Air down or not?

[WanderingTs]

My most rugged off roading is done in an area of granite lava flows. This makes for a lot of slick rock, large rocks, ledges, and "potholes" in solid granite. Most if not all of these obstacles are height driven, so the more clearance, the better.

My original 4X4 was a Chevy S-10. The only lift I had on it was larger tires. My uneducated logic was, why would I air down? Airing down could make me lose a small amount of height, plus make me sink even more coming off an obstacle as the tire compressed. Now that I have my Commander, I am surrounded by those who air down for 4 wheeling.

So my questions to the forum are: Do you air down, if so how much, and what (besides ride comfort) are the ups and downs?

[LWM]

I air down on most trails/roads that are not smooth, my purpose is to make the ride a smooth as possible. I do not drive in sand or mud (there is none near where I live) so that is not a concern and I feel my current tires and the power of the Hemi will move me through or over almost anything. But on the longer rides it is nice to have a smooth ride and reduce the jaring as much as possible and for that reason I will air down to about 25Lbs of presure.

[HueyPilotVN]

Another reason for airing down is that your tires will deform and get better traction on large rocks and especially on granite slick rock out west if they have lower air pressure. I have seen some actually wrap themselves around the curve of a rock. Too low of air pressure can however cause them to come off the wheel rim. I have gone down to as low as 15 psi when I used to do more hardcore rock crawling with my last TJ on trails like the Rubicon, Dusey Ershem, or Kaiser pass in California. As Jon mentioned the best ride comes from lower air pressure where the tire is not rebounding from the rocks or trail.
Many of us carry air compressors mostly for airing up. We actually had a give away of free air compressors on the first Sedona Trail run.

[Sal-XK]

Well I have been rock crawling both ways. Not airing down is diffidently a bouncy ride. It also makes obstacles harder to get over approaching a rock fully inflated your tires first action is to bounce off the rock. The same rock aired down like Huey said the tire will actually conform to the rock and you just crawl right over. I to was concerned about ground clearance and was the reason why I did not want to air down but really how much can we be loosing. All the guys I went with aired down to 16PSI and they had no issues. I have never had to air down at the beach yet even though I see people stuck all the time including my bro's wrangler following me but If I ever do get stuck on the sand I would air down 20PSI and drive away. So for sand mud feel it out I guess but rocks and stuff I would air down.

[El Cid]

I confess that I personally don't air down as far or as often with my XK as I did with my old LJ.

In the majority of Jeeping conditions the air-down advantage is predominantly about ride (like the above posters noted). My ride is already so much more cushy in the Commander that not airing down results in the same bouncing I got after lowering the LJ. So a lot of times I just don't bother, even though I carry a portable compressor in the rig for quick airing up.

On the other hand, there are Jeeping conditions that simply demand air-down. The clearance loss is minimal, and you get much better traction over rocks as the tire flattens out (and you lose the "bounce-off" and such, too). In those cases, I go down to 20 or so with my 285s. Nicely squishy with little chance of popping the rim.

[NeilSmith]

I aired down on the beach to 25 lbs. I didnt try it without airing down and I did see a bunch of people stuck. i had no problems at all.

[WanderingTs]

Has anyone noticed a difference in tire wear? How about the chances of getting chunks taken out by a sharp spot? Logic seems to tell me that a squishy tire's tread would be less likely to be rigidly pushed into a sharp spot, but more likely to try to "hold" onto a sharp edge of a ledge instead of cleanly rolling off.

Airing down seems like it would make for more exposure to the sidewalls by rolling them outward and closer to the ground?

Airing down for Black Bear Pass in Colorado I ended up with a few chunks missing from my tread. The Chute area was similar to what I do here in CA, and I normally do not lose chunks from my tire treads. These are new tires though, so I don't know if it is the tires or the airing down that is more at fault.

[07JeepXK]

I air down everytime I go off roading. Usually I air down to about 16-18 psi.

[Sal-XK]

well if you have Mt's or AT's something other then street tires they are actually made to be aired down. Thats were the importance of how many ply's your tire's have and such. Maybe discount tires can chime in on the subject.

[Doc in AZ]

terrain, tire and rim selection will dictate the tire pressure you will run.

i am a rock crawler & i run 35 / 12.50 / 15's on a rim that is 8" wide. i typically air down to about 9psi. my buddy that runs bead lock keeps his about 3-5psi. when i had rims that were 10" wide i was having problems with "burping" air from the bead at 12 psi. IMHO a fully inflated tire is more prone to being punctured as it is not going to flex. thing of a fully inflated balloon and how easily they pop, but with it half inflated it is more yielding. for research purposes, go out to your jeep and measure the bumper height front and rear. air it down and measure again. it will be a nominal difference. a tall sidewall like i have (10") will have more flex and will have a larger difference from fully inflated to aired down. but with a larger rim size like 17" and a 32" tire (about 7") will have much less difference.