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Old 08-12-2013, 04:00 PM   #1
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Tire pressure

Tires say 5675@125psi single 5510@125psi dual. Our weight is 3750 front per tire 3375 rear per tire is there a formula?
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Old 08-12-2013, 04:08 PM   #2
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No, there are charts published by the tire manufacturers that you follow. You need the tire manufacturers info on model, size and weight rating of your tires, then go to the manufacturers site and find the charts, then follow the pressure given. Some people add 5#'s to have a safety margin.
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Old 08-12-2013, 04:09 PM   #3
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Not mine Double Coin
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Old 08-12-2013, 04:12 PM   #4
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That's what Les Schwab put on when I got it 16 ply 245/70R 19.5
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Old 08-12-2013, 04:24 PM   #5
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Quote:
Originally Posted by patngin View Post
Not mine Double Coin
Without anything to go by then you probably should run the pressure on the sidewall. Double Coin does have a website but doesn't seem to have any charts since they're truck tires they probably figure everyone will run the max pressure.
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Old 08-12-2013, 04:30 PM   #6
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When I tried 120 it drives bad have them at 90 now
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Old 08-12-2013, 06:21 PM   #7
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Not mine Double Coin
Here's your chart. Your size is on it. Google is your friend.

http://www.doublecointires.com/files...ationchart.pdf

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Old 08-13-2013, 03:09 AM   #8
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Yes there is a formula and the lists of the tire makers are made with that.
But in Europe and America a different one is used still for C-load and up.
For P-tires( normal car tires) and XL/reinforced/Extraload American TRA swiched over to the saver European power in the universal formula as late as 2006 ,European ETRTO used this for radial tires since about 1970.
I got hold of this formula end of 2007 and made a mission of it.
Learned myself Excell to make spreadsheets for it.

Latest is my MotorhomeRVtirepressurecalculator ( tripple word value) .
But to fill this in I need to know from motorhome next.
GAWR's front and rear ( Gross axle weigth rating, what the axles may maximaly bare by law), GVWR ( gross vehicle weight rating) also handy but not crucial.
Then the configuration ( number of axles and tires on the road back ).
Then together with your ( i asume) weighed loads of 3750/3375 the spreadsheet gives also used percentage of GAWR weight division etc.

Sorry if I used some strange words or spelling , I live in Holland ( Europe)
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Old 08-13-2013, 12:19 PM   #9
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Wow thanks that is a great chart.. So it looks like 90 front 80 rear. Again thanks so much
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Old 08-13-2013, 01:59 PM   #10
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The tire sises you gave and H-load 16ply single4805 dual 4540 dont mach with the maximum loads you gave in your opening post of 5675/5510 lbs.
Even if you include the 125/120 psi difference it is not making up the difference.

So wich is it??
From your F/R 90/80 you read I make front single and rear dual.
Going from the maximum load of the chard of doublecoin, and dualload rear my spreadsheet gives 102 psi front and 97 psi rear.
Then a reserve to the weighed loads of 10%
F/R 92/88 psi with no reserve so I wont advice that.

So give the good tire specifications and I will recalculate.
In my spreadsheet I use my own formula wich gives higher pressure for the same load as the American calculation wich I checked the doublecoin chart to be made with, and even higer pressure then the saver European calculation, and to my opinion comes closest to the ever to be constructed ideal formula, wich takes care that the deflection of the tires stays the same as when maximum load and that 120 psi on the tire.
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Old 08-13-2013, 02:22 PM   #11
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They show the exact thing I put after that they have 141/140J
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Old 08-13-2013, 02:35 PM   #12
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I don't know if this came through I assume they are load range J

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Old 08-13-2013, 07:30 PM   #13
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Correct
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Old 08-14-2013, 03:32 AM   #14
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Already answered your personal mail .
Main thing was that J behind the loadindexes stands for speedcode J = maximum speed of tire 100km/65m/h. They sayd loadrange J but 16PR on sidewall stands for H load.
Also the small difference between single and dual is strange, rule is maximum load dual = 92.5% of Single maximum load. If you remove the rear loadindex from the spreadsheet ( red arrow front but then rear) , it is calculated from front with this 92.5%. Then the advice behind will be higher because of the lower maximum load dual.
Fact also is that the list of Doublecoin gives lower maximum load for the sise.
This can be explained that that list is for higher speedcode of for instance M= max speed of tire 130km/80m/h.
Filled in the spreadsheet of mine, with your optimistic given tire data. and here a picture.
Mind the maximum speed then of 65m/h and higher pressure would give more reserve for the speed. Calculated back the axle loads given by typing "=4*3375 "
then then it is calculated in the spreadsheet.
These loads look a bit like you used the GAWR. Is that true or are they weighed loads? If so replace the loads to part 1 GAWR's and leave given load empty.


You can also download by RIGHTCLICKING the spreadsheet of my examples map
https://skydrive.live.com/?cid=a526e...E092E6DC%21836
Then you can chanche it all.

conclusion at the moment, Doublecoin did some creative calculating , to give the tire a better place in the market, and probably did some things wrong in that.
Have to look back in their list what loadindex they use there.
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