Airing Down

05 Blue Unlimited

05 Blue Unlimited

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Guys,
I finally got around to taking some local advice (Barney Brothers Off-Road) and purchased a compressor so that I can air up after I air down to get a smoother ride on the trail. I just did Ophir and Engineer Passes and noticed a BIG difference in just dropping to 20 psi. How low is safe without the worry of popping a bead?
 
20 psi is just fine. If I remember correctly, @Jerry Bransford was saying you generally don't have to worry unless you're under 12 psi.

Correct me if I'm wrong Jerry, I've never ventured that low (yet).
 
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Depending on circumstances and tire / wheel size, my experience is airing down starts to work well in the 8 -12 psi range. The caveat is that you can tear a set of tires up pretty fast at those pressures if you're a fast mover.
 
05 Blue Unlimited said:
Guys,
I finally got around to taking some local advice (Barney Brothers Off-Road) and purchased a compressor so that I can air up after I air down to get a smoother ride on the trail. I just did Ophir and Engineer Passes and noticed a BIG difference in just dropping to 20 psi. How low is safe without the worry of popping a bead?
Click to expand...
Few experienced offroaders would consider airing down to 20 psi as really being aired down. At least it's not low enough to help much. Below 15 psi is where the benefits of airing down start.

I had a newish Rubicon on the trail with me in a large group years ago and the trail could be considered "moderate" in terms of difficulty. The Rubicon was having a LOT of trouble even with both lockers engaged and was causing the group to have to stop a lot to help him. His tires were spinning way too much for conditions. I finally got him to roll down his window to ask him what pressure his tires were aired down to. He was angry by this time & gave me a pretty "huffy" answer of "WAY DOWN" and promptly rolled his window back up so the A/C could keep them comfortable on the moderately warm day.

Several minutes later, I pushed harder for an actual PSI answer and he then angrily said "all the way down to 20 psi". He and his wife were both angry because they felt the trail was too difficult due to how much trouble they were having. We were all aired down to nothing higher than maybe 12-13 psi, I was probably at 8-10 psi with my 35's. I finally got in his face and told him that is 20 psi was why he was having trouble and that we needed to get his 31" tires down to 12-13 psi so he'd stop having trouble. After pretty much going berserk at hearing our suggested air pressure, about 10 of us surrounded him and convinced him it was ok, that his tires wouldn't pop a bead, and that to continue on we "insisted" he air down more. We finally got him aired down to 12 psi & he had no more troubles the rest of the day. He & his wive finally relaxed & started having a little fun.

The moral of that story was to not be afraid to air down enough. Even a stock size Jeep tire can be safely aired down to 12-13 psi without worry. In 20 years of offroading TJs, I've yet to have any of my tires from 30" to 35" ever unseat... not even once... for any reason.
 
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There is no magic number; it varies by tire width versus wheel width, sidewall rigidity, etc. I previously aired down to 8 psi on my 35x12.5x15 tires on 8" wheels. I could do this and never walked off the rim because of the rigidity of my Cooper Discoverer STTs. I wanted to go down even further (3-4 psi) and now have beadlocks in place to ensure I don't walk off the rim.
 
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Thank you guys for all the input. For now with the way I wheel, airing down is purely for comfort. I thought 15 (until I get more experience there) would be safe and would greatly increase the ride comfort...35 to 20 sure did. Oh I am running stock 31's.
 
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resurrecting an old thread, because I'm too lazy to start a new one. (y)
Anyway, I have Cooper Discoverer AT3 XLT ~~~33-12.50 R15LT and just got a airdown kit and a Viair 450p-Rv compressor. We are at KOFA National wildlife something-or-other in Az, and we are going to go on, what most of you would call a dirt road, to us amateurs its "offroad" ( hey we have to start somewhere, right) what can I safely air down to without worrying about popping a bead, 'cause we ain't got no spare. I do have a tire repair kit
Some of you can go down to 5psi, but these trail's are hard packed, washboard. So I was thinking 20psi to start and if necessary I can drop to 15 just to make the ride a little more comfortable for the old lady ( yes, I WAS an long time biker ~~~was )
Thoughts?????
 
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10 psi easy.

On roads like that you want comfy, and especially for your lady.

5 years wheelin hard trails, rock crawling, mud, highways at 50mph, never lost a bead.
 
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Jmac00 said:
resurrecting an old thread, because I'm too lazy to start a new one. (y)
Anyway, I have Cooper Discoverer AT3 XLT ~~~33-12.50 R15LT and just got a airdown kit and a Viair 450p-Rv compressor. We are at KOFA National wildlife something-or-other in Az, and we are going to go on, what most of you would call a dirt road, to us amateurs its "offroad" ( hey we have to start somewhere, right) what can I safely air down to without worrying about popping a bead, 'cause we ain't got no spare. I do have a tire repair kit
Some of you can go down to 5psi, but these trail's are hard packed, washboard. So I was thinking 20psi to start and if necessary I can drop to 15 just to make the ride a little more comfortable for the old lady ( yes, I WAS an long time biker ~~~was )
Thoughts?????
Click to expand...
You can try 20 see how it rides, let more out if you want it softer. It sounds more like a higher speed road. Remember when you air down watch the corners if you are at speed.
 
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NskLJ said:
You can try 20 see how it rides, let more out if you want it softer. It sounds more like a higher speed road. Remember when you air down watch the corners if you are at speed.
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oooh, didn't think of that turn shit at speed, good call, but we are here to 'site-see' not really blow down the trails, we want to get out to a place called "Skull rock", its on google maps. looks like it might turn into a little bit of a hike, but Einstein could use the exercise LOL

EinsteinGlasses.jpg
 
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Jmac00 said:
resurrecting an old thread, because I'm too lazy to start a new one. (y)
Anyway, I have Cooper Discoverer AT3 XLT ~~~33-12.50 R15LT and just got a airdown kit and a Viair 450p-Rv compressor. We are at KOFA National wildlife something-or-other in Az, and we are going to go on, what most of you would call a dirt road, to us amateurs its "offroad" ( hey we have to start somewhere, right) what can I safely air down to without worrying about popping a bead, 'cause we ain't got no spare. I do have a tire repair kit
Some of you can go down to 5psi, but these trail's are hard packed, washboard. So I was thinking 20psi to start and if necessary I can drop to 15 just to make the ride a little more comfortable for the old lady ( yes, I WAS an long time biker ~~~was )
Thoughts?????
Click to expand...
20 psi is not really even airing down, you need to be at least below 15 for it to really help. I had a guy on a medium-difficult trail in a shiny nearly new Rubicon and he was having a hell of a time, enough that he was holding up the entire group of 15+ Jeeps, a club I was in at the time. I hopped out to spot him (again) and noticed all his tires were slipping and spinning, he was obviously not aired down enough because none of the rest of us was having that problem. I went up to his window to ask him what his air pressure was... he had to roll it down because he and his wife were wheeling in air conditioned comfort.... it was a hot day. He rolled it down only a few inches, which I thought was odd, and asked him what PSI he had aired down to. He was clearly angered by my question and snapped back "enough" and rolled his window back up. This went on another time or two until I finally got 20 psi out of him. Not even close to being aired down. It took 3 or 4 of us to convince him that his tires would not unseat if he would just air down to 12 psi. He finally (angrily) did and from that point forward he had no problems. And we never saw him again in another club run. It was clear he did not enjoy what we were doing lol.

The moral of that story is airing down enough is important and trust us when we say that you're not going to lose a tire bead by being at 10-12 psi, though even 15 psi will help both traction and comfort on easier trails. And added traction is the main benefit to lower tire pressures, added ride comfort is just a side benefit. :)
 
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I did several "paint" tests on my tires (jack up a tire, paint the tread, set it down carefully on a piece of paper, jack it back up). The tread prints showed that there was almost no difference in the contact patch between normal pressure and 20 PSI. The contact patch only started getting decently bigger when I got them down to 15 PSI.

Question: What do you plan to air up to after you're done? 25-26 PSI is about right for 33" tires for the highway.
 
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OldBuzzard said:
I did several "paint" tests on my tires (jack up a tire, paint the tread, set it down carefully on a piece of paper, jack it back up). The tread prints showed that there was almost no difference in the contact patch between normal pressure and 20 PSI. The contact patch only started getting decently bigger when I got them down to 15 PSI.
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Tire footprint (2).jpg
 
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OldBuzzard said:
I did several "paint" tests on my tires (jack up a tire, paint the tread, set it down carefully on a piece of paper, jack it back up). The tread prints showed that there was almost no difference in the contact patch between normal pressure and 20 PSI. The contact patch only started getting decently bigger when I got them down to 15 PSI.

Question: What do you plan to air up to after you're done? 25-26 PSI is about right for 33" tires for the highway.
Click to expand...

Cooper Tire recommends a MAX cold air pressure of 40psi. I usually run them around 32-35
 
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