Home » Public Forums » GMCnet » Re: [GMCnet] Weight On Each Wheel - How To Measure?
| Re: [GMCnet] Weight On Each Wheel - How To Measure? [message #147703] |
Mon, 24 October 2011 17:23  |
rallymaster
Messages: 662
Registered: February 2004
Location: North Plains, ORYGUN
Karma: -4
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Senior Member |
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Clip from Michelin tire data pdf. at:
http://www.michelinrvtires.com/assets/pdf/RVTiresBrochure.pdf
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Let’ s consider an RV running on 275/80R22.5
MICHELIN®
XZA3®+ EVERTREAD LRG tires, with actual
corner weights of 5,400 lbs. on the left front tire,
5,175 lbs. on the right front tire, 8,500 lbs. on the left
rear duals, and 9,200 lbs. on the right rear duals. For
control of the RV, it is critical that the tire pressures be
the same across an axle. Therefore, we must “overinflate”
the right front tire and the left rear duals. Checking the
load/inflation table below shows that a cold tire pressure
of 95 psi will support 5,510 lbs. on a single front tire.
To determine the pressure for the rear duals, again
take the heaviest position, in this instance the right rear
weighs 9,200 lbs. The load/inflation table below shows
that a cold pressure of 85 psi will support 9,380 lbs. on
2 dual tires. It is important to note that the cold inflation
pressure for the tire must never exceed the maximum
inflation rating that is stamped on the wheel.
REMEMBER: For control of the RV, it is critical that the
tire pressures are the same on both sides of an axle.
On Mon, 24 Oct 2011 16:46:49 -0500 A. <markbb1@netzero.com> writes:
>
>
> Robert Mueller wrote on Mon, 24 October 2011 15:31
> > G'day A.,
> >
> > I'm confused or maybe I'm just misreading the question below.
> >
> > I have never heard of the requirement that you have to adjust tire
> pressures by the weight on each wheel separately.
> >
> > I checked the Maintenance Manual and there's nothing about doing
> so in there.
> >
> > Regards,
> > Rob M.
> Rob,
>
> I don't know if it is in the maintenance manual, but to get the
> correct amount of area of tread in contact with the pavement, for
> traction, braking and wear, and to keep the sidewalls at the proper
> profile, to prevent the plies from wearing out and also to correctly
> absorb road impacts, each tire would need to be inflated based on
> the weight on it.
> With the design of the rear end, both tires on a side are probably
> real close to the same, but the load can be a lot different from one
> side to the other and also front to back, and for both fronts. If
> the load is more than 250 pounds different on one side of the front
> than the other, it is out of spec and some cargo needs to be
> rearranged. In my case, I need someone or something in the
> passenger seat because I weight 275 pounds, putting the front end
> out of spec just by being in it.
> I wouldn't just weigh the motorhome and divide the weight by 6 and
> inflate each tire the same. That would make some over-inflated and
> some underinflated, shortening the life expectancy of the tires,
> potentially increasing braking distance, and maybe costing MPG. Not
> to mention ride quality and handling.
> --
> '73 23' CanyonLands
> _______________________________________________
> GMCnet mailing list
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>
Ron & Linda Clark
1978 Eleganza II
North Plains, ORYGUN
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Ron & Linda Clark
North Plains, ORYGUN
78 Eleganza II
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| Re: [GMCnet] Weight On Each Wheel - How To Measure? [message #147706 is a reply to message #147703] |
Mon, 24 October 2011 17:42  |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| rallymaster wrote on Mon, 24 October 2011 17:23 |
Clip from Michelin tire data pdf. at:
http://www.michelinrvtires.com/assets/pdf/RVTiresBrochure.pdf
---------
Let’ s consider an RV running on 275/80R22.5 MICHELIN® XZA3®+ EVERTREAD LRG tires, with actual corner weights of 5,400 lbs. on the left front tire, 5,175 lbs. on the right front tire, 8,500 lbs. on the left rear duals, and 9,200 lbs. on the right rear duals. For control of the RV, it is critical that the tire pressures be the same across an axle. Therefore, we must “overinflate” the right front tire and the left rear duals. Checking the load/inflation table below shows that a cold tire pressure of 95 psi will support 5,510 lbs. on a single front tire.
To determine the pressure for the rear duals, again take the heaviest position, in this instance the right rear weighs 9,200 lbs. The load/inflation table below shows that a cold pressure of 85 psi will support 9,380 lbs. on 2 dual tires. It is important to note that the cold inflation pressure for the tire must never exceed the maximum inflation rating that is stamped on the wheel.
REMEMBER: For control of the RV, it is critical that the
tire pressures are the same on both sides of an axle.
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I guess this "argument" has morphed into the importance of balancing the load (at least side to side, not necessarily front to back) in order to maximize tire life, traction and handling.
Although I am not sure that the RV in the article is comparable to the GMC which has tandem wheels and not duallies, and automatic ride height control.
Still the article illustrates that inflation pressure of a tire on an axle needs to be set according to the weight on the axle. And in my mind the GMC has six axles.
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| Re: [GMCnet] Weight On Each Wheel - How To Measure? [message #147733 is a reply to message #147706] |
Mon, 24 October 2011 20:58 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Senior Member |
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| ahamilto wrote on Mon, 24 October 2011 15:42 |
...
Still the article illustrates that inflation pressure of a tire on an axle needs to be set according to the weight on the axle. And in my mind the GMC has six axles.
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Do not let the toll booth people know that... they think we have 3 axles.
While our rear wheels do share the load like dual wheels, they are not side by side so they do not have the load issues. So use the "single" chart.
With our suspensions I would go with front wheels get the same pressure based on the highest loaded front tire. All four rear tires get the same pressure based on the highest loaded rear tire.
Years ago I weighed and looked up the pressures. for my 26 foot I have been using 60lbs in the front tires, 55lbs in the rear ones. My Birch (lighter, 23 foot) gets about 5lbs less per tire.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Weight On Each Wheel - How To Measure? [message #147737 is a reply to message #147733] |
Mon, 24 October 2011 21:49 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| Mike Miller wrote on Mon, 24 October 2011 20:58 |
| ahamilto wrote on Mon, 24 October 2011 15:42 |
...
Still the article illustrates that inflation pressure of a tire on an axle needs to be set according to the weight on the axle. And in my mind the GMC has six axles.
|
Do not let the toll booth people know that... they think we have 3 axles.
While our rear wheels do share the load like dual wheels, they are not side by side so they do not have the load issues. So use the "single" chart.
With our suspensions I would go with front wheels get the same pressure based on the highest loaded front tire. All four rear tires get the same pressure based on the highest loaded rear tire.
Years ago I weighed and looked up the pressures. for my 26 foot I have been using 60lbs in the front tires, 55lbs in the rear ones. My Birch (lighter, 23 foot) gets about 5lbs less per tire.
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I try to avoid toll roads and bridges.
From what I have read, it is best to balance the load side to side the best you can. Based on balancing the load side to side, and the way the suspension balances the rear load on a side to both wheels, inflating all the rears to the same pressure would work. But I would still like to know what the rear loading is by side so I can better balance the load. Same for the front.
To get it someplace that I can weigh it, I planned to start with 55 - 60 pounds in all six and then add or release air once I know the loading.
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| Re: [GMCnet] Weight On Each Wheel - How To Measure? [message #147751 is a reply to message #147737] |
Tue, 25 October 2011 03:22 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I usually tel people to start with 60 on the rear and 65 on the frontsand monitor hte tire temperatures after drigin for 50 or 100 miles at highway speeds. If all tieres are similar temps then youa re in the safe zone. Thes values give a few PSI extra in case they have the torsion bars or rear ride height out of adjustment causeing unbalanced weights on the various axles.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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