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06-10-2015, 10:59 AM
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#1
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Junior Member
Join Date: Jun 2015
Posts: 1
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Tire pressure question
Hi,
I'm the new owner of a 2004 Gulf Stream Sun Voyager (first motorhome) and it came with 2 year old Sumitomo ST727 275/70R 22.5" tires.
I got the coach weighed after we moved all our stuff in and my per-wheel weight is ~3700lb all around, which is off the bottom of the chart for those tires.
The lowest weight rating on the Sumitomo chart ( http://www.sumitomotire.com/assets/p...ck_Catalog.pdf) is 4920 (single) and 4590 (dual) at 85psi.
Does that mean I can safely run the 85psi with plenty of safety margin?
Thanks in advance for any advice.
-Matt
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06-10-2015, 05:39 PM
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#2
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Senior Member
Monaco Owners Club
Join Date: Jun 2014
Posts: 14,603
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Yes, seems like you have a lot of safety factor.
__________________
Jim J
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi
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06-10-2015, 07:25 PM
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#3
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Senior Member
Join Date: Feb 2009
Location: Colorado
Posts: 379
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I run mine @ 100 to 105 psi and never weighed the coach in 13 yrs of ownership. On my 3rd set of tires now and never have had a tire problem.
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06-10-2015, 08:32 PM
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#4
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Senior Member
Join Date: Aug 2001
Location: North America somewhere
Posts: 30,971
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Run what the tire placard inside the MH states and you can't go wrong.
The RMA= Rubber Manufacturers Association,pg 51, states to never run less air pressure than what the tire placard states.
quote: "
Inflation pressure recommendations may also be
determined based on the tire manufacturer's
specifications, which define the amount of inflation
pressure necessary to carry a given load. These
inflation pressures may differ from those found on
the vehicle tire placard or certification label.
However, never use inflation pressure lower than
specified by the vehicle tire placard, certification
label or owner’s manual. Nor should inflation
pressure exceed the maximum pressure molded on
the tire sidewall."
__________________
2000 Winnebago Ultimate Freedom USQ40JD , ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA. " My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy
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06-10-2015, 09:27 PM
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#5
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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The pressure on the sidewall of a Michelin RV tire and many others is not the "Maximum" the tire should ever have (unlike car tires) it is the minimum to support the maximum rated carrying capacity of the tire.
From the Michelin RV Tire Guide:
Quote:
"If you look at the tire's sidewall, you'll see the maximum load capacity allowed for the size tire and load rating, and the minimum cold air inflation needed to carry the maximum load."
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From page 6 of the GoodYear RV Tire and Care Guide:
Quote:
"How much air is enough?
The proper air inflation for your tires depends on how much your fully loaded RV or trailer weighs. Look at the sidewall of your RV tire and you’ll see the maximum load capacity for the tire size and load rating, as well as the minimum cold air inflation, needed to carry that maximum load."
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From TOYO:
Quote:
Q: What are the consequences of inflating the tires to accommodate the actual loads?
A: If the inflation pressure corresponds to the actual tire load according to the tire manufacturer’s load and pressure table, the tire will be running at 100% of its rated load at that pressure. This practice may not provide sufficient safety margin. Any air pressure loss below the minimum required to carry the load can result in eventual tire failure.
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But then they go ahead and publish a weight/pressure chart allowing lower pressure for RV's!!
From the August 2010 Motorhome Magazine "Tread Carefully" tire article:
Quote:
The maximum load capacity allowed for the size tire and load rating and the minimum cold air inflation needed to carry that maximum load are located on the tire’s sidewall.
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__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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06-10-2015, 09:42 PM
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#6
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Senior Member
Join Date: Nov 2003
Location: Richmond Hill, GA USA
Posts: 707
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I have the same tires on my coach, and they are very good tires.
With your weights, I would run 85 psi in the tires, and you'll have a good safety factor.
Enjoy your coach.
Fred
__________________
Fred & Vicki
St. Augustine, Fl.
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