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Discussion Starter #1
They say 80 psi on the sidewalls, I suppose b/c they are 10 ply or something like that. What should I be running them at? The dealer took them down to 35 and told me they were at 60 (Discount Tire mounted them) What I am looking for is the best psi for gas milage/anti-wear, etc. Any suggestions?
 

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They say 80 psi on the sidewalls, I suppose b/c they are 10 ply or something like that. What should I be running them at? The dealer took them down to 35 and told me they were at 60 (Discount Tire mounted them) What I am looking for is the best psi for gas milage/anti-wear, etc. Any suggestions?
Due to the size your running i'd recommend keeping them at 35 psi. The 80 psi on the side wall is the max psi for that tire. I have the same size as you and im running 35 psi and have even tread wear. If you want you could alway run it a little higher but I wouldnt go over 38 psi. Thats just my .02
 

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Discussion Starter #3
Due to the size your running i'd recommend keeping them at 35 psi. The 80 psi on the side wall is the max psi for that tire. I have the same size as you and im running 35 psi and have even tread wear. If you want you could alway run it a little higher but I wouldnt go over 38 psi. Thats just my .02
So it's ok to run less than half the max?:ugh2:
 

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Different size tires require different PSI to keep proper inflation. As 07 said, 80PSI is MAX and it is so high because of the ply rating. I have found that 40 - 45PSI is a good pressure to run that size tire. However 35 would not be too low because a tire with a wider surface area would not require as much pressure to provide the same amount of support.
 

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So it's ok to run less than half the max?:ugh2:
I dont see it being an issue.

On the trail guys air down to the single digits without any problems. Obviously beadlocks are recommended when your running them that low. Without beadlock I have ran my tires at 15 psi while offroading.
 

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Discussion Starter #6
Thanks guys. I will give 45 a try. It is still lower than what Discount sent me off with albeit just a hair higher than what the dealer did.
Appreciate you guys.
 

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Exact tire pressure to run is a combination of tire construction, rim width chosen and vehicle weight. You have to figure out what is the right pressure for your tire/vehicle/rim combo.

Put about 1/2" of flour on the road the width of a tire. Drive through it. Look at the pattern made in the flour. If the tread digs in deeper in the middle, then your tire pressure is too high. If the tread digs in deeper on the outsides, then your tire pressure is too low. Play with your pressure until the depth in the flour made by the lugs is the same across the entire tire. My guess on your vehicle you'll be at around 30+ psi when you get it right.

It doesn't hurt to do this test front and rear and set pressures accordingly...different front and rear. After all, the front of your vehicle weighs more than the rear and may require slighly high pressure to get proper tread wear.

Too high of pressure and you'll burn your tires up faster and have a rough ride. Too low of pressure and you'll get worse gas mileage and generate excess heat in the tire (what lead to the Ford and Firestone Wilderness AT lawsuits and tire failures).

For the offroad comments, I run my tires at 8-10psi when offroad (38x15.50-16 tires on 16x12 wheels). Haven't lost a bead yet.
 

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Discussion Starter #10 (Edited)
5253 with the wisdom again!

If you remember nothing else, remember this
Good info from everyone. Thanks guys. Going by that chart, I may try their formula. That would be 48psi in the front and 46 in the rear.

OR---I could just put them all at 45 like I said earlier, lol.
 

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Too high of pressure and you'll burn your tires up faster and have a rough ride. Too low of pressure and you'll get worse gas mileage and generate excess heat in the tire (what lead to the Ford and Firestone Wilderness AT lawsuits and tire failures).
Also if the tire pressure is to high the center of your tread will wear out faster and if the pressure is to low the outsides of your tire will wear faster. Like stated earlier, you have to mess around with the pressure in the tires before you can get it perfect. There are so many things that play a factor.
 

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The pressure on the sidewall is not necessarily too high. If you are really loading your vehicle down and approaching the load limit of your tires, then the max inflation is exactly where you want to be.

What is the manufacturer's recommended tire pressure for a stock vehcile? I find it hard to believe on a light little unibody Jeep that's not designed for hauling heavy loads or heavy towing, that 45 psi would be the recommendation. That sounds like an awful lot of pressure. Sounds like you'll be burning up the center of your tires over time.
 

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The pressure on the sidewall is not necessarily too high. If you are really loading your vehicle down and approaching the load limit of your tires, then the max inflation is exactly where you want to be.

What is the manufacturer's recommended tire pressure for a stock vehcile? I find it hard to believe on a light little unibody Jeep that's not designed for hauling heavy loads or heavy towing, that 45 psi would be the recommendation. That sounds like an awful lot of pressure. Sounds like you'll be burning up the center of your tires over time.
The manufacturer's recommended tire pressure is 35 psi front/rear.
 

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A 6,000 pound 3/4 ton fullsize truck is heavy and runs around 40-45psi. I consider the XK light. 45psi is too much for such a light vehicle.

What does an XK weigh? 4,000-4,500 pounds?
gross vehicle weight rating (GVWR) = the maximum allowable total weight of a road vehicle or trailer that is loaded, including the weight of the vehicle itself plus fuel, passengers, cargo, and trailer tongue weight.

base curb weight (BCW) = the weight of the vehicle including standard equipment, oil, lubricants and a full tank of fuel. Does not include optional contents or other optional equipment, the weight of driver, passengers or cargo.

All weights in below table are in pounds (lbs).

Commander Sport 4X2
GVWR = 6200
BCW = 4649

Commander Sport 4X4
GVWR = 6400
BCW = 4826

Commander Limited 4X2
GVWR = 6300
BCW = 4936

Commander Limited 4X4
GVWR = 6500
BCW = 5119

Commander Overland 4X2
GVWR = 6300
BCW = 5055

Commander Overland 4X4
GVWR = 6500
BCW = 5239
 

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Discussion Starter #16
The manufacturer's recommended tire pressure is 35 psi front/rear.
Yeah, but that is with stock Forterras that are not nearly as big, nor do they have as many ply's. Also, the max pressure on them isn't nearly as high. This is what has me confused.
 

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The pressure on the sidewall is not necessarily too high. If you are really loading your vehicle down and approaching the load limit of your tires, then the max inflation is exactly where you want to be.

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I would never suggest to someone that he should run 80 PSI, even on a loaded Commander, even if the max pressure on the sidewall of the tires is 80 PSI. There's really no reason to run at max inflation pressure even if the vehicle is loaded up, especially considering that the Commander is relatively light weight vehicle, not a heavy-duty work truck weighing 8,000+ pounds.
 

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Yeah, but that is with stock Forterras that are not nearly as big, nor do they have as many ply's. Also, the max pressure on them isn't nearly as high. This is what has me confused.
I was just responding to the question above my post as to what the manufacturer recommends for psi, which is located on the driver's side door jam.


Also just because a tire is larger doesnt necessarily mean it takes more air. Like stated above I have 265/70R17 MT/R's with Kevlar which I can guarantee has more ply's then your Hankooks and I run mine at 35 psi and have even wear. I physically called goodyear when I got the tires and gave them all the specs of my XK and they researched the curb weight and what ever else they had to do and I was told their calculations came to 35 psi. So thats what I have been running with amazing results. No uneven wear due to incorrect tire pressure.
 

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my bfg's say 50psi, I run them at 45 front, 40 rear....depending on the load.
I used to run my autocross tires above the sidewall pressure, to get maximum performance. Don't be scuurred.

Use white shoe polish striped across the tread area to see how it is wearing.
 

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Everyone is going to have their own opinions on what tire pressure to run. Air up the tires to what you are comfortable with and go from there. If they start wearing more on the outer edges you dont have enough air in them. If it starts wearing more in the middle you have to much air in them.
 
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