Rubicon Wheel Tire Pressure

Oletimer

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I put larger 285/75R17 Cooper ATP's on my JLUS (original tires were 245/75r17). They are E rated, and I read that anything below 45psi could be detrimental to the sidewall? Discount Tire filled them to about 43-45 when I picked it up. So I've been running 45 since.

Does anyone have any experience with this? Do you always follow the pressure stated in the doorsill regardless of tire size. In my case, the original Michelin 32" tires need 36psi... so would these new Cooper 33" tires also be okay with 36psi even though they're E rated? Maybe the chalk test is best method to insure your tires are inflated properly for the load.

I mainly drive on the highway, and noticed that it's drifting to the right more since I got these tires... just wondering if it's a tire pressure issue.
It could be a radial pull, some tires just do this. Nothing much can be done about it . You may try running 5 psi more air in side its pulling to.
I run 28 psi in 35s, rides good wears good. Tracks straight.





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mlebofsky

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Rubicon with Nitto Ridge Grapplers 37x13.5 chalk tested to 28lbs
 

JIMBOX

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I've been running 30/32 PSI in my "E" RATED M&S HANKOOK/BFG tires for the last 19 years---

NO PROBLEMO !

W.E.

JIMBO
 

Halstem1

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Not sure if this is the right place... i'll keep looking at other threads but have a question on 37" tires on stock rubi wheels. I'm running 37" BFG KO2 on stock wheels. I've been trying to find the right pressure. I know what the manufacturer says for stock tires and I've tried the chalk test. My hand held gauges are all showing 28 psi. My computer gauges are all showing 32 psi. I'm still not getting a full treat pattern on the ground. Chalk test I still have about an inch or more on each side not touching. I have to get down to 24 psi or less on a hand gauge to get a full treat pattern but then steering starts to suck and it feels to squishy. Any thoughts? Stay where I'm at and not worry about the tread pattern? I feel its at least partially because of the 12.5" tire on a 7.5" rim. but a lot of you guys are running the same.

Thanks!
 

Oletimer

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Not sure if this is the right place... i'll keep looking at other threads but have a question on 37" tires on stock rubi wheels. I'm running 37" BFG KO2 on stock wheels. I've been trying to find the right pressure. I know what the manufacturer says for stock tires and I've tried the chalk test. My hand held gauges are all showing 28 psi. My computer gauges are all showing 32 psi. I'm still not getting a full treat pattern on the ground. Chalk test I still have about an inch or more on each side not touching. I have to get down to 24 psi or less on a hand gauge to get a full treat pattern but then steering starts to suck and it feels to squishy. Any thoughts? Stay where I'm at and not worry about the tread pattern? I feel its at least partially because of the 12.5" tire on a 7.5" rim. but a lot of you guys are running the same.

Thanks!
I've been playing around with 22 psi for last couple weeks. The lower i go the better it drives. I'm on 11.50 35s on stock wheel. Fuel mileage has dropped a tiny bit from 28 psi,
 

Uhdinator

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Keep in mind if you read the door label is says the PSI and the Max Cargo capacity (mine says 700lbs cargo weight 4 passgeners) So..........what I'm getting at is the recommended PSI is likely for MAX cargo capacity. If you're driving by yourself most of the time with little to no cargo........reducing to say 32 psi cold, you will likely be about 34 when highway driving and have a better ride. Also keep in mind the recommended PSI is a compromise of tire wear and MPG. I would rather air down a little and have the ride and more even tire wear, and let the MPG suffer slightly than the other way around.

If you have stock 7.5" wide wheels with 35's or 37's your tire will have more of a crown than an 8.5-10" rim and require lower psi to get a flat contact patch and will also feel more squishy than if you had a wider wheel.

On my Sport 2 dr the TPMS warning comes on @ 32. I run my 305's @ 28-30 cold so they are at 32 when warmed up.
I ignore the warning as its only a light and no annoying chimes or beeps.
 

DerekPB

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I was looking for a thread for KO2 33s on stock rims for offroad

On road I get it, chalk test...35#...37#s ish

I've run dirt/rock trails, stone creek bed ish type and have gone to 18# (again Ko2 33s stock rims) that has worked ok and not slipped a bead... But what low pressure on specific off road terrain have others run with/without issue?
 

Halstem1

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I've done similar trails. I'm on 37's and stock rims and aired down to 20 psi (according to my hand gauge) however the dash was reading 24 PSI. Not sure which was right. I'm guessing I could have aired down more, closer to 15-18 from what I've read. It was my first time out and I was too nervous to break a bead by myself.
 

DerekPB

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Thanks for the feed back. I'm planning to go to 37s later this year on the stock rims as well and was wondering about how low may be posb. without having to have the experience of popping a bead personally :CWL:
 

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Not sure if this is the right place... i'll keep looking at other threads but have a question on 37" tires on stock rubi wheels. I'm running 37" BFG KO2 on stock wheels. I've been trying to find the right pressure. I know what the manufacturer says for stock tires and I've tried the chalk test. My hand held gauges are all showing 28 psi. My computer gauges are all showing 32 psi. I'm still not getting a full treat pattern on the ground. Chalk test I still have about an inch or more on each side not touching. I have to get down to 24 psi or less on a hand gauge to get a full treat pattern but then steering starts to suck and it feels to squishy. Any thoughts? Stay where I'm at and not worry about the tread pattern? I feel its at least partially because of the 12.5" tire on a 7.5" rim. but a lot of you guys are running the same.

Thanks!
I've noticed this as well on 37x12.5 Cooper STT Pros with the stock Rubicon 7.5 wheels. I'm afraid we will have early tire wear on these wheels...Oh well, and no warranty, no biggy. Are there more serious consequences of running the stock rims on 37x12.5s I should be aware of?
 
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Halstem1

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I'm running 37" Cooper STT Pros on the stock wheel and have the same issue getting the outer edges on the road as you mentioned previously.

I've noticed this as well on 37x12.5 Cooper STT Pros with the stock Rubicon 7.5 wheels. I'm afraid we will have early tire wear on these wheels...Oh well, and no warranty, no biggy. Are there more serious consequences of running the stock rims on 37x12.5s I should be aware of?
I ended up staying at 28 psi. I wasn’t getting a full contact patch but was pretty close. Had about 1/2” or maybe a little more not touching on each side. Still worked fine. Tires have 22k miles on them and we’re pretty even wear. I recently just switched to a 9” wide wheel and contact patch and sidewalk look much better.
 

gandk

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I ended up staying at 28 psi. I wasn’t getting a full contact patch but was pretty close. Had about 1/2” or maybe a little more not touching on each side. Still worked fine. Tires have 22k miles on them and we’re pretty even wear. I recently just switched to a 9” wide wheel and contact patch and sidewalk look much better.
I have some wheels on order, more like long backorder. I may have to find other options.
 

Halstem1

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I have some wheels on order, more like long backorder. I may have to find other options.
The stock rubi wheels do just fine. I’m bummed because I really loved the way they looked. Decided to choose function.
 

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