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Old 05-11-2015, 06:25 AM   #15
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4. Possible reduction in the slight amount of sway without buying a new anti-sway LDH

This makes me conclude you already have and use a LDH ( Load distribution Hitch) also called WDH ( W for weight).
then there is less load on rear wheels of truck and more on front of truck and TT tires, then it would have without LDH.
Think you then can do the European calculation , where to law you must have between 1% and 10% on towbar of GVWR. American law is minimum 10% , maximum 15%.
Mostly then about 5% and in my TT spreadsheet I use 4%.

Now I only need the tire data of truck and TT , and the axle loads.
Try to find them and I will give a picture of my filled in spreadsheets in return.
From tires already know AT-pressure for the truck, only now need maximum load and speedcode, and same data of TT tires. Also give exact sises of TT and Truck tires, for TT probably ST tires are used.

Load to use for TT also know =7000lbs.
For truck need maximum speed you use and tire or axle loads determined as acurate as possible.
Sou you dont have to get mathematical, yust give the needed data and I will do that for you.

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Old 05-11-2015, 08:16 PM   #16
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Originally Posted by rideandslide View Post
Thanks All

Did not realize i was opening suck a mathamatic question here's why i choose to put E rated LT tires on my 2013 Ram 1500 5.7

1. Need new rear tires
2. For the slight increase in cost, for a increase in load capacity ( not that i need it)
3. Want a more AT tread if needed.
4. Possible reduction in the slight amount of sway without buying a new anti-sway LDH

I was told by Discount Tire Direct to run them at 45 psi for normal street, and max when towing. I not much on using max ( except if i want the most sway control, any proplem in using max. pres. ) i'm thinking 70 psi while towing.
I repeat!

Use the weight/ inflation chart for your tire. Weigh your truck with and without a load. Add 5psi to what the chart says.

80psi will beat you to death.

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Old 05-11-2015, 09:37 PM   #17
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Did not realize i was opening suck a mathamatic question here's why i choose to put E rated LT tires on my 2013 Ram 1500 5.7
More than the majority of RV folks will ever know . But when we over tire a truck that much there are lots of pros and cons to consider.

Maybe I missed it but those OEM P metric tires max load capacity may be 2200 -2300 lbs and comes at 35 psi max. Pressures may increase but the load ratings doesn't.

Now look at a LT tire chart which says for a LT245/75-16 E at 2200-2300 lbs comes at 50-55 psi range.

I would agree 45 psi would be a good pressure for a 1500 truck with LT E tires with no load.
How much more pressure with your small load ??
Weighing the truck axles when loaded will tell the tale but I would bet 60-65 psi would be worlds of plenty.
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Old 05-12-2015, 05:12 AM   #18
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Thanks All
Will have to get to a scale and check them numbers

Miss spoke when i said installed, meant ordered, tires came in today, Pathfinder made for Discount Tire Direct by Kumho ( was told, and checked online ). Very happy with the tread pattern ,60,000 tread wear, will post results when i get them mounted, heading out for a week today, wish they had so up a little earlier.
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Old 05-12-2015, 08:34 AM   #19
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If you have Discount Tire install them have them look up the psi/load ratings for you. They did when I had my Michelin LTX 2 E's put on my F150. Get it from the horses mouth not the internet.
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Old 05-17-2015, 08:56 PM   #20
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E rated tires are much stiffer than normal truck or auto tires. My Michelin M/S are triple belted steel radials and don't change shape whether I have 45 or 80 lbs in them. I don't believe you have that much more flex at a lower inflation pressure.
I usually run 50 lb but up to 70 when I tow.
When in doubt follow Smokey's advice and you won't have problems.
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Old 05-17-2015, 09:22 PM   #21
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Originally Posted by SmokeyWren View Post
Nah, the math is not that difficult. But ignore the shade-tree mechanics and use the industry standard method to determine the proper PSI for your tires.

In the USA, we have the Tire and Rim Assn (TRA). The TRA is a bunch of engineers that determine the specs for tires and wheels sold in the USA and Canada). The TRA publishes the load/inflation tables for all sizes of tires sold in the USA. They have done most of the math for you, so you just have to do enough math to apply the load/inflation table to your tires.

But the tire companies don't like to publish the TRA load/inflation tables for the sizes they sell because they don't want the liability when someone misapplies the info. So instead of telling you to apply the load/inflation table for your size tire, they beg off by telling you to follow the vehicle manufacturer's instructions. So the TRA load/inflation tables are usually available only from TRA, and you have to be a TRA member to get them. And being a TRA member is expensive.

Toyo tires to the rescue. They publish the TRA load/inflation tables, and make them available to their customers. So click on the following link and you can see them.

Tires 101: Tire Load & Inflation Tables | Toyo Tires

So here's the drill. First you must know the load (weight) on the tire. Weigh the rig on a CAT scale to get the weight on each axle. Divide that weight by the number of tires on that axle to get the weight on each tire. Then apply the load/inflation table.

Example: Load range E tires that might be mounted on a half-ton pickup could be size LT245/75R17E. Here is the load/inflation table (from the link above) for that size tire when mounted on single wheels (not duals).

PSI . Max load
---- . ----------
35 . 1770
40 . 1945
45 . 2110
50 . 2270
55 . 2430
60 . 2595
65 . 2755
70 . 2900
75 . 3050
80 . 3195

Unless you overload your pickup, you will probably never have enough weight on you rear axle to require more than 40 PSI, so maybe pump them up to 45 PSI just for grins. But don't pump them up to anywhere near the 80 PSI they can handle, else you'll wear out the center of the tire tread and the truck will ride "rough".
Since I have joined this site I have learned more from your posts than just about anyone, thanks for the link to Toyo. I bookmarked it for future use.

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