Airing down discussion

freedom_in_4low

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Sep 26, 2019
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141
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Colorado Springs
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

Over Analizer Extraordinaire...............
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Dec 12, 2015
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In the hills of WA
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

TJ Addict
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Mar 31, 2017
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1,194
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Central California, CA, United States
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

New Member
Joined
Apr 29, 2019
Messages
13
Location
Michigan
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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Apr 15, 2019
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910
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Challis, ID
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.
 
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vinsanity

Breaker of things. Sometimes fixer of things.
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Jan 6, 2020
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Portland, OR
10-12 psi on my old 35x12.5R15s on 8" wheels and on my 40x13.5R17s on 10" wheels. Never lost a bead.