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Old 04-05-2014, 07:12 PM   #1
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confused: what pressure to run

Truck is a 2013 Ram 3500 DRW 4WD. All stock rims n tires. The sticker on the door gives me the psi of 80 for the fronts and 65 rear for max load. Sidewall of ALL tires say 80 psi for max load. Which do I follow. Also what pressure are similar trucks using when not towing for a better ride?
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Old 04-05-2014, 09:44 PM   #2
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I would use 80 all around, especially if towing. They have it as listed because of the weight bias toward the front. You should never be able to hurt a tire by running it at the listed max sidewall psi. You could experiment lowering at 5psi intervals if you are interested in a better ride when not towing. When you get to the point on the front end that is too low, you will begin to see wear on the outer edges, altho 4wd will probably wear the outside edges anyway.
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Old 04-05-2014, 10:13 PM   #3
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I would go with the door sticker pressure rating to start with when loaded and hooked up to the trailer. You can always lower the air pressure when not hauling/towing for a smoother ride.

You didn't give us a size but the Ram Body service web shows a LT235/80-17 E at 3080 lbs capacity for a single application (front axle) and 2835 lbs for a dual application (rear axle).

I find it best to weigh the trucks front and rear axles separately when loaded and hooked to the trailer. And weigh it again with the trailer unhooked. This will give some numbers for proper tire pressures and you know your trucks exact loaded/unloaded axle weights

Your tire maker will have a tire pressure/load chart. The front tires have a single tire pressure application and the rears come under the dual pressure application for the weight they carry.
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Old 04-06-2014, 07:35 AM   #4
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Quote:
Originally Posted by sdnative1970 View Post
Truck is a 2013 Ram 3500 DRW 4WD. All stock rims n tires. The sticker on the door gives me the psi of 80 for the fronts and 65 rear for max load. Sidewall of ALL tires say 80 psi for max load. Which do I follow. Also what pressure are similar trucks using when not towing for a better ride?
Truck tire ratings are MAX that they are rated for. They can be run at 80PSI and be safe.
The truck ratings are recommended for the truck's max load.

One way to find out how much air you need is using chalk. It also depends on your load.
Run the truck around and get the tires up to operating temp. Then go to a flat concrete or asphalt surface, and mark a chalk line across the treads. Drive forward a few tire rotations until you see the chalk line wear.
Chalk line fading the middle is too much air pressure for your load.
Fading on the sides is too little air pressure for that load.
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Old 04-06-2014, 07:56 AM   #5
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Hi sdnative1970 I have a Ram DRW 4WD and I have found that when towing a 18000 lb 5th wheel I ran 65psi in front and 65 to 70 psi in the duals. But if you run that psi in the rear empty you will wear the center on the tires from to much air. When empty I run 65psi in front the Cummins is heavy, and 35psi in the rear duals but if you haul you need to air up for the load. It works for me.
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Old 04-06-2014, 08:11 AM   #6
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23,000 miles at 80PSI and my tires are all even across the tread. It may ride a bit harsh when empty, but the tradeoff is worth it to me not having to try to access the inner dual valve stem all the time.
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Old 04-06-2014, 08:17 AM   #7
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Quote:
Originally Posted by wingnut60 View Post
I would use 80 all around, especially if towing. They have it as listed because of the weight bias toward the front. You should never be able to hurt a tire by running it at the listed max sidewall psi. You could experiment lowering at 5psi intervals if you are interested in a better ride when not towing. When you get to the point on the front end that is too low, you will begin to see wear on the outer edges, altho 4wd will probably wear the outside edges anyway.
Joe
X2 The pressure is on the sidewall.
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Old 04-06-2014, 01:07 PM   #8
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Originally Posted by JIMNLIN View Post
Your tire maker will have a tire pressure/load chart.
Some do, most don't now. They tell you to go by the vehicle manufacturer's recommendation, which gives only max PSI without overloading the vehicle.

All tires sold in the USA must comply with the load/inflation tables developed and published by the Tire and Rim Assn. Every tire size has a different load/inflation table. And the tire size in those tables apply to all tire manufacturer's, so Goodyear, Michelin and Toyo and other brands will all have identical load/inflation tables for a tire size if they choose to publish them. One tire manufacturer that still publishes those tables is Toyo.
Load & Inflation Tables | Toyo Tires
So you can use the Toyo tables reqardless of your brand of tire.

Here is the load/inflation table for size LT235/80R17:

Max weight in lbs. for PSI
PSI .. dual .. single
--- .. ----- ... --------

35 .. 1570 ... 1725
40 .. 1725 ... 1895
45 .. 1870 ... 2055
50 .. 2040 ... 2270
55 .. 2155 ... 2370
60 .. 2290 ... 2515
65 .. 2470 ... 2680
70 .. 2555 ... 2805
75 .. 2675 ... 2940
80 .. 2835 ... 3085

Note that the only one of those numbers on the tire sidewall is 3085 @ 80 PSI. But when you drive an unloaded dually with only 6,000 or less pounds on the rear axle, you can safely air down the rear dually tires to 35 PSI with no damage to the tires.

If you read the fine print about load/inflation, you will note that they recommend increasing the PSI by 5 or 10 PSI for high speeds (over about 65 MPH). So if you drive in west Texas where the speed limit in 80 MPH, you'd want to run a minimum of 45 PSI in your unloaded dually's rear tires.
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Old 04-13-2014, 05:48 PM   #9
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I run mine at the door jamb pressures. It is specified for the maximum load of the truck and I don't exceed the maximum load... I can't see any reason for running over the MOPAR recommended pressures if I'm not overloading and the ride is much better. In fact, my truck will take 45 psi in the rear when empty and after I unhook, if I'm going out sightseeing, I air down to 45 psi for the better ride and air back up before hooking up to leave.
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Old 04-14-2014, 09:06 AM   #10
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Old 04-14-2014, 01:56 PM   #11
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This is advice given to class A owners.

Scale the beast, fully loaded.. In your case It is a bit simpler than with an A because if your 5th wheel receiver is properly installed the weight on the right and left side of the truck will be within a few pounds of the same... (never exact but close enough to ignore)

So pull across a segmented scale so your front wheels are on one segment, our rear on another and your trailer on a 3rd.

Now you have axle weights.. you can make the following calculations.

Front plus drive axle = Total Truck GVR, Is it more or less than the truck's rated GVR

Axle weight /number of tires on axle = tire load.. Someone has provided the inflation chart already for your tires.

Truck weight plus trailer weight = CGVW Is it more or less than your trucks max CGVWR.. if so you are overweight get a Trail-Hauler (just put www. and .com around it and you will get the meaning)

NOTE: I am not accusing you of being overweight, Just like pointing folks to Trail-haulers,,, for the RVer who does not want to ask "Can my truck tow that?"
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Old 04-14-2014, 10:30 PM   #12
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SmokeyWren is correct, I have used his tire pressure suggestions since 2011 on my Chevy dually...go with the door sticker if you want your truck to ride like a lumber wagon. The tire load inflation pressure chart should be on the door IMHO.
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Old 04-15-2014, 10:20 AM   #13
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Originally Posted by webslave View Post
I run mine at the door jamb pressures. It is specified for the maximum load of the truck and I don't exceed the maximum load... I can't see any reason for running over the MOPAR recommended pressures if I'm not overloading and the ride is much better. In fact, my truck will take 45 psi in the rear when empty and after I unhook, if I'm going out sightseeing, I air down to 45 psi for the better ride and air back up before hooking up to leave.
Exactly. His tires have a load rating at a given psi. The psi and the trucks load rating are matched up and that's the number on the door.

I.E, my 12 Ram calls for 75f-80r for max loading. Reason is that those psi numbers are matched to the trucks GAWR. My front is 4900, rear is 6000. Tires have a 3000lb rating at 80psi. 75psi gives the tire a 2450lb rating.
Same goes for the OP. 65psi in the rear x4 gives him the RAWR he needs.

That's why there's two different psi ratings on the door sticker. One for empty, one for loaded. It's all based on the tires load rating at a given psi.
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Old 04-16-2014, 08:48 PM   #14
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Originally Posted by sdnative1970 View Post
Truck is a 2013 Ram 3500 DRW 4WD. All stock rims n tires. The sticker on the door gives me the psi of 80 for the fronts and 65 rear for max load. Sidewall of ALL tires say 80 psi for max load. Which do I follow. Also what pressure are similar trucks using when not towing for a better ride?
That's what the door sticker on my Chevy Duramax dually calls for too. I've used those numbers since 2002 and been happy. We used to tow a 15,500 lb, 5er. I think the total mileage was about 81,xxx miles towing.
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