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Old 04-28-2013, 12:36 AM   #1
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Tire pressure, when and what...

Hello I'm heading out on a few medium rated trails soon and wanted to know when I should lower tire pressure and what pressure should I run? I would assume only when driving over rocks I would need to deflate and I've heard, read 25 lbs. Can anyone give me guidance?

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Old 04-28-2013, 01:06 AM   #2
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The lower psi helps in any kind of terrain not just rocks.Depending on what tire and wheel to what you would want to lower too. I air down my 33' Duratracs to 25- 28 for trail use.

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Old 04-28-2013, 08:54 AM   #3
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When I drive over mainly rock I air down to 10-12 psi. Most other time on variable terrain (some rock, mud and sand) I go to 18-20psi. I have 35" MT tires.
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Old 04-28-2013, 10:23 AM   #4
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I run my 35 inch Duratracs at 28 on the street and 18 on the trails. Lowering pressure while off-roading allows your tire to soak up some of the bumps and puts less wear and tear on equipment and people.
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Old 04-28-2013, 10:25 AM   #5
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As long as you don't have 10" wide wheels go down to 15# or lower or don't bother. Try it, see the difference it makes, people are amazed when I have them do it. At the sand dunes in MI they won't let you go out unless your 15# or lower.
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Old 04-28-2013, 10:37 AM   #6
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33's

I run the BFG Mud Terrain TA KM2's. They are 33's. I run 32lbs on the highway and 18lbs when off-road.
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Old 04-28-2013, 10:49 AM   #7
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I wouldn't consider going down to 25# airing down, no matter what size tire it is. Like someone said earlier you don't air down only for traction, it is also done to make the ride way smoother. 16/18# should be a good number for yah.
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Old 04-28-2013, 02:12 PM   #8
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28 on the highway with 35" MTRs (30-32 with my stock 32 KMs). Off road, I used to air my KMs down to around 16-18 but it has soft sidewalls. With the MTRs, I will probably stay around 12. Dirt roads- probably 18.
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Old 04-28-2013, 02:34 PM   #9
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what should stock '13 rubicon wheels be aired to for beach/sand?

i think it came from the dealer at 40
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Old 04-28-2013, 06:03 PM   #10
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I wouldn't consider going down to 25# airing down, no matter what size tire it is. Like someone said earlier you don't air down only for traction, it is also done to make the ride way smoother. 16/18# should be a good number for yah.
Thank you, I will be trying this on the trip and bringing a compressor
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Old 04-28-2013, 07:18 PM   #11
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From one of the offroading mags I read once to get the optimum offroad air pressure, you should inflate your tire to the manufactures stated air pressure. Then measure from the bottom of the wheel to the ground. Example 6". Then deflate the tire to 75% of that number so using the example it would be 4.5". That doesn't seem to be low but depending on the sidewall stiffness it will be somewhere between 6 and 15 PSI with stiffer tires at the lower psi side. Saying that they don't recommend less then 8 psi unless you have beadlocks so not to loose seal while on the trail.
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Old 04-28-2013, 07:23 PM   #12
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40 is ridiculous...and probably dangerous. First go to 32-32 on the street. I think for sand, you could go to 20 psi or even lower if you want more floatation in deep sand. The KMs have compliant sidewalls.

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what should stock '13 rubicon wheels be aired to for beach/sand?

i think it came from the dealer at 40
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Old 04-28-2013, 08:14 PM   #13
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the EVIC shows em at 40 PSI, i figured that was normal for street ... no?
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Old 04-28-2013, 08:23 PM   #14
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the EVIC shows em at 40 PSI, i figured that was normal for street ... no?
I had the same experience. When i got the new Duratracks 285/70/17 on my new 2013 wrangler OscarMike, Discount Tire dealer installed the tires at air pressure was 39-40 psi. I noticed that when jumped in the car to drive back home and the service guy refused to take it down to 34... So i took it down to 34 but it was still a bit too bumpy and now i run it at 31-32 on street conditions and at the trail down to 20-22
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Old 04-28-2013, 08:49 PM   #15
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i don't mind it, should i drop it to 37 see how it feels? i am assuming they fill it to 40 for the MPG?
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Old 04-28-2013, 09:19 PM   #16
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@ 40 psi u r probably gonna have bad wear. 31-32 is ideal. Ya ur mpg dropa very slightly but ur tires will last a lot longer and ur ride will be nicer.

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Old 04-28-2013, 09:33 PM   #17
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Originally Posted by dalearyous View Post
what should stock '13 rubicon wheels be aired to for beach/sand?

i think it came from the dealer at 40
Silver Lake sand dunes state park in Michigan won't let you out of the parking lot and onto the dunes unless go to 15# or lower.
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Old 04-28-2013, 10:32 PM   #18
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Silver Lake sand dunes state park in Michigan won't let you out of the parking lot and onto the dunes unless go to 15# or lower.
do they have people checking your tire pressure?
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Old 04-30-2013, 09:48 AM   #19
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They do have an inspection station. I don't know how hard they check it. I can usually tell by looking if you've aired down in to the mid teens by looking.

I see it all the time, one jeep makes obstacle no problem, next jeep same or better build has trouble. Difference was PSI in the tires, air down the jeep having trouble to 12 to 15# and it's like a different jeep.
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Old 04-30-2013, 09:55 AM   #20
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I usually aired down my stock Dueler AT (stock Sahara rim and tires) to about 22 PSI, and I liked it much more, but I was wondering where's the safest low point I can go with these rims and tires? I'm heading to a rocky/sandy/muddy park on saturday and want to go down as much as I can.
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Old 04-30-2013, 11:57 AM   #21
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the EVIC shows em at 40 PSI, i figured that was normal for street ... no?
The door sticker (applicable for stock tires) I think says 35PSI. That said mine are now at 40PSI because I last filled them when it was 25F outside and it's now 70F. I agree 40 isn't safe, the handling feels a bit loose. However I get an extra 1-2MPG's.
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Old 04-30-2013, 12:02 PM   #22
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I usually aired down my stock Dueler AT (stock Sahara rim and tires) to about 22 PSI, and I liked it much more, but I was wondering where's the safest low point I can go with these rims and tires? I'm heading to a rocky/sandy/muddy park on saturday and want to go down as much as I can.
You can do 12/13 psi safely
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Old 04-30-2013, 12:08 PM   #23
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@ 40 psi u r probably gonna have bad wear. 31-32 is ideal. Ya ur mpg dropa very slightly but ur tires will last a lot longer and ur ride will be nicer.

Bryce
Both the dealer and the tire supplier bumped me to 40 on my Goodyear SilentArmors from 37 on the door. Better mileage and car handles better. Tire dealer wouldn't do that if it was wrong inflation resulting in bad wear pattern. Will probably drop to 25 offroad- I don't want to have a tire come off the rim.
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Old 04-30-2013, 12:31 PM   #24
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I'm still on stock Sport S (Goodyear Wrangler SR/A) tires. The placard on my door says 35 - I find 32 more comfortable on the road. I air down to 20 when wheeling. Well, I target 20, sometimes one is at 18, another 19, etc. I don't fret about it. Watch carefully how long and how fast you go if you are still at trail pressure and you need to drive on pavement. Around here we typically have pavement time in between trails, and it isn't practical to keep switching back and forth during a run - I won't go over 40mph when I'm aired down, and prefer to keep it under 35mph.
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Old 04-30-2013, 01:31 PM   #25
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40 psi will very likely lead to abnormal wear, and will lead to bad and dangerous handling- especially in wet/snowy conditions. However, feel free to feel they all know best. The CAFE requirements make the car manufactures also inflate PSI to get that 1 MPG extra in theory. Otherwise, these gas hogs pull their average down.
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Old 04-30-2013, 02:08 PM   #26
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You can do 12/13 psi safely
Last ride I took a guy running 14# had a 3" diameter ground limb just push his sidewall off the rim. Flat as a flitter a second later. Just saying.

My trail guys all hover 16-18# as guideline.
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Old 04-30-2013, 02:14 PM   #27
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Last ride I took a guy running 14# had a 3" diameter ground limb just push his sidewall off the rim. Flat as a flitter a second later. Just saying.
Odds are that this would have happened at 18 or 20 also. Or if not it could have damaged the side wall. I have seen very few tires blow a bead above 10 psi over the years unless someone was being stupid. Hell I have seen them blow at streat pressure when pushed up against rocks that stick out just right.
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Old 04-30-2013, 03:36 PM   #28
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So after all this discussion I called my Jeep dealer (they are serious offroaders) and tire supplier. Both said use the pressure stated on the door. Tire guy said you could go a little softer if you wanted. Jeep dealer said, as far as airing down, he wouldn't go below about 20 psi just for the safety factor of not damaging a rim or losing a bead. For people with extra heavy duty tires with multiple ply stiff sidewalls he would be comfortable down to 12 psi.
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Old 04-30-2013, 03:42 PM   #29
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So after all this discussion I called my Jeep dealer (they are serious offroaders) and tire supplier. Both said use the pressure stated on the door. Tire guy said you could go a little softer if you wanted. Jeep dealer said, as far as airing down, he wouldn't go below about 20 psi just for the safety factor of not damaging a rim or losing a bead. For people with extra heavy duty tires with multiple ply stiff sidewalls he would be comfortable down to 12 psi.
What tire you run does have a lot to do with it, but if you only go down to 20psi you are wasteing your time if you are doing it for any other reason then geting a smoother ride IMO. The whole idea is to let the tire deform and change shape with the trail.
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Old 04-30-2013, 04:23 PM   #30
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My new 13' JKU has 38psi according to the onboard display... At first it was on metric and those numbers meant nothing to me then I flicked it on standard and was surprised to see a truck tire at 38psi...

I have a friend who bought a new Dodge Ram and said the psi fluctuated like crazy and he had to go to the dealer for them to adjust the pressure and re-calibrate the computer or something

I think 38psi is too much and it seems most of you would agree.

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