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Discussion Starter · #1 ·
i just got a deal on 4 new mtr's off a rubicon, guys wife said they were too loud. these are brand spanking new still have the pubes in the middle and the red and green stripe, i paid $400. anyway they are load e which kind of sucks but o well i had them mounted today and the guy put in 50psi, seems high but they ask for 80, has any body run these and if so what psi do you run on the street. thanks
 

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Discussion Starter · #3 ·
yea i hope i dont regret the load E but it was such a deal, so basically back down to stock psi
 

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Your probably bouncing all over the road at 50psi, but you are going to get better gas mileage and the tires will last longer. You should be fine running them at the manufacturer suggested air pressure. The more air you put in the more firm your ride will be. The higher load rating will not increase the harshness beyond what you may feel from adding additional unsprung weight. Higher load ratings tend to weigh a bit more.

I keep my tires about 5-10psi over the placard. If I am going to carry any weight like mulch, top soil, stone, etc. I bump the pressure up. If you are going to add weight like bumpers, a winch or protection, you will also want to increase the pressure.

What ever you do, don't waste you time with chalk. There is no point to wasting your time with that.
 

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proper psi varies from vehicle to vehicle and tire because each one weighs differently and affects the surface contact patch of the tire so one can tell you what psi is right for YOUR truck. what you want is even contact across the surface of the tread with the street. whatever psi achieves that is right for you. the best way to determine your proper pressure is to do a chalk test or water test. do a search for details, but basically you cover your tread in either chalk or water, then roll across a flat surface to see if you are leaving even tread marks. if you are not you adjust your tire pressure and keep testing until you do.
 

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I used to run a similar size, I put them at 50 on the hwy for mileage and about 28-30 around town.. .

A good way to get a starting point is to take the max load and divide it by the max psi, then muliply by the weight at each corner... so a 245/75/16 MTR E is 3042 @ 80, so 38 lbs/psi... 04 V6 4x4 Xcab 5spd weighs 3515, and lets guess 60/40 split.. thats 1054 lbs per front tire and 703 per rear tire... so 1054/38 is 27psi front and 703/38 is 18.5 rear. Obviously thats a starting point, the rear will probably end up higher, thou will most likly be lower than the front unless you have a bunch of weight in the bed. A 50/50 weight distro gives you 23psi front and rear. Its a pretty good way to find the start. Then individual rigs will vary based on gear, and width of the rim.
 

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50 psi with rubber push in valve stems is not good. Rubber valve stems are only rated to handle 45 psi. If you look at 3/4-1 ton trucks they have metal bolt in valves to handle more pressure. They can literally blow out of the rim at high pressure. I'm sure they will ride fine and wear well at 30-32 psi. Have your alignment checked to avoid cupping the outside treadblocks and rotate frequently. They do require frequent rotations to help them wear smooth. Enjoy them-you got a great deal!
 

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50 psi with rubber push in valve stems is not good. Rubber valve stems are only rated to handle 45 psi. If you look at 3/4-1 ton trucks they have metal bolt in valves to handle more pressure. They can literally blow out of the rim at high pressure. I'm sure they will ride fine and wear well at 30-32 psi. Have your alignment checked to avoid cupping the outside treadblocks and rotate frequently. They do require frequent rotations to help them wear smooth. Enjoy them-you got a great deal!
All the 3/4 ton rigs (6) my family owns(d) have rubber valve stems from the factory... sorry didn't sell me on that...
 

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I have LT 265/75/16 E load at 26 psi. So far rides nice.
 

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i just got a deal on 4 new mtr's off a rubicon, guys wife said they were too loud. these are brand spanking new still have the pubes in the middle and the red and green stripe, i paid $400. anyway they are load e which kind of sucks but o well i had them mounted today and the guy put in 50psi, seems high but they ask for 80, has any body run these and if so what psi do you run on the street. thanks
I used to run the same tires, same size. On my truck, I needed to run them at about 26 psi front and 24 rear to get the tread to lay flat.

On road trips when the truck was packed with gear, I'd run them 2-3 psi higher than that.
 

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All the 3/4 ton rigs (6) my family owns(d) have rubber valve stems from the factory... sorry didn't sell me on that...
He missed it by 20 PSI. The standard rubber pull through stems are rated at 65psi. If you are running E load range tires that have a max pressure of 80psi, the standard rubber stems won't cut it, you have to get high pressure stems. The rubber stems that you see from the factory are high pressure stems. They usually have a different diameter. Our guys in the shop have put the wrong stems in and we had guys come back saying that their stems shot out like a gun.
 

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He missed it by 20 PSI. The standard rubber pull through stems are rated at 65psi. If you are running E load range tires that have a max pressure of 80psi, the standard rubber stems won't cut it, you have to get high pressure stems. The rubber stems that you see from the factory are high pressure stems. They usually have a different diameter. Our guys in the shop have put the wrong stems in and we had guys come back saying that their stems shot out like a gun.
Makes sense, I knew there was a rubber stem capable of 80psi.
 
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