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Old 11-09-2018, 10:20 AM
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PSI Recommendations

I'm running 35" KO2's on my JL. The tire shop set the PSI's to 50.

My MPG's took a bigger hit than expected and I'm wondering if it may be because they aren't at the right setting. Went from 17 city to 13 mpg.

I've read on unrelated threads that the recommendation for 35" is 29 PSI in cold weather. I live in Miami which rarely gets below 75 degrees.

What would you recommend I set it to?

Running 18' Fuel Vapor alloy wheels and a Magnaflow MF series Axle back exhaust. (in case anyone is wondering for MGP purposes)

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Old 11-09-2018, 10:27 AM   #2
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I've run 35, 37 and 40s, C, D and E rated, all set 26-28 PSI.

YMMV

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Old 11-09-2018, 10:35 AM   #3
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A good starting point is 30-32... Most of us run 26-28 in our 35's and 37's. But it wont help your MPG... Did you get a tuner for your tire size? If you haven't changed tire size, you're getting a bad reading.
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Old 11-09-2018, 12:42 PM   #4
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I run 28 PSI in my 34" KO2s. Seems to be the sweet spot.

You have to remember that one of these LT-E rated tires by itself weighs more than a factory wheel+tire+TPMS sensor+weights combined. Your fuel economy is always going to take a massive hit with anything over 33".
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Old 11-09-2018, 12:53 PM
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That makes sense, sounds like i'm running way too high a PSI. Will bring it down to 32 PSI to start and see how it feels.

Not too concerned about the MPG's to be honest. Wouldn't have gotten the wrangler if I cared. The stock tires were Goodyear Adventurer with Kevlars and they were 32's but the KO2's are definitely a lot thicker so did expect a drop in Gas mileage.

My main concern is ensuring they are inflated at the right level for ride quality and durability of the tires.

Given what I had on, do you recommend I get a tuner?
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Old 11-09-2018, 01:38 PM
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Just took a second look and noticed a couple of things, I'm hoping you can help me out with.

Manually measured each tire and they are set to 35 PSI. I will go back and reduce each to 32 as per the advice on this thread.

What I need help with is the Tire Pressure gauge in the dash. It is reading 50PSI's. Could this be an issue with the TPMS sensors themselves or do i need to have something reset in the dash? Can i do it myself or should I take it to the dealer?
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Old 11-10-2018, 06:03 AM   #7
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Quote:
Originally Posted by Bluesteeljl View Post
Just took a second look and noticed a couple of things, I'm hoping you can help me out with.

Manually measured each tire and they are set to 35 PSI. I will go back and reduce each to 32 as per the advice on this thread.

What I need help with is the Tire Pressure gauge in the dash. It is reading 50PSI's. Could this be an issue with the TPMS sensors themselves or do i need to have something reset in the dash? Can i do it myself or should I take it to the dealer?

Drive it after setting pressures as it takes about a mile to re calibrate to the dash.


You should also try a lower setting after you drive with 32 for a while and compare that with say 28.
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Old 11-11-2018, 09:04 AM   #8
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I've been running the 35x12.5R18 KO2's for 3 years on my 4 door JK. I have found that 29 psi cold is the best for me. Once I get to about 32 psi the ride feels too stiff. They are E rated which doesn't help the ride quality.

Pressurized makes an important point about setting your tire size with a programmer. If you haven't done that, your speedometer, miles, and mpg are all wrong. I use a Superchips Flashcal on my JK. I have no idea what's available for a JL.
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Old 11-11-2018, 06:48 PM   #9
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There is a flashcal for the JL.

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