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Old 09-02-2013, 01:23 AM   #1
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Airing down

Going offloading next weekend. I have 33 by 12.5 by 15 inch duratracs with I think a 2 ply sidewall. I want to see how much better offroad my jeep will do with my tires aired down. I have 15 by 8 soft 8 steel wheels. I was thinking 14 psi aired down and only go with a max of 20 mph while aired down. Does this sound good or should I do something different? Thanks, Joey.

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Old 09-02-2013, 01:56 AM   #2
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I have 33x12.5x15 MTR 's on mine and went to the rubicon last weekend and aired down to about 11psi. I had no problems, however I was on rocks crawling around. Towards the end of the trail it smooths out and was probably doing around 20 - 30 in the dirt with no probs. I'm no expert, just fyi. It does make a big difference in your wheelin however. Have an awesome time!

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Old 09-02-2013, 01:57 AM   #3
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Also on 15x8 wheels
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Old 09-02-2013, 12:48 PM   #4
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What are going to be encountering? Should be fine. When I aired down to about 16 I only encountered problems on a shallow creek when rubbed up against a few rocks and broke my seal.
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Old 09-02-2013, 12:54 PM   #5
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I also run 33"12.5-15 duratracs on soft 8s, I usually air down to 18-20, if you have no way to air back up you don't want to go much lower, Duratracs at 6-8 psi will spin on the rims and the sidewalls won't hold the weight, at least this is my personal experience with mine on my TJ.
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Old 09-02-2013, 12:55 PM   #6
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What are going to be encountering? Should be fine. When I aired down to about 16 I only encountered problems on a shallow creek when rubbed up against a few rocks and broke my seal.
16 psi is not a low air pressure for offroading at all, what width wheels are you running? A wide wheel makes it harder for an aired down tire to remain seated. Typical aired down no problem air pressures for that size tire are 11-13 psi.
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Old 09-02-2013, 12:57 PM   #7
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never had a problem with 33x12.5 duras at 12-14 psi, i run 10-11psi with the 35" duras and have yet to slip a bead

IMO, you arent aired down until you get below 15psi and below 12 psi is where the traction really starts
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Old 09-02-2013, 12:58 PM   #8
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Get a digital gauge, deflators and an air compressor.
I use the MV50 compressor (great little compressor) until I get my on board air installed.
I have similar tires and I run 8.5 up to 12 psi's depending on the trails. Try several different settings and see how it does. When you start getting into really low psi's then beadlocks are desirable.
We also drive 10-15 minutes to get to the trails running the low tire pressure.
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Old 09-02-2013, 02:02 PM   #9
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So just going to an offroad park where there's mud ( of which in trying to stay away from cause its a pita to clean and not much fun no skill in it really) rocks hills trails and sand just general everything. So for my setup you guys are recommending 12psi? And yes I do have a small air pump for my cigarette lighter to air up it may take a while but it will work. Any other suggestions? Thanks, Joey.
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Old 09-02-2013, 02:17 PM   #10
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12 psi is a good all-around air pressure for 33x12.50 tires mounted on your 15x8 wheels. I wouldn't trust that air pressure as much with a wider wheel like a 15x10 though.
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Old 09-02-2013, 02:21 PM   #11
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Like Jerry said the 15 x 10 rims aren't as forgiving as an 8" wide rim. Too many run rims that are too wide for their tires.
Try and find a compressor that won't take an hour to fill the tires.
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Old 09-02-2013, 02:30 PM   #12
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Ok thanks guys ill run 12 and see how it does what's the max speed I can go on the haul road while aired down? Like 25 or what cause I don't wanna heat up my tires too much thanks, Joey
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Old 09-02-2013, 02:52 PM   #13
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25 mph at the most for short distances.
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Old 09-02-2013, 04:19 PM   #14
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Ok thanks everybody ill let you know how it goes can't wait!!!!
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Old 09-02-2013, 10:22 PM   #15
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Quote:
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16 psi is not a low air pressure for offroading at all, what width wheels are you running? A wide wheel makes it harder for an aired down tire to remain seated. Typical aired down no problem air pressures for that size tire are 11-13 psi.
That was with stock rims and 29.5x9.5 all terrain tires. Forget the model. Equivalent to stock.

I'm now running 31x10.5 Duratracs on MB TKO's 15x8 and airing down to 18 and no troubles at all.
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Old 09-02-2013, 11:49 PM   #16
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Lowest I have been is 18 on my mtr/ks but I'm running a 15x10 and I'm a little worried to go lower I'm going to try 15 next trip out cuz I now have a trailer to tow my jeep home of I need to instead of having to drive home on a spare.edit mine are 35 12.50 15s
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Old 09-02-2013, 11:52 PM   #17
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33x12.5R15 MTR's with Kevlar side walls on 15x8 PC alloys, I'll go down to about 12-13 psi
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Old 09-03-2013, 01:32 AM   #18
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Lowest I have been is 18 on my mtr/ks but I'm running a 15x10 and I'm a little worried to go lower I'm going to try 15 next trip out cuz I now have a trailer to tow my jeep home of I need to instead of having to drive home on a spare.edit mine are 35 12.50 15s
I ran my mtrks today on John Bull at 10 and had no problems. I normally run them at 10. 35x12.5x15 also
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Old 09-03-2013, 08:32 AM   #19
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I ran my mtrks today on John Bull at 10 and had no problems. I normally run them at 10. 35x12.5x15 also
What size wheel do u run
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Old 09-03-2013, 10:05 AM   #20
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That was with stock rims and 29.5x9.5 all terrain tires. Forget the model. Equivalent to stock.

I'm now running 31x10.5 Duratracs on MB TKO's 15x8 and airing down to 18 and no troubles at all.
You're not really even aired down until you get below 15 psi. You can safely take those down to 12-13 psi.
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Old 09-03-2013, 11:08 AM   #21
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What size wheel do u run
15s
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Old 09-03-2013, 12:00 PM   #22
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15s
X8 or x10
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Old 09-03-2013, 12:06 PM   #23
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x8 or x10
x8
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Old 09-03-2013, 01:10 PM   #24
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x8
Ok yea I have 10s that's what worries me about going low
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Old 09-03-2013, 01:25 PM   #25
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How about a 7" wheel with 10.5 31s?
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Old 09-04-2013, 12:43 AM   #26
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So just going to an offroad park where there's mud ( of which in trying to stay away from cause its a pita to clean and not much fun no skill in it really) rocks hills trails and sand just general everything. So for my setup you guys are recommending 12psi? And yes I do have a small air pump for my cigarette lighter to air up it may take a while but it will work. Any other suggestions? Thanks, Joey.
Cutting off the cigarette lighter plug and using alligator clips directly to the battery may save your pump from burning out.
When airing back up have the pump running first then insert into tire this too will help save the pump.

Have fun
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Old 09-30-2013, 01:20 PM   #27
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Yesterday for the first time I finally got a chance to air down my 33x12.50 MTR-K's (on 15 x 8 rims). Prior to, I haven't had any way to air back up, but just purchased an MV50 to do the job.

Aired down to 12 psi per recommendations. WOW... I never thought the difference would be so dramatic. Not only comfort, but confidence & stability were greatly increased. Even at 12 psi the MTR's didn't bulge significantly, and washboarded, rutted dirt roads were very comfortable at 35 mph.

The MV50 took 3 minutes 15 seconds per tire to go from 12 psi to 27 psi. To me that was more than adequate. I now have no plans to replace the pump with any sort of uber-expensive OBA setup in the future.
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Old 09-30-2013, 02:28 PM   #28
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^^Awesome. I did not think airing down would make such a huge difference when I bought my Jeep.
I start out at the trail head with 10psi. 15x8 wheels, 35x12.5x15 tires. Even less in deep snow. Remember, you will gain psi as you gain altitude. Something to keep in mind on your way back down if you air down a little more up top.
Here in WA, the trails mostly start in the mountain valleys and go up from there. I am guessing Wyoming might be the same?
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Old 09-30-2013, 05:27 PM   #29
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Good point about the elevation! Fortunately in this case I actually aired down at about 8000 ft & didn't go much higher... but I'll need to bear that in mind for future runs. In fact, my next "big" excursion involves starting at 6000 ft and ending at about 11,000 ft. (i'm running out of time this year tho) I hadn't considered the elevation change at all.
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Old 09-30-2013, 06:33 PM   #30
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I run my 35x12.5x15 Mtrs down to 10 psi without bead locks sometimes. On a typical rocky trail, ill run 12psi. I wouldnt worry about speed at lower tire pressures unless you plan on pitching the jeep around corners. I run on the highway between trails with 12 psi up to 65 mph.

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