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Old 10-05-2013, 11:42 AM   #1
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School me on E rated tire pressures

Hey guys, Im a little confused about this, so if anyone has a clue, by all means, tell me what Im missing.

Im looking to get 315/75/16 Duratracs for the new rig. I have seen many people talk about running them at 25psi, 28psi, 30, etc. Discount Tire told me that their minimum psi rating is 35psi. Now, Im not sure if they are telling me that for liability reasons or that is really the minimum they can be run at. I figured since they are E rated, they are extremely over-rated for the Jeep and can be run a lower psi.

Can anyone make me understand any of this?

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Old 10-05-2013, 01:32 PM   #2
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I bet they are telling you that because of the rating on the door and the tpms. When I switched the sensors from 2011 to 2013 when I bought the new jeep, DT would not put in less than 35psi even when I asked then to only inflate to 30 psi. The guy told me he had to go by what was on the door. So I just aired them down right in their parking lot before I drove off.

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Old 10-05-2013, 01:42 PM   #3
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According to you, What is or who has told you what "E" rated tires mean.. For me "E" is the load rating.. which means.. more plys more durrable and can be inflated (max 50 plus psi)
Now one thing to keep in mind.. many tire companies simply scan your door pannel for the factory settings.. and adjust to those settign with your new tires.. Mind you and this seems odd they (tire center) didn't take the time to look at the tire thats actually on your jeep.. and these tires are or require you to adjust the psi to soemthing other than whats on your door jam.. If you follow me.

So in my eyes.. Disregaurd the door jam sticker when installing tires that arent factory fresh.. Several times I've had places like Jiff or Valvo scan my door jam and attempt to adjust the psi on my tires.. and thats one of two things I don't let anyone touch..
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Old 10-05-2013, 01:53 PM   #4
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all i can tell you is what i run in my 35/12.5/17 nittos.which is 26 psi on the highway. 8 to 10 offroad. ive was told to run a piece of chalk across the tread take a short drive and lower the psi till the chalk line goes away all the way across the tread.oh ya im in a 2 door jk. a 4 door may need a lil more psi
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Old 10-05-2013, 03:00 PM   #5
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Because the Jeep is relatively light compared to pickups who run the same tires, they require less air to ride and wear properly. Tire pressure is determined by vehicle weight alone, for example a. 7,000 pound truck would require 50psi in the tires to produce the same sidewall bulge as a JKU at 27psi.

For reference, I run 27psi in 35x12.50x17 Pitbull Rockers on a JKU, chalk test proved this to be the best pressure. Tires are rotated every 5000klm, tread depth checked across tread at every rotation, now at 50,000klm the wear is clean and even.
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Old 10-05-2013, 03:22 PM   #6
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I run E rated 285 70 17. The ride was terrible like a pogo stick. After lowering to 30 psi the ride is much better than originally, but I still feel the axle jumping over ripples in the pavement. I may go lower psi, but already the tires are bulging slightly at the bottom.

So, yeah.
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Old 10-05-2013, 03:29 PM   #7
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I run my MTRs (E rated) at 25psi on the road. Air down to 10psi normally on the trails. On really ugly stuff I have gone down to 6psi. I would not try this with a C or D rated.

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Old 10-05-2013, 04:31 PM   #8
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I have cooper MTs 35x12.50x17, in town I run them @ 26psi. On the trail I run 15psi. I got tired of shops seeing the TPMS light on and adjusting the pressure so I got the FlashCAL from superchips and eliminated the TPMS.
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Old 10-05-2013, 04:35 PM   #9
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On road 24 psi, Chalk for optimal pressure.
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Old 10-05-2013, 05:51 PM   #10
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Sounds good boys. I'll start off at 30 and go from there.
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Old 10-06-2013, 07:02 AM   #11
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I wish GY would make the DT in a 35x12.50/15. They would ride so much better than the metric E tire.
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Old 10-06-2013, 07:45 AM   #12
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My 295/70/17 Nitto's Trail Grappler MT's (E rated) arrived from DTD inflated to 80PSI.

They're now down at 33 PSI and I could go a bit lower I think (30PSI?). Haven't done the chalk test yet.
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Old 10-06-2013, 07:51 AM   #13
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My 37x13.50x17 Toyo Open MT E-rated seem to like 33psi for comfortability on the street, I go a little higher on long trips, and down to 10-14 psi off road.
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Old 10-06-2013, 08:20 AM   #14
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I'm on 33 psi with my 315/75/16 duratracs, have not done a chalk test but I did lower it from the 37 psi the shop had put in and it rides better.
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Old 10-06-2013, 09:32 AM   #15
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The Difference in Ratings

The load range or ply rating branded on a tire's sidewall helps identify how much load the tire is designed to carry at its industry specified pressure. Passenger tires feature named load ranges while light truck tires use load ranges that ascend in alphabetical order (letters further along in the alphabet identify stronger tires that can withstand higher inflation pressures and carry heavier loads). Before load ranges were adopted, ply ratings and/or the actual number of carcass plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.

Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.

I run KM2's that are E rated. I run them at 32 PSI for DD and off road I will take them down around 18 PSI. I have had no problems. I ran a chalk test at 32 and that was perfect for me.
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Old 10-07-2013, 07:19 PM   #16
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The Discount Tire here just will ask where you want the PSI, I had them set it at 29 psi last time. It's probably a store policy or something, it's not all Discount Tires.

Mine have really flexed on the PSI with the weather changes. In the cool mornings they drop as low at 26, mid-day warm temps bring them up to 29, sometimes 30 psi again. We get a "hot" day in the high 80's and they will hit 30-31 again. This is by what the EVIC is showing, but it's pretty close to accurate.
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Old 02-27-2014, 06:10 PM   #17
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Ok I am looking at buying new tires and looking at e rated tires what is the r e and ware like with E rated tires. From the sounds of it the biggest down side is weight but this is my wife's daily driver and my toy so have to keep her happy too.
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Old 02-27-2014, 06:17 PM   #18
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Have a look at the manufacturer's load inflation table for your tire size sometime. One thing you will notice is that the amount of air specified for a given load and a given tire size stays constant regardless of the load range. In other words, take a C rated 255/75R17 and an E rated 255/75R17. Both tires require the same air pressure to support the same load. The difference with a higher load range tire is that you can run more air pressure.

So there's the theory. Basically, in theory, your tire pressure should be exactly the same as it would be with the same size tire in any other load range.

In practice, I'd do a chalk test. But I do think there is value in understanding the background on how this works.
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Old 02-27-2014, 07:13 PM   #19
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My E rated Dyratracs are great on the road at 28-30 psi. Much higher will rattle your brain on bumpy roads.
The chalk test along with trial and error.
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Old 02-27-2014, 09:41 PM   #20
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Quote:
Originally Posted by i82much View Post
Have a look at the manufacturer's load inflation table for your tire size sometime. One thing you will notice is that the amount of air specified for a given load and a given tire size stays constant regardless of the load range. In other words, take a C rated 255/75R17 and an E rated 255/75R17. Both tires require the same air pressure to support the same load. The difference with a higher load range tire is that you can run more air pressure.

So there's the theory. Basically, in theory, your tire pressure should be exactly the same as it would be with the same size tire in any other load range.

In practice, I'd do a chalk test. But I do think there is value in understanding the background on how this works.
That theory works if the load on the tires is heavier. Using a high load rated tire on the same vehicle requires a lower PSI.

In the end, as you said, you really need to do the chalk test.
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Old 02-27-2014, 09:45 PM   #21
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I run mine at 28 cold which is around 30 hot. Rides and feels great!

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