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Airing down discussion


freedom_in_4low

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Remember that a tire's advertised width is only its widest width half-way up the sidewall which can be up to several inches wider than its mounting beads. A 33x10.50 tire, for example, will probably have beads that are only 7 or 8" apart which is why you should run a 15x7 or 15x8 wheel for a 10.5" wide tire. Trying to run a 33x10.50 tire on a 15x10 wheel, for example, would result in the tire being forced to position its mounting beads much further apart than they were designed for.
I'd love to hear/read this attacked from another angle, which is how much farther might a 12.5 be able to air down than a 10.5 in the same model of tire, both on a 15x8 wheel. Is it "narrower the wheel, the better" (within reason) or is it more like once it's within the range the tire was designed for, it's enough?
 

Wildman

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I can relate to being "NEW" to wheeling and the idea that I needed to air down. Back in 1992 I had a YJ that I had lifted and was running 33x12.5x15 Geolander tires. I went to a CA4WDA Wheelin 101 class at Hollister Hills ORV park and was having all kinds of issues climbing this one section of trail. One of the people doing the class asked me how much I was aired down to and I said with all kinds of PRIDE in my voice "15PSI". Well I was worried about popping a bead and didn't know better. She explained to me that if I would drop my pressure to 10-12PSI I would have much better results. Of course being the "DUMBASS" Army guy I didn't listen at first. But after being asked and told by a few others I finally listened. Dropped down to 10 PSI and boom I walked right up that section of trail.

Fast forward to 2005 when I got my first set of beadlocks. Prior to having them I had some 12" wide wheels that had come on my TJ when I bought it. Those rims had some 33x14x15 TSL Bogger tires and if I went below 12 PSI I'd pop a bead left and right.

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When I came back from Iraq one of the first things I bought was Allied beadlock rims. Had a little help mounting up all 5 tires onto the rims.

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I don't have a lot of pictures with these times aired down.

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Then I got this WILD HAIR and decided I wanted to run dual beadlocks like the military Hummer rims. So I bought some used rims and recentered them and installed 38x12.5x16.5 TSL SX tires. First time out was a snow run and just to see how low I could go I took them down to 2 PSI and never had any issues. Now these are not for the weak back folks since the tire and wheel combo weighs in at 138lbs each.

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2 PSI

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xxdabroxx

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33x12.5x15 on 8" rim:

Rocks: 8psi

One of the last snow trips I made I was aired down to 8psi. I feel like for snow on smooth roads I could go lower and my try 6-7 next time out. I'll probably try 7psi next time I'm in the sand as 8 didn't look that smooshed in sand.

However I did get a little feathering on the outside lugs of my tires after driving quite a ways on the pavement to get to a good spot to air back up after. I put probably 20 miles on them after getting back to dry pavement. It's nothing major but there are some strange spots of wear now. I figure it will wear off in the next few thousand miles.
 

j8014

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33x12.5x15 15x10

Depends on the terrain. Ive never popped a bead but I have had roots and gravel pressed into the rear rim/tire and give me a flat at 12 psi, multiple times climbing out of the steep sandy ravines shown below.

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reddvltj

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The lowest I ever dropped pressure was on a snow run before I had lockers and there was a hill that everyone was struggling to make it up. The leader of the run walked back to me and asked me if I wanted to try it without winching. I said sure, his next comment caught me completely off guard. "Give me your valve stem cores!" I thought he was joking, but he wasn't. I asked him about losing a bead and he responded it's a possibility, but we had enough people with OBA to get it re-seated if that happened. I was running 33x12.50x15 SSR (Super Swamper) radials on 8" ultra aluminium wheels. We pulled the cores out and until after the air stopped then put them back in. I drove up the hill without incident, got to the top and we aired my tires back up to about 3 pounds and I finished the run (about 6 hours later) without ever losing a bead.
 

vinsanity

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10-12 psi on my old 35x12.5R15s on 8" wheels and on my 40x13.5R17s on 10" wheels. Never lost a bead.
 

Captain Phoenix

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On 285/75R16 KO2s would I be safe driving the 25 miles each way to and from the beach at 15 PSI? It's mostly city driving so maybe 55-60 top speed and never for very long at a time. Usually more in the 35-45 mph range.
 

pagrey

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On 285/75R16 KO2s would I be safe driving the 25 miles each way to and from the beach at 15 PSI? It's mostly city driving so maybe 55-60 top speed and never for very long at a time. Usually more in the 35-45 mph range.
I'd do it. If you are at all worried, stop the Jeep in a safe place and put your hand carefully on the sidewall. If anything is wrong you'll know real quick.
 

jodomcfrodo

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When I was in Moab my tires stayed at 12 for the whole week, driving around at up to 70 mph. No problems.

My passenger rear tire measured 13 psi a couple days ago. Must’ve gone down over the winter while the Jeep was sitting, never noticed it. I’ve been cruising around town just fine for the last few days, not worried about it at all. Just need to find some damn quarters so I can go air it up.
 

Mobusaki

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I run my 265/75r16 (32") load range C at 10-13 psi. My Duratracs are soft and have a lot of squish at those pressures. Have not lost a bead yet, but I did have some debris get between into the bead and cause a slow leak.

A question to those who air down. Who gets asked about your tire pressure?

This happens to me very often as I pass others on the trail. I don't know if this happens to others in our group. Most are visibly surprised when I say 8psi. I don't know what causes them to ask the question.
Occasionally. Usually I'm the one asking others because no one I wheel with ever looks aired down, even after "airing down" before a run. No one I have asked has ever said anything lower than 15 psi. Sometimes they are at 18 psi. A lot of them are on 35's and lockers so they still get around fine. Most of them are on load range E (I feel like that's all the JK guys use).

All that said, the best wheeler I know runs his YJ on 33's at 15 psi and his tires don't look aired down at all. No squish. They may even be load range E. He makes me doubt the whole airing down until your tires "squish" thing, but it works so well for me and you all recommend it so I keep doing it. I do wish I could instantly add more air to my tires when we come to ruts made by 35"+ tires. I always drag my diffs through that.
 

Garza

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I have ran 6psi on 35", 37", 40", and 42" for say 15+ years now in the rocks (yes all on beadlocks). I believe I did see it mentioned earlier, but airing down is more knowing what your brand/style tire works at, on your rig, in what terrain you are on. No one believes me when I tell them the difference between making a line and not can be 1-2psi drop in air pressure. Most people wheel with too much air, hell most people daily drive with too much air LOL. And I recheck several times throughout the trail....if mine get to 8 or 9psi, they don't work!
 

Jerry Bransford

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I have ran 6psi on 35", 37", 40", and 42" for say 15+ years now in the rocks (yes all on beadlocks). I believe I did see it mentioned earlier, but airing down is more knowing what your brand/style tire works at, on your rig, in what terrain you are on. No one believes me when I tell them the difference between making a line and not can be 1-2psi drop in air pressure. Most people wheel with too much air, hell most people daily drive with too much air LOL. And I recheck several times throughout the trail....if mine get to 8 or 9psi, they don't work!
Absolutely X2 to all that! I'm always seeing people on the trail whose tires weren't aired down nearly enough and they're spinning their tires with a lot of problems on even easier parts of the trail. Sometimes it's a difficult thing to get them to air down enough but if/when they do they're amazed that 1) their tires didn't fall off and 2) that they had a much easier time on the trail afterward.
 

Flivver250

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I let the air out for dune smashing, and since my last post on this thread I did break the bead on a tire. Foot to the floor, sliding sideways up a dune, my fault. Not a big deal, I carry a pump. I was at 5lbs. When I camp in the desert, I absolutely can't move with my loaded trailer if I have 15-20 pounds. Lower to 5-10 and it pulls the trailer like it is not there. No effort. I now only lower to 10lbs when I'm in the dunes and it is okay. BTW, not all sand was created equally.
 

Mobusaki

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I have ran 6psi on 35", 37", 40", and 42" for say 15+ years now in the rocks (yes all on beadlocks). I believe I did see it mentioned earlier, but airing down is more knowing what your brand/style tire works at, on your rig, in what terrain you are on. No one believes me when I tell them the difference between making a line and not can be 1-2psi drop in air pressure. Most people wheel with too much air, hell most people daily drive with too much air LOL. And I recheck several times throughout the trail....if mine get to 8 or 9psi, they don't work!
That's so true. I know people who "air down" to 15-18 psi and then air back up to 35+ psi for the road. I'm on 32's at 28-29 psi on the road... how are you guys on 35's at 35 psi? :ROFLMAO:

The photos posted earlier show the different a small drop in air pressure will make once you are in the low teens and single digits. They also give an idea of how much ground clearance you may be losing. I measured how much ground clearance I lost between 15 psi and 10 psi but I didn't write it down. I think it was about 1/2", which is significant. That's like going down a tire size.

I would like to start out at ~15 psi (unlike my wheeling companions my load range C duratracs tires are fairly squishy at this point) to retain some ground clearance and then air down more if needed later, but I don't think those load range E JK guys at 18 psi would understand why I'm bothering to air down even more in the middle of the trail, so I just go low from the get go.
 

Mobusaki

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I let the air out for dune smashing, and since my last post on this thread I did break the bead on a tire. Foot to the floor, sliding sideways up a dune, my fault. Not a big deal, I carry a pump. I was at 5lbs. When I camp in the desert, I absolutely can't move with my loaded trailer if I have 15-20 pounds. Lower to 5-10 and it pulls the trailer like it is not there. No effort. I now only lower to 10lbs when I'm in the dunes and it is okay. BTW, not all sand was created equally.
That's something I've not thought about. Do you air down the trailer tires also?
 

xxdabroxx

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That's so true. I know people who "air down" to 15-18 psi and then air back up to 35+ psi for the road. I'm on 32's at 28-29 psi on the road... how are you guys on 35's at 35 psi? :ROFLMAO:

The photos posted earlier show the different a small drop in air pressure will make once you are in the low teens and single digits. They also give an idea of how much ground clearance you may be losing. I measured how much ground clearance I lost between 15 psi and 10 psi but I didn't write it down. I think it was about 1/2", which is significant. That's like going down a tire size.

I would like to start out at ~15 psi (unlike my wheeling companions my load range C duratracs tires are fairly squishy at this point) to retain some ground clearance and then air down more if needed later, but I don't think those load range E JK guys at 18 psi would understand why I'm bothering to air down even more in the middle of the trail, so I just go low from the get go.
You should really try going lower right off the bat. If you are worried 11-12 is a VERY safe psi for most tire/wheel combo's within reason. Get down to 8-10 and the ride on small rocks is much softer and the grip on larger ones is much better as well. In snow or sand you can go even lower safely so long as you aren't carving corners at high speed.
 

Flivver250

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Something I have discovered, When you lower the air and go dune smashing, you do have to balance the wheels more often. I think it is probably the wheels can change where they sit on the tire. The cost of doing business.