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Discussion Starter · #1 ·
regarding my upcoming trip in wet, soft, sand pit sand with occassional spots of deep (1-2') wet half melted snow. considering airing down the tires. any use? what PSI? i have on board air, so i can reinflate for harder trail, but i'm sure the sand will just bog us down if the tores are kept the same. input?

30x9.50 BF AT's
 

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The only disadvantage to airing down is you loose the little bit of height from the tire not being at full pressure.

On the other hand I usually run 10-15 pounds just to make the trails feel better, not quite as harsh. There are people that run as little as 3 and 4 pounds, but my minimum is about 10.

Airing down allows your tires to conform much better to the terrain than a fully aired up tire.

Joe
 

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Definitely air down in the sand. By dropping the PSI to 20, you can basically double the footprint that the tires have. Some say a 250% increase, but that's based on the fact that full pressure tires on asphalt is limited by the fact that the asphalt won't conform to the tire.

I wouldn't go below 15psi. Also be sure to have a method of airing back up. In Nantucket they require you to air down before driving on the beach, and they have an air-up station at the road.

I air-down offroad for two reasons: First to make the ride less harsh. Second aired down tires are much much less likely to be punctured on the trail. Running full street pressure doesn't let the tire conform to a rock or a root and can end up putting over 1000lbs of pressure on a very small contact point, even in normal off-highway driving. When aired down that load is spread over the root, and the dirt next to the root.

-Tad
 

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The ironic thing about this is the recommended tire pressure from Isuzu - 26 psi front and rear (at least for the 2002 Sport). But IMHO, I think that was done to deal with the crappy shocks they installed in the first place...

-- Shon
 

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i air down as soon as i hit the logging roads on the wqay to the trails. usually down to about 6-8psi for me. i wouldn't even think about not airing down. have you ever runa really rocky/rooty trail with full psi?

just curious why you had sucha bizarre question when you drive a rig with OBA?
 

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Basically the benefit of airing down is increased foot print. All the other things like improved ride and less puntures are a bonus. The bigger the footprint the more traction, generally. Basically your ground pressure is the same as your tyre pressure. As with all things there is a trade off. Lower tyre pressure means less ground clearance. If you are running tubeless anything less than about 20psi will start to jam stuff between the bead and the rim (or even push them off the rim), although on clean sand this shouldn't be a problem. I ended up having to clean beads three times one weekend after running pine forest tracks at 20psi, great traction though. Depending on how stiff the side walls are depends on how low you have to go to get a good footprint. Some of my mates run Simex extreme trekkers and they have to go down to under 15psi to get appreciable sidewall bulge (and regularly run at 4-6psi with beadlocks), where I, with Mongrels from Motorway Tyres (these are simex copy retreads with tubes in) only have to go down to 20psi to get the same bulge and hence same footprint. If you air down so you have a lot of tyrewall bulge you run the risk of putting something through the sidewall. This usually stuffs the tyre, were as something through the tread can sometimes be repaired.

It is interesting to note the recommended pressure for a 2002 Rodeo is 26psi. That is only a few psi more than I used to run my tubeless Cooper STs at off road on my first gen Wizard (Rodeo). These are now my road tyres that I run at 38psi. If the stock shocks are crappy put some OMEs in. Finally on sand less tread is better, ie an AT is better than a MT which is better than a Simex type tyre, as they tend to dig in less.
 

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Discussion Starter · #7 ·
TrooperJay said:
just curious why you had sucha bizarre question when you drive a rig with OBA?
What is OBA? maybe i can answer...
 

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OBA = on board air

This is normally either a compressor or CO2. The "Truck Air" brand compressors are generally considered the best of the cheap 12V compressors. At the other end of the spectrum as far as compressors is concerned are AC compressors converted to air. These can outrun any home compressor that you can buy at the home center or sears by a factor of 2 or more.

-Tad
 

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I would also recommend the Bushranger compessors. These are clip on the battery type. Takes about a minute and a quarter to inflate a 255/70/16 from 20psi to 38psi, compared to 5min+ per tyre for a "home hanyman" compressor. I've now got mine permanently mounted with a tank and pressure switch. As I understand it Bushranger has been bought out by ARB so your local ARB dealer should have some. If you want big volumes of air you need to go engine driven, either use your AC compressor or install a second on or one of the other engine driven compressors out there.
 

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Discussion Starter · #10 ·
oh OBA - on board air. these internet abbreviations are a little far fetched at times...

a few years a go my car had a slow leak from the valve stem, and i go on long canoe trips so coming off trip to find a flat was common (fix the tire? why be so silly)
so when i bought the rodeo, it just seemed natural to throw it in the back compartment. i guess that isn't really 'on board air' like in an ARB context, but i can still inflate a tire in the woods...

now that i have officially caught the off road bug, it seems like a useful piece of gear rather than just an emergency thing...

airing down it is!
 
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