thoughts on PSI (yes i searched first)

[starrskream]

SO in my KL I had stock size BFG Ko2's and loved them. I ran them at 40 psi never had a single issue. They lasted me nearly 50,000 miles. I got decent mileage20 in town and 24-26 highway. I know i will never see that in the gladiator.

Now in my 23 Rubicon i have the factory tire, (33's?) and the sidewall says max 50 psi cold. I've been running for about 500 miles on that PSI and getting terrible mileage(i know, its a jeep thing). then a thought struck me, my tires looked saggy so i did a chalk test. sure enough, no grip in the middle.

so i bumped them up to 40, then 42. did a few trips to work and back at each psi. tires only went up to 42 and 44 respectively. My in town MPG actually went up. I was averaging 10-12 at 38psi and now i was seeing 14MPG at 40psi. nothing about my daily drive changed, same route and everything.

So i came on here, did some searching and saw a post with people saying 35, and one guy said "37 is absurd." I called falken and asked them their opinions. The service rep said that 37-38 is fine, these tires can handle 40 easily cold. So long as you get even contact and adjust pressures when towing i'd be just fine.


I've been running at 40 for a couple days now and MPG seems better in the 14-15 range it rides smoother and handles bumps fine. Honestly, it feels like it is riding better than when i picked it up.


I'm curious what you guys think of this based on your experience with the factory falken tires that come on the rubicon. I've got a long trip coming up and I'd love to hear your thoughts.

thanks for the info!

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[Scott L]

Your mileage will increase once your vehicle gets broke in. That being said higher pressure usually lowers rolling resistance. Ride is subjective so if you like the way it rides keep it there. Personally I keep mine right at 30 because I like the way it rides there. But I don’t worry about mileage.

 

[Escape.idiocracy]

Chalk/contact patch check is usually the way to go…. Over inflate and you will wear the center of the tire faster than the rest. Under inflate and you build heat and all kinds of weird wear starts to show up.

https://tiresize.com/pressure-calculator/ might be fun to play with

 

[DailyMoparGuy]

I run 36 psi cold for road trips. 32 for around town (softer ride, short trips typically)

If I commuted or drove on the highway often, I’d probably stick to 36

 

[PuddleJumper]

SO in my KL I had stock size BFG Ko2's and loved them. I ran them at 40 psi never had a single issue. They lasted me nearly 50,000 miles. I got decent mileage20 in town and 24-26 highway. I know i will never see that in the gladiator.

Now in my 23 Rubicon i have the factory tire, (33's?) and the sidewall says max 50 psi cold. I've been running for about 500 miles on that PSI and getting terrible mileage(i know, its a jeep thing). then a thought struck me, my tires looked saggy so i did a chalk test. sure enough, no grip in the middle.

so i bumped them up to 40, then 42. did a few trips to work and back at each psi. tires only went up to 42 and 44 respectively. My in town MPG actually went up. I was averaging 10-12 at 38psi and now i was seeing 14MPG at 40psi. nothing about my daily drive changed, same route and everything.

So i came on here, did some searching and saw a post with people saying 35, and one guy said "37 is absurd." I called falken and asked them their opinions. The service rep said that 37-38 is fine, these tires can handle 40 easily cold. So long as you get even contact and adjust pressures when towing i'd be just fine.


I've been running at 40 for a couple days now and MPG seems better in the 14-15 range it rides smoother and handles bumps fine. Honestly, it feels like it is riding better than when i picked it up.


I'm curious what you guys think of this based on your experience with the factory falken tires that come on the rubicon. I've got a long trip coming up and I'd love to hear your thoughts.

thanks for the info!

i run 37 psi on my stock falkens, i get 19.7 avg. My 37s at 25 psi and its about 13.6 mpg.

 

[Escape.idiocracy]

i run 37 psi on my stock falkens, i get 19.7 avg. My 37s at 25 psi and its about 13.6 mpg.

? you took a 6mpg hit bumping to 37’s ?

 

[PuddleJumper]

? you took a 6mpg hit bumping to 37’s ?

i drive tenderly. I get like 9-10 if i wheel hard all weekend.

 

[Volt0]

For roads, door sticker should be what you use. My JTM says 37psi cold, go higher and it feels punchy on bumps and wanders on the highway. The chalk test, for me, came up with 36 in the front. Even treadwear should give you the most miles out of your tires.

unladen, you might try 37 in the fronts, and 1 or 2 psi less in the back. We have a car that suggests that, b/c the majority of the weight is up front. I think the JTs come out with 55% on the front ( I could be wrong ), so you’ll want to be running pretty much the same psi on all 4 corners, unless you’re carrying a load.

no need to overthink it, be mindful that as the weather improves into summer, the volume of air in those tires will expand some. You may not notice the difference as much in lower volume setups.

And, many threads on this, you’ll have worse mpgs in winter months, for multiple reasons. Cold air is thicker, fuel is blended different.

Edit: this would be slightly different for folks not running on the wildpeak 33s.

 

[starrskream]

i run 37 psi on my stock falkens, i get 19.7 avg. My 37s at 25 psi and its about 13.6 mpg.

I just did 100 miles highway, 40 cold, got up to 43 at speed. 20-21mpg

why does it seem like everyone is running a psi that makes the tires look so saggy when parked? These don’t heat up that much at speed that I’ve noted. 3-4 psi more on highway. Still safe not crowning. That’s why I started this thread. Maybe I’m missing something idk lol

 

[Maximus Gladius]

Do we all calibrate the tire size in when changing tire sizes? If not, are we posting what we see or doing the math and posting that?

I too run the KO2’s (34”) and have calibrated and with running winter gas and carrying around 200 to 400 lbs of extra weight, the dash reads 14.5L/100 which is 16.2mpg in the city.

36psi is my magic number that keeps the truck tracking straight. Ball joints are correctly torqued and I keep the air filter and mass air flow sensor clean.

I’m also at 89k kms on these tires. They’ve done well.

 

[PuddleJumper]

I just did 100 miles highway, 40 cold, got up to 43 at speed. 20-21mpg

why does it seem like everyone is running a psi that makes the tires look so saggy when parked? These don’t heat up that much at speed that I’ve noted. 3-4 psi more on highway. Still safe not crowning. That’s why I started this thread. Maybe I’m missing something idk lol

contact patch and soft ride. If i were to inflate my 37s past 27psi i would wear the center out and be only running half of my contact patch. less grip. a little bit of bulge is good. means the tire is fully contacting. besides as it spins up to highway speed that bulge will come out due to rotational force. so overinflating just decreases the contact patch your on the faster you spin it.

 

[PuddleJumper]

Do we all calibrate the tire size in when changing tire sizes? If not, are we posting what we see or doing the math and posting that?

I too run the KO2’s (34”) and have calibrated and with running winter gas and carrying around 200 to 400 lbs of extra weight, the dash reads 14.5L/100 which is 16.2mpg in the city.

36psi is my magic number that keeps the truck tracking straight. Ball joints are correctly torqued and I keep the air filter and mass air flow sensor clean.

I’m also at 89k kms on these tires. They’ve done well.

even after i calibrate i still do the math and make sure its accurate.

 

[DarthAWM]

Do we all calibrate the tire size in when changing tire sizes? If not, are we posting what we see or doing the math and posting that?

I too run the KO2’s (34”) and have calibrated and with running winter gas and carrying around 200 to 400 lbs of extra weight, the dash reads 14.5L/100 which is 16.2mpg in the city.

36psi is my magic number that keeps the truck tracking straight. Ball joints are correctly torqued and I keep the air filter and mass air flow sensor clean.

I’m also at 89k kms on these tires. They’ve done well.

Most recalibrate, its easily done with Jscan, Tazer, alfaOBD, or the AEV tuner. Jscan is the cheapest option, the hardware and license are less than the Tazer

 

[SD Rider]

Tazer here. From stock 33s to 37s and adjusted accordingly, I only dropped to 12.5mpg from 13.5mpg. Mostly in town driving, but took a day trip last month and was 12.5 to 13mpg on the freeway.

I bought it for the SPG. Smiles per Gallon! So far, no disappointments!

Oh...and I run 35psi on the road. 12-15psi offroad.

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