Airing Down

[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

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