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-   -   Tire Pressure Question (http://www.wranglerforum.com/f282/tire-pressure-question-48817.html)

bpm54 04-14-2010 12:10 PM

Tire Pressure Question
 
I had the tires replaced on my newly purchased 04 Rubicon. The tires are Goodyear Wrangler MTR LT245/75R16, same as the old ones. I checked the tire pressure and they are at 42psi. The tire pressure label on the door panel states the pressure should be 33psi.

To me that seems low for the tire size. Which one is correct?

JDsDream 04-14-2010 12:21 PM

I run 31x15's and keep them at 28psi. Not sure what is appropriate for your tire size. One way to check is to do a chalk test. draw a line across (from side wall to side wall) with chalk. Roll over the chalk and see what parts of the tire are actually making contact. Adjust the pressure until you have equal contact all the way across the tread.

03 RUBI 04-14-2010 01:05 PM

The door panel pressure is the "correct" one depending on load, but do as JD suggests just to double check.

IslandTJ 04-14-2010 01:37 PM

That's too high, I run 26-28 psi in my 33x10.5" tires when I don't off-road.

Jerry Bransford 04-14-2010 01:38 PM

Quote:

Originally Posted by bpm54 (Post 598186)
I had the tires replaced on my newly purchased 04 Rubicon. The tires are Goodyear Wrangler MTR LT245/75R16, same as the old ones. I checked the tire pressure and they are at 42psi. The tire pressure label on the door panel states the pressure should be 33psi.

Whoever filled them to 42 psi is an idiot. Your tire is equivilent to a 31" size tire and 31 is fine for normal street driviing. 33 psi is only for when your Rubicon is fully loaded with passengers & gear. :)

adawg38 04-14-2010 01:45 PM

I go by the PSI recc on the door jam as long as it matches the tire size you got. changing what the manufacture recc changes gas mileage, tire wear and sometimes the ride feel. Some of these tire shops like to put whats on the sidewall of the tire which is max pressure. If you go bigger you need to adjust the pressure up a bit. I left 33psi in my 245/75R16's for a long time and never had issues.

04tjrubicon 04-14-2010 01:46 PM

20 on 37x12.5x17

Atthehop 04-14-2010 01:57 PM

Chalk them then you will not have to guess.

jdhallissey 04-14-2010 01:58 PM

HAAHHAHA right now I am at 8psi and did a 40 mile road trip the other day to the golf course. Thing DROVE AND RODE like a absolute dream. A lot of side wall that is soft will eat the bumps lol. Tho my gas mileage suffered from it. I run my 33's right around 25-27 psi. I can run them higher normally do if I am driving it to go off-roading, you get better gas mileage when they are really full. Less surface area touching the ground equals less friction equals well you get the point.

Jerry Bransford 04-14-2010 01:59 PM

Quote:

Originally Posted by adawg38 (Post 598281)
I go by the PSI recc on the door jam as long as it matches the tire size you got. changing what the manufacture recc changes gas mileage, tire wear and sometimes the ride feel. Some of these tire shops like to put whats on the sidewall of the tire which is max pressure. If you go bigger you need to adjust the pressure up a bit. I left 33psi in my 245/75R16's for a long time and never had issues.

Go check your door jamb's air pressure sticker and you will discover it gives two different air pressures for each possible size tire... like "31/33 psi". The 31 psi is for how the Jeep is normally driven with 1-2 people, not fully loaded. The second air pressure, like 33 psi, is only for when it is fully loaded to its max recommended weight for all seats occupied & gear in the back. :)

adawg38 04-14-2010 02:06 PM

Quote:

Originally Posted by Jerry Bransford (Post 598295)
Go check your door jamb's air pressure sticker and you will discover it gives two different air pressures for each possible size tire... like "31/33 psi". The 31 psi is for how the Jeep is normally driven with 1-2 people, not fully loaded. The second air pressure, like 33 psi, is only for when it is fully loaded to its max recommended weight for all seats occupied & gear in the back. :)

I'll double check but I only recall seeing the pressure saying 33psi Cold. If that's the case I don't have a prob dropping it down a bit might make the ride a little softer.:punk:

Jerry Bransford 04-14-2010 02:10 PM

Trust me, your stiff riding E Load Range MT/Rs can safely run 31 psi. The particular size MT/R Jeep chose for the Rubicon only came in an E Load Range which is actually meant for a much heavier vehicle than the Wrangler is.

Most of the other sizes of MT/Rs like my 35x12.50 MT/Rs are C Load Range rated which is much better riding yet still a little higher rated than the TJ actually needs. The E Load Range carcass is much stiffer than is required for a vehicle with the weight of a Wrangler so no worries about 30-31 psi. :)

adawg38 04-14-2010 02:20 PM

Not trying to hijack the thread but I swapped my 245's for 31's. is 30-31psi good there also?

oakdale bob 04-14-2010 02:28 PM

Tire pressure???
 
I'm really confused!!! I just put oversized tires & wheels on my '10 wrangler, and the tire pressure light does not go off. I thought the tire pressure to use is what is stamped on the tire, or should I use the tire pressure on the door jam, even though it's for smaller tires??? Thanks, Bob-:banghead:

Jerry Bransford 04-14-2010 02:30 PM

Quote:

Originally Posted by adawg38 (Post 598318)
Not trying to hijack the thread but I swapped my 245's for 31's. is 30-31psi good there also?

Those are essentially both 31" size tires so you can run the same air pressure with 30-31 being fine. :)

adawg38 04-14-2010 02:33 PM

Quote:

Originally Posted by oakdale bob (Post 598327)
I'm really confused!!! I just put oversized tires & wheels on my '10 wrangler, and the tire pressure light does not go off. I thought the tire pressure to use is what is stamped on the tire, or should I use the tire pressure on the door jam, even though it's for smaller tires??? Thanks, Bob-:banghead:

Do you still have the stock wheels on there? Try retraining your tire sensors, look in the owners manual that should help.

oakdale bob 04-14-2010 02:39 PM

Tire Pressure
 
I went to 17" wheels, and larger tires. Les Schwab did the conversion. The book says " drive it, they'll reset themselves. I've driven it about 50- miles, no change. ANY suggestions??? Thanks, Bob-:banghead:

mrcarcrazy 04-14-2010 02:39 PM

when in doubt do a chalk test. run the max. air pressure you can while keeping all the tread in contact.

As stated above 30psi is a safe number. and its easy to remember.

adawg38 04-14-2010 02:46 PM

Quote:

Originally Posted by oakdale bob (Post 598340)
I went to 17" wheels, and larger tires. Les Schwab did the conversion. The book says " drive it, they'll reset themselves. I've driven it about 50- miles, no change. ANY suggestions??? Thanks, Bob-:banghead:


not sure. Did they reinstall the tire sensors in the new wheels or just put regular valve stems in? I haven't worked for Chrysler for a little over 4 years but back then all the sensors had to be retrained manually. If they did do the swap drive her for a bit longer just to be sure. Or maybe go into your menu options and see if you can turn off the tire sensors.

adawg38 04-14-2010 02:47 PM

Quote:

Originally Posted by bpm54 (Post 598186)
I had the tires replaced on my newly purchased 04 Rubicon. The tires are Goodyear Wrangler MTR LT245/75R16, same as the old ones. I checked the tire pressure and they are at 42psi. The tire pressure label on the door panel states the pressure should be 33psi.

To me that seems low for the tire size. Which one is correct?

So I would go by what Jerry's saying. He seems respected here by a lot of people and he's got my trust.

oakdale bob 04-14-2010 03:01 PM

Thanks, I'll give it a shot. (by the way, GOOD LOOKING dog, sure miss mine) Bob-:(

birdhunter 04-14-2010 03:46 PM

Start at 30 and go up or down a few PSI
To get the ride your after

Logans Run 04-14-2010 03:51 PM

Quote:

Originally Posted by birdhunter (Post 598390)
Start at 30 and go up or down a few PSI
To get the ride your after

Completely agree. I have 33x10.5 and run 35psi on the street and 14psi offroad. any place in between is fine. But I would suggest closer to 30-35psi on the highway so you don't slip a beed going to fast.

bpm54 04-14-2010 03:55 PM

Ok, all very helpful. Obviously they are too much inflated at 42 and yes they are E rated and don't have a max psi # listed on the sidewall.

I'm going to give them the chalk test at the present psi just to see how much tread isn't connecting and then drop them from there.

Thanks!

Jerry Bransford 04-14-2010 05:09 PM

Don't over-analyze this and realize that for most people, relying solely on the chalk test often results in an under-inflated tire. So don't get into analysis paralysis on this, you'd be fine with 31 unloaded and 33 loaded.

And Logans Run, you don't need 30-35 psi to prevent a 33x12.50 tire from losing its bead going too fast. 26-28 psi is all that is needed for that size tire. And to add a little backup on that, I run 8 psi all the time with my 35x12.50 tires on 15x8 wheels when on harder rock crawling trails. And guess what, I've never lost a bead even at that low of a pressure. I'm not saying it can't happen but I'm saying that you don't need 30-35 psi on the street for a 33x12.50 tire either.

It seems the newer the Jeeper, the more tire pressure he is convinced that he needs. :)

03 RUBI 04-14-2010 07:28 PM

Quote:

Originally Posted by bpm54 (Post 598397)
Ok, all very helpful. Obviously they are too much inflated at 42 and yes they are E rated and don't have a max psi # listed on the sidewall.

The PSI listed on the sidewall is the MAXIMUM pressure for that tire, not what you should be running them at!

IslandTJ 04-14-2010 09:54 PM

Quote:

Originally Posted by Logans Run (Post 598393)
Completely agree. I have 33x10.5 and run 35psi on the street and 14psi offroad. any place in between is fine. But I would suggest closer to 30-35psi on the highway so you don't slip a beed going to fast.

I also run 33x10.5 on a 15x8 wheel and have taken my Jeep up to freeway speeds safely. My normal psi is 28psi. The tires and Jeep never feel unsafe.

When I off-road, I run the following psi range without issue and haven't lost a bead:

Typical off-road conditions: 12psi
Wet & muddy: 10psi
Snow: 8psi

bpm54 04-14-2010 10:28 PM

Just dropped them all down to 33 psi. I ride tomorrow. I'll follow up as to quality of ride to work. I commute 40 miles a day with this jeep now.

Kohrs93 04-14-2010 10:38 PM

I run mine at 31 on road. off road i drop to 15 or lower depending on the conditions.

bpm54 04-14-2010 10:55 PM

15! holy crap! Any suggestions for tire pressure for beach jeeping? And, it looks like, I will need to invest in a good tire inflator or compressor...


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