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What Psi should I run - Do a "Chalk Test" to determine

JL_MX

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Chalk test will get you in the ballpark.

A tread depth gauge used in 3 locations across the tread pattern will allow actual wear to be followed.
You need to measure when tires are first installed(baseline measurement) to get correct readings as some tires do have a rounded(edge) treat pattern.
Then just remeasure after 100 miles and follow/adjust from there.
I've never had an issue using this methodology since 1979 when I begun racing, matter of fact my gauge is a Goodyear from the 60's. On the track I use a infra-red temp gun and my gauge after every run to make precise adjustements as those tires cost $1100+ each.

The gauge will cost less than $5 and last forever.

BTW- I was the only member of my Viper club to wear the tires evenly until the others discovered my "method" back in 2000, after teaching them they all enjoyed proper wearing tires.
Being the youngest member back then no one wanted to listen, they are believers now.

Wow, great tip. Thanks a lot!!!
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JASPER

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what are people with JLUR actually finding to be good?
 

Dynomite1371

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37 cold is perfect on my Ruby. It's also what the door jam states.
 

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I run my 37x13.50 E-Rated Cooper STT Pro's at 27psi and still don't get a flat contact patch. Whats weird is the 37" STT Pro at 27psi feel more stable than the factory Rubi setup at 37psi(Probably the stiff sidewalls.)
 

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E is stiffer sidewall, I believe stock Rubis are C.
 

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OnlyOne

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I run about 28 in mine. KO2 37’s load range D
 

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I am running 315/70/R17 E-Rated Cooper STT Pro's. What do you think would be a good starting point for psi? I am a total Jeep newbie here so any help is appreciated. :)
 

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I am running 315/70/R17 E-Rated Cooper STT Pro's. What do you think would be a good starting point for psi? I am a total Jeep newbie here so any help is appreciated. :)
I would start at 30psi and work your way down until you get an event contact patch. Your tire pressure light will come one below 30psi, but hopefully the aftermarket has a fix for that soon.
 

TexasChick

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I would start at 30psi and work your way down until you get an event contact patch. Your tire pressure light will come one below 30psi, but hopefully the aftermarket has a fix for that soon.
Thanks! :)
 

bodam

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Under 30psi for everyday highway driving?!?
 

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TTEChris

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Under 30psi for everyday highway driving?!?
Yeah, I ran E-Rated toyos at 25psi for over 10k miles on one of my JK's. They had even wear, and never overheated on the highway. My E-Rated Cooper's at 27psi on the JL feel much more stable than the factory tires at 37psi. At that pressure they still don't have a completely flat contact patch with the chalk test.
 

bodam

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I just got 35 ridge grapplera and they inflated them to 42. They ride decent. But I might gradually drop them and test
 

mgroeger

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I never put the spare in the picture.


For 4 wheel drive vehicle
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I think using the spare is wisest for a few reasons...
- Even though you will need to buy 5 tires instead of 4, you will go much longer before needing to replace the tires.
- When it comes to buying new tires you won't be that guy who has 4 matching tires and a totally different spare (unless of course you buy the same brand tire every time)
Just my opinion :) Here's a chart, similar to above and simply pops the spare at a safe place in the rotation. ALWAYS take the rears straight to the front in any rotation.

upload_2018-4-10_11-14-40.png
 

PaPasJP

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I run my 35" Ridge Grapplers at 26 and they wear great and the ride is a lot better. They warm up to 28-29 after a few miles and stay there.
 

bodam

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I lowered my Ridges to 35 tonight, down from 45 from th tire shop.
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