Optimal tire PSI from factory?

[Maverickxeo]

On my 21 Sport S Unlimited, the tires were at 40PSI (I lowered to 38PSI as per the door sticker). Looking at the tires themselves (Michelins), they have a max PSI at 44PSI at 2500lbs.

From my understanding, the vehicle weights around 4500-4600 lbs (curb).

Based on the math (2500x4 = 10,000); (4600/10,000 x 100 = 46%); (46% of 44 = 20); is it correct to say that even the door panel, which says 38PSI, is far too much for the factory tires? I've used this math on my TJ (that is heavily built) and I find the ride quality and tire wear are great - not sure how the MPG is though!

I know plenty of people have lowered their tires to around 36ish PSI - is there a big drop in MPG in doing so? I honestly don't care about tire wear on these tires - I want to burn them off (they really suck in the snow...).

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[BDinTX]

Interesting math but I think maybe that it assumes sidewall and tire flex is linear or is directly proportional to tire pressure.

It is frequently recommended to do a chalk test on your Jeep, and your tires.
On mine around 32 - 34 PSI yielded the best tread contact with my combination.

 

[Maverickxeo]

Interesting math but I think maybe that it assumes sidewall and tire flex is linear or is directly proportional to tire pressure.

It is frequently recommended to do a chalk test on your Jeep, and your tires.
On mine around 32 - 34 PSI yielded the best tread contact with my combination.

That makes sense, I know the math is very rough, haha!

Are you running the same tires and "Stock" weight of the Jeep? Does it ride well, and still get decent MPG?

 

[Dyolfknip74]

Google "chalk test, tire pressure"

Math is bullshit.

FYI, I run my 35" E Load Duratracs at 30 PSI cold. No noticible change in mileage. (it's still the shits)

 

[Maverickxeo]

Google "chalk test, tire pressure"

Math is bullshit.

FYI, I run my 35" E Load Duratracs at 30 PSI cold. No noticible change in mileage. (it's still the shits)

Haha, bad milage is based on opinion - I'm happy with what my JL gets (I get much more than in my TJ - TJ gets about 15MPG, haha!)

 

[donmontalvo]

All three of my Jeeps (my two previous and my current) were new and given to me with tires inflated to 40 psi. When I asked about it, the dealers told me it’s a requirement. Strange response, seemed consistent between the FL dealer (first Jeep) and the PA dealer (second and current).

I set mine to 37 for long highway driving. No real reason other than the door jam label recommendation. I’m 1,000 miles from home (returning from EJS) maybe I’ll try the chalk test to see how far off I might be.

Hoping to avoid a “paper trail” of tires being slightly below 37, that might work against me if something happens. With that said Jeep is of course aware that when our tires are at 10-15 we’re off-road.

 

[BDinTX]

We moved up to 315/70r17, put on a lift, and added a bumper and winch at mostly the same time on both Jeeps. So slightly heavier now than in stock form.

The 2.0T is averaging mid 18 I think and the 3.0T is mid 23 for mixed driving. Highway driving at 70-75mph mileage will reduce it by 1-2mpg on both. I'm not certain what the MPG was before the add ons but I think it was about 2 MPG better on both. I suspect the lift impacted economy more than the tires but I don't know for sure because of the timing.

 

[rcadden]

Bone stock from the factory on my Sahara Altitude 2.0T, I was getting ~19-21MPG average (hwy+street) at about 37 cold.

I've since swapped to 33" KO2s with a 2" puck lift and steel bumper (no winch), and I keep them at about 35 cold. With all that, I still average 16-18 MPG, depending on how I'm driving.

 

[JL Diesel]

We moved up to 315/70r17, put on a lift, and added a bumper and winch at mostly the same time on both Jeeps. So slightly heavier now than in stock form.

The 2.0T is averaging mid 18 I think and the 3.0T is mid 23 for mixed driving. Highway driving at 70-75mph mileage will reduce it by 1-2mpg on both. I'm not certain what the MPG was before the add ons but I think it was about 2 MPG better on both. I suspect the lift impacted economy more than the tires but I don't know for sure because of the timing.

Curious. Did you get the computer flashed after your lifts? Or have a Taser? My mpg dropped more than I was expecting after putting the 35s on but without doing a flash I wonder if it’s my shift points being off.

 

[BDinTX]

Ya I went with AEV lifts and those come with a tool to change tire size, TPMS warning threshold, and a couple of other things. I'd definitely recommend getting something to adjust your tire size. Tasers seem to have a lot of features and are pretty popular.

 

[BDinTX]

Bone stock from the factory on my Sahara Altitude 2.0T, I was getting ~19-21MPG average (hwy+street) at about 37 cold.

I've since swapped to 33" KO2s with a 2" puck lift and steel bumper (no winch), and I keep them at about 35 cold. With all that, I still average 16-18 MPG, depending on how I'm driving.

I see you posting on here and in the local Facebook groups. How is it we haven't hit a local park at the same time? : )

 

[Old Dogger]

I run the Tires on our JKR and JLR, at 35 psi cold.. At this pressure, they ride nice and wear even. But I also rotate them every 5 to 6000 miles. Plus have then re-balanced at time of rotation.

 

[rcadden]

I see you posting on here and in the local Facebook groups. How is it we haven't hit a local park at the same time? : )

I mean ... I post here and on the local FB groups when I'm hitting a park, so what's your problem, man?







I kid, I kid. Heading to Hidden Falls for Memorial Day, actually. Interested?

 

[Reinen]

FYI, Jeep tires are intentionally over inflated at the factory to prevent flat spotting during storage and shipment. Dealers should air down the tires to 37psi before turning over to the buyer but few do. So that's just part of unwrapping your new Jeep. Beyond that, chalk test and fine tune.

 

[donmontalvo]

FYI, Jeep tires are intentionally over inflated at the factory to prevent flat spotting during storage and shipment. Dealers should air down the tires to 37psi before turning over to the buyer but few do. So that's just part of unwrapping your new Jeep. Beyond that, chalk test and fine tune.

Makes sense.

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