum actually had a procedure for the axle reposition to accomodate the larger tire but if you mentioned "overloaded axle" they would clam up and walk away.

We have had three front tire failures and Toyo stood behind the first two and a sidewall failure on the largers tire was a Goodyear G670 and they stood behind their tire also.


1997 Beaver Patriot
3126B  CAT  
South Central FL
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LEAH DRAPER
November 12, 2010, 3:24pm Report to Moderator
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Regarding TIRE PRESSURE MONITORS.....(While I'm at it I'll take recommendations on tire pressure monitoring systems. Brands, model #'s, etc. Internal sensors or external (valve stem sensors), any issues with sending units, the need for repeaters, etc. )


For a number of years I used Pressure Pro and was so DIS-SATISFIED I finally  checked out and purchased a new system.  The Pressure Pro would never give me accurate readings, many times it could not even sense pressure on the motorhome, let alone the toad even with a repeater which ran the battery down to dead on the toad!  It was confusing to setup, you have to remove the sensors to check pressure with a gauge, the alarm was constantly going off in-accurately, one can NOT at a glance see what the pressure ready is, and the tire temp is not available.

I now have the Tire-Safe Guard by GENCO which is absolutely great!  It constantly lets you see the pressure and temp of each tire, and warns if outside the parameter settings, can be calibrated to closely match the reading of a good digital gauge,  you don't have to remove the sensor to take a reading by a gauge particularily on the motorhome and if you have metal stems on the toad you can do the same.  
I had metal stems put on PT Cruiser sometime prior with new tires so I ordered the same sensors for all.

Check it out....../www.tiresafeguardusa.com/compare.html

Leah  http://www.tiresafeguardusa.com/compare.html Clickible link


2008 Contessa (425 hp Cat) 38'
PT Cruiser/SMI braking
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Joel Ashley
November 12, 2010, 10:24pm Report to Moderator

Go OSU Beavers Class of '73. RVing 29 years
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Just as a precaution, check the capacity stamped on the rims also, as they can fail if overloaded;  if factory original they are probably fine as long as the coach is loaded within specs.  Our coach is off side to side in the back also, by 1500lbs; yours by a ton.  I haven't quite determined exactly why there is such a significant difference, but no one, including Bend and the RVSEF seems concerned, as long as both sides' tires are inflated to allow for the heaviest side.

One main concern is tire width beyond what the dual rim spacings were designed for;  you don't want radials scrubbing each other back there.  Don't know why your chart width shows the same (10.9) for the 265 and 275, because they are by definition 10mm (~3/8") different.  If that's correct, the 275's should mount 1 cm. closer together than your 265's.  The 275/80R's have a sidewall more than 3/4" wider, which affects coach height;  conversely, the 275/70R's calculate to sit about 1/4" lower than the 265's, making them your most likely candidate, though their load rating may be higher (J?) than needed (H?).

Other BAC members are more expert on tires than I, so hopefully they will add some input for you.

-Joel


Joel and Lee Ashley
36 ft 2006 Monterey
C9 400HP Cat
Beaver Believers
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Richard And Babs Ames
November 13, 2010, 12:32am Report to Moderator

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Tire manufactures have approved rim widths for mounting in their data and it is easily accessable. The Big thing is that some wheels are rated to 120 psi cold and the tires are rated higher. Used the lowest psi cold rated componet be it tire or wheel.


1997 Beaver Patriot
3126B  CAT  
South Central FL
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Gerald Farris
November 13, 2010, 4:19am Report to Moderator

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Steve,
It does not sound like you are comparing tires with the same load rating. In the same load rating,, a 275/80 will carry more load than a 275/70. Regardless if your tires are that badly overloaded, you need to upgrade them.

First you need to determine how much room you have to go to a larger size tire. You have to be careful about the tires rubbing when turning because there is probably an air bag located directly behind the front wheel housing. If the tire rubs too much on the wheel housing when turning, the air bag will be damaged. After you determine how large of a tire you can use, you can then compare the tires that are available in that size to best suit your needs. You will probably find that the 275/70/22.5 in a load range H is the tire that will best fit your needs.

Gerald  


2000 Marquis, C12
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Gary Schenck
April 25, 2011, 1:51am Report to Moderator
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I have lots of questions.  We just purchased a 1989 Beaver Marquis with 10x22.5 tires.  The two front tires are about 18 months old by mfg date.  The two outside duals are 9 and 10 yrs old.  We will not be traveling over 200-250 miles...no real long cross country trips.  Should I consider the tire monitor system mentioned earlier on this thread to monitor the tires.  Or should I consider getting new tires?   Also, how do I find the load capacity of the rims?  Or the PSI ratings on the rims.

Thank you to each one who responds with their experience and knowledge.
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Gerald Farris
April 25, 2011, 3:03am Report to Moderator

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Gary,
First the load capacity and maximum air pressure of the tires is molded in the sidewall of all of your tires and the load capacity and maximum air pressure of the wheels is stamped in the wheel. The stamp on the wheel will be on the inside so you can find it on your rear outside dual wheels.

The load capacity will not do you a lot of good unless you know what the coach weighs. Do not believe the factory weight labels. Weigh the coach packed the way that you travel. an inflate the tires according to the actual weight of the coach using the tire manufacture's weight/inflation tables. If you do not know what the coach weighs, I would run the tires at their maximum inflation.

As for as your 9 or 10 year old tires on the rear of the coach, I would replace them now. The life expectancy of your tires is 6 years. Some people stretch that to 7 years, but no one should be driving on 10 year old tires.

As for as purchasing a tire pressure monitoring system, I use one for convenience, but a good tire pressure gauge will do the same thing with the exception of reading the pressure as you drive so that you are notified if a tire starts loosing pressure as you are driving.

Gerald


2000 Marquis, C12
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Joel Ashley
April 25, 2011, 10:19pm Report to Moderator

Go OSU Beavers Class of '73. RVing 29 years
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I have to agree with Gerald, Gary.  You need to get new rear tires asap.

Tire pressure monitors are nice to have, but I've not splurged for a set;  if you're going to do it, you might as well monitor all 10 tires - coach and toad (12 with a tag axle).  That can get spendy.  I use a laser temperature gun myself, to just check for an inordinately hot tire at the end of a travel day.  It's not as good, perhaps, as monitoring on the road, but truckers use the guns as an option/addendum to tire thumping, and it works for me.

-Joel


Joel and Lee Ashley
36 ft 2006 Monterey
C9 400HP Cat
Beaver Believers
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Gary Schenck
May 7, 2011, 6:31pm Report to Moderator
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New tires going on now
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Steve Adams
June 16, 2011, 4:34am Report to Moderator

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I took the first step today and went to Les Schwab to see what they had. What they are recommending is an 18 ply Michelin XZA2 Energy Low Profile Highway Tubeless tire in 275/70R-22..5. My current tires are Toyo's, 14 ply in 265/75R-22.5. The tires are very similar in size so I don't think that will be an issue.

What I need is more weight carrying capacity and these tires will boost me from 5200 to 6900 lbs per tire. My question is, is the 18 ply to much? Will the ride suffer by running this tire vs a 16 ply? I'm just concerned they may be too stiff.

The price is right and they are in stock. Thoughts please.

Thanks, Steve


Steve & Cathy
2001 Contessa 40'
330 CAT/Allison
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Steve Adams
June 16, 2011, 4:40am Report to Moderator

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I forgot to add, that Schwab is recommending a product called Counterbalance, to run inside the tire for dynamic balalcing.  It comes with a special valve stem that, reportedly, eliminates issues of something getting stuck in the stem that will cause the tire to leak.

My son-in-law's dad is a long haul trucker, who recommends centramatic balancers.  Essentially, they bolt on between the duals in the rear, and on the steers, and have a tube on the outside that is filled with steel shot,  I guess doing the same thing as the Counterbalance.

Anyone using either of these products? Opinions?

Thanks, Steve


Steve & Cathy
2001 Contessa 40'
330 CAT/Allison
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Joel Ashley
June 16, 2011, 8:00am Report to Moderator

Go OSU Beavers Class of '73. RVing 29 years
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Just keep in mind, Steve, that weight carrying capacity is more than just about the tires.  Never load your rig to exceed the chassis load ratings specified for your particular coach - GVWR and GAWR's.

I'll leave it to others with balancer experience to respond to your basic question, and several members are well-healed regarding your tire size inquiry  .

-Joel


Joel and Lee Ashley
36 ft 2006 Monterey
C9 400HP Cat
Beaver Believers
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Gil_Johnson
June 16, 2011, 3:51pm Report to Moderator
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You can't have too much tire.  I'd opted for the high load range tire so they wouldn't have to be run at their maximum load capacity.  As Joel stated, make sure youy never exceed the axle ratings.
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