Airing Down

[Grouseman]

This may or may not be the proper place for this question, but here goes. Were going to be driving on the beaches of the Outer Banks, what tire pressure should be used? Someone mentioned 20 psi before, is that about right?

Gman

[Jonathan Hanson]

Gman, you should be able to go lower than that in sand with no problems. I'd try 18 at least, or 16. Some people go lower, but personally I've never felt the necessity. The danger with going too low, of course, is having the tire bead lose its seat in a high-torque situation, which instantly evacuates any remaining pressure. But if you stay at 15 or higher the chances of that are remote. I saw it happen once and that was someone running under ten psi on non-beadlock wheels.

[awalter]

I consistantly run 10-12 PSI on my Tacoma ecab in soft sand. If I have a fairly heavy load, I don't go below 12-15 PSI. If you drive recklessly, spin donuts etc you will pop the bead. In over 25 years of soft sand driving, I have never popped a bead.

[goodtimes]

10 psi is what I use for technical (rock crawling) trails. If it is just sand, 7 - 8 psi....as Al mentioned, driving slow and deliberately is important at those pressures w/o bead locks.

Alot of it has to do with the tires and vehicle weight though. For example, with a D rated tire on a 3700 pound jeep, I run much lower pressure than I do with the same tire and a 6600 pound truck...or a C rated tire and a 4800 pound truck.....

[Grouseman]

Sorry guys,

I have an 80 series Landcruiser. It weighs approx. 5800 pounds and will be loaded somewhat, but I will be pulling my little M101CDN behind the Cruiser. The 101 (1/4 ton) weighs in at 750 +/- pounds, and I will have about 300 pounds of cargo added to that.

Gman

[BajaTaco]

Yes, I think the size of tire, type of tire, and the weight of the vehicle are all factors. Larger tires can usually afford to run lower pressures than smaller tires. For your 80 series, if you are using a 32" or 33" tires, I would say that you could go down to 10-12 psi without an issue. BUT, what I would do is try running a little higher psi first (say, 15-17 psi), and if you find yourself bogging too much, then let some more air out. If it is a scenario where you can't even risk a bog and loss of momentum (i.e. crossing a flat at low tide) then I would go down to 12 psi, or even 10 psi if you want to take a little more chance on the bead in trade for a little more traction insurance. The reason I say to try a little higher pressure first is more for the sake of convenience. Typically if I am driving in the sand on a trip, it's only for a small segment or portion of my total trail time. I don't want to run regular dirt tracks with super low sand pressures, so if I can get by with a compromise pressure then I don't have to mess with airing up and down every time I enter and exit the sand. (Don't use this compromise pressure though if there is risk of getting stuck below the tide line, or if your engine or trans. will overheat easily).

For the trailer, I can't offer an opinion based on personal experience. My guess is that since the trailer is very light and likely on the same size tires as your 80, that you can go to the very low end of the pressure range - 10-12 psi or even lower (8 psi) with no issues. The trailer likely won't be heavy enough to damage the bead, and won't have power to the axles that could "spin" the tires on the bead.

Do a little test in your driveway right before you leave for your trip, so the vehicle has the full trip load on it. Meaure the distance from the ground to the bottom of your wheel rim at full street pressure. Then let air out until you have reduced this height measurement to 75% of what it is at street pressure. Let us know what you come up with. This will likely be the sand pressure you want to go with.

[VikingVince]

Isn't there also an issue of the size of your tire footprint at low PSI? Meaning...if you get no larger footprint at 8 psi (or whatever number)than you do at 12 psi, then there's no point whatsoever in going to 8 psi...this is possible depending on tire size and weight load on different vehicles

How to measure footprint: In your driveway or on concrete air down to 20, 15, 12, 10, 8, etc. At each psi, measure the footprint by sliding a piece of paper in front of the tire and behind the tire until it stops. Then measure the distance between the two pieces of paper. As you air down the distance increases/footprint gets larger and longer (more traction)...but at some point the footprint will not change...thus no point in going below your biggest footprint.

[Grouseman]

Well this thread is getting interesting. By the way I have 285 Revos. Don't you guys think airing down to say 25 psi and trying that first, then if needed go down some more. More air in the tires less chance of losing the bead.

Gman

[Scenic WonderRunner]

I'm new to this airing down idea (I know folks do it...it's just new for me to do it). I will just share my experience......then I need to go back up and read this thread in more detail. Remember, I'm just sharing my experience and NOT picking on Anyone's thoughts or ideas here! Just sharing how I feel.

For almost two years I have never aired down. Two reasons. I normally travel alone.....and I didn't have an air compressor. I now have a little MV50....so I solved that problem. The alone thing is still hard to overcome....but that's why I'm here!:ylsmoke:

Back in Feb. '06 I went on a trip up Goler Wash in the El Paso Mtns. Somebody behind me thought I needed to air down.....although I was making it just fine.....my truck is really light!

I agreed to air down to 24psi....but no lower (I have nice Factory Toyota Upgrade Original Alloys $1,200 upgrade in 1988!!$%).

At the end of the day.....I had lots of sidewall tire rubs....and three nicks on my drivers side rear wheel. For two years....I have Never even put a nick on my truck!

So for me.......the pain I suffered from feeling stupid for airing down and getting the rubs and nicks.....was not worth the airing down just because everyone else was, and because somebody "thought" I needed to. Especially since I was making it fine up the wash in the first place.

I would prefer to air down if and when I feel like I'm going to have trouble moving ahead. Although I can understand the benifit of airing down while running on a very long washboard track.....or trying to tackle a steep rocky slope where you need a wider footprint for more traction.....or in deep sand.

I think airing down has it's place.....but for me....it's not 100% of the time.

OK.....I think I'm done for now.....

(ducking for cover!)...............:elkgrin:

[justfred]

My Dad taught me to always air down when off-roading. In sand we went as low as 8-10 on BFG ATs and never de-beaded (I never even knew what that was until recently).

One of the other reasons to air down for better traction, is so you have less impact on the terrain. Less wheelspin, shallower footprints, less rock displacement. Sure, you can "power through" or you can crawl through and not leave a bunch of scars. On sand, a properly aired down tire can have less psi on the ground than a person walking (though a much wider footprint). Often I've had this be the difference between breaking the surface, and floating over the top.

[Jonathan Hanson]

Justfred, thanks for pointing out the trail impact aspect of airing down. Most people think it's just done for traction and flotation, but it really does reduce degradation of the substrate. The corollary to this is shifting the truck into four wheel drive at the earliest possible time - something seen as vaguely sissified by too many macho drivers.

[jim65wagon]

I always start my OBX tours at 20 psi, if I feel I need less than I'll go lower. The reason for starting at 20 is that there is always at least one trip to town, which winds up with a short and slow drive, (about a mile) on pavement. At 20 the Tun feels stable enough to safely negotiate the few curves. BTW its great with the air compressor, pull off the beach, hit the roadside, air up, drive off. Back to the beach, stauns do their job and you're off again.

[datrupr]

Mark, nobody's going to blast ya for not airing down. I don't always do it, and I am sure a lot of people here do not air down all the time. For me, I will air down on washboard roads for more comfort, and then when I hit the two tracks, sand, or rocky gravelly stuff I am already aired down so no issue there. I am also with Jonathan at I will usually engage 4WD as soon as I hit the dirt tracks for the sole purpose of a little more control on the corrugated roads at a slightly higher speed. I usually never air down below 20psi though. Even in the sand at the Bill Williams River a couple of weeks ago 20 psi seemed to work fine. I could have gone lower but I was not having any problems with the pressure I was running. Except for the that first steep hill.

[offroad_nomad]

I usually run at 15-18 psi when we're on the beach with no problems.

[awalter]

Many good points made about airing down. You have to feel comfortable with what your doing. To folks that are somewhat new to the practice, it may make more sense to air down in stages versus all at once. Definitely tire size, construction, load & terrain are directly related to what pressure you should be at, at any given time. If your only doing a short stretch of sand, I wouldn't air down until needed.

But, when I hit the beach next month at El Golfo for for 5 days of camping with 50 miles of beach to explore, the first thing I do is lower the pressure to 10-12 lbs both on my Tacoma & my 16' Airstream. When on a dirt trip for a few days, 20-22 lbs until back on pavement usually a day or two later.

When doing dirt & pavement, dirt & pavement, I will rarely air down unless specifically needed for traction.

Again, you have to be comfortable with what you're doing. Know & trust your equipment. Have the appropriate on board equipment for the terrain your exploring. Decide what works for you & your vehicle by experimenting. And by all means respect the environment.

[BajaTaco]

Isn't there also an issue of the size of your tire footprint at low PSI? Meaning...if you get no larger footprint at 8 psi (or whatever number)than you do at 12 psi, then there's no point whatsoever in going to 8 psi...this is possible depending on tire size and weight load on different vehicles

How to measure footprint: In your driveway or on concrete air down to 20, 15, 12, 10, 8, etc. At each psi, measure the footprint by sliding a piece of paper in front of the tire and behind the tire until it stops. Then measure the distance between the two pieces of paper. As you air down the distance increases/footprint gets larger and longer (more traction)...but at some point the footprint will not change...thus no point in going below your biggest footprint.

This is an excellent point to bring up Vince, and as you said - it depends on the vehicle and tire combo. Basically, a lighter vehicle with a stiffer sidewall is more likely to encounter the scenario you describe. But a vehicle like my Tacoma for instance (5,100-5,400 lbs on 32" C-rated tires) does not experience that "point of diminishing return". My footprint keeps increasing for every pound of air I let out - all the way to flat.



I think airing down has it's place.....but for me....it's not 100% of the time.

Yea, for me it's not 100% of the time either. And I must admit that this is often a result of "convenience" or sometimes good old fashioned "laziness" on my part. The truth is that in a technical sense, airing down a tire does in fact increase vehicle traction and reduce wear on the trail. Sometimes, I perceive that increase to be nominal enough that I won't bother airing down just because it will save me from airing back up. Or I will air down, but not very much, so that I don't have to put so much air back into the tires when I reach pavement. This is usually for short trips that will be maybe only an hour or two in duration, and where the use of 4wd is almost not required (i.e. very mild trails). A good example would be the recent Secret Pass trip. I didn't bother to air down for the dirt because I just didn't feel that the terrain warranted it, and I knew the time on the trail would be fairly brief. Had we been on the same type of trails, but maybe for a duration that was twice what it was, I would have aired down. Call me a slacker :p

BTW, SWR, I doubt the wear marks and nicks on your sidewalls and wheels were due to being aired down. It was likely that it was due to trail conditions and purely a coincidence. In fact, since you are running stock width wheels, airing down will actually do more to protect your rims because of the resulting bulge in the sidewalls.

[flyingwil]

Well this thread is getting interesting. By the way I have 285 Revos. Don't you guys think airing down to say 25 psi and trying that first, then if needed go down some more. More air in the tires less chance of losing the bead.

Gman
25 psi sounds high, I would go down to about 20 for a starting point. You can look at your tread pattern in the sand and see if you need to go down more, where the sand is wet. It seems that you are worried about your beads, so just dont go below 13 psi and you should be fine. If necessary (stuck), lower the psi to 10. The softer the sand, the lower the pressure that is needed. This will give your tires a bigger area that will allow your tire to float over the sand, rather than dig down into it. The more tire rubber you have on the sand, the more support your tires will have if one of them gets stuck. You must deflate all four tires, because the front two create sand hills that the rear must climb continually.

[BajaTaco]

FWIW, I don't think the busted bead issue is too much to worry about in sand, unless you are doing some really fast and hard playing with lateral forces on the tires. In sand, there isn't much to hold onto the tire that would create a condition where the tire has so much contact pressure that the wheel wants to turn inside of it (like you can have happen on rocks).

[david despain]

http://www.expeditionswest.com/research/white_papers/tire_selection_rev1.html#performance here is a fantastic article written by a fellow some folks around here even know by name. its got the "skinny" on tire selection and airing down. i think every one ought to read it at least once

[OldSven]

I stick to around 15-18 in the rocks (some street driving is necessary sometimes), but when at the dunes I think I run around 8-10. The deeper the sand the lower the pressure:sport_box