Tire pressure for sand on my sprinter.

[Paddy]

What pressures are we running in sand on the vans? I'm 2wd and need maximum sand capability. My gut tells me that anything over 20psi won't really help, but I fear that too low may risk a bead problem. I'm running 245/75-16 E rated AT hankooks. Not sure loaded weight but I'd guess each end at about 3000lbs in current trim maybe 3500 on rear.

Is 15psi too low? 12?

 

[broncobowsher]

The softer the sand the squishier the tire should be. At some point going bigger (wider and/or taller) becomes the better option.
So how soft of sand you you planning on going through? Wet beach sand (picture above) isn't that bad. Full highway pressure is probably going to do pretty good. Driving through stuff that is loose and powdery, difficult to even walk in... You are going to be dancing getween so low you roll a bead off and still too much that you sink in.

 

[Paddy]

Ya wet sand "normally" hard but this day in this spot it was actually quite soft. We have here on Oregon beaches a soft sugar sand that is incredibly hard to drive in. It will stuck a dirt bike easily. It will stuck a lightweight 4x4 with big tires. So it demands maximum respect and good equipment. Well sprinter not really designed for these conditions. We got away with full pressure yesterday and usually but sometimes the wet sand isn't as hard as predicted or as bountiful. This particular spot is where we need to frequently tread also, and due to the last winter storm rearrangement the low beach is about 15' lower so tide is a major issue now where it wasn't in the past.

 

[luthj]

As you air your tire down its profile becomes longer (and a little bit wider). Ideally for soft and deep sand you want the longest and narrowest contact patch possible. With a narrower patch you have less sand to push out of the way moving forward while the long profile provides flotation.

Your contact patch at 20psi will be about 3x larger than at 60psi. Any amount of air down will make a difference though. For a lightly loaded van, 20PSI should be plenty safe. If you are content to go very slowly (and be careful about unseating a bead) you can go down to 15PSI. Just remember that you cannot drive fast at these pressures. The extra tire flex will cause rapid heating of the tire which can lead to failure (sometimes months down the road).

If you are at max GVWR I would not go any lower than 20PSI on stock sized tires.

 

[Paddy]

Cool that sounds about right thanks. I'll edge down slowly from 20 and see what happens. I don't mind blowing up a tire because I got a good warranty on them

 

[mikracer]

There are guys out at the dunes here that run as low as 5-8psi. Those are regular trucks though and not as heavy as a loaded van. I bet you're safe going down to 15psi with regular driving. As far as having to go slow on the sand, I'm not sure that applies as it does to driving on asphalt.

 

[Paddy]

Ya that was my thinking too. Guys with big tyres and smaller rigs air down more for wheeling but I'm not wheeling this thing just driving where I shouldn't. And sharp turns and objects not so much a consideration so should be able to go a little lower than equivalent trail rig may want to without bead locks. I guess I'll just have to try it out and see how much flattening I get at 20 and 15. Thanks.

 

[TeleSteve]

Generally if you measure the height from ground to bottom of rim fully inflated, then air down until you have reduced that measurement by 25% will give you the largest contact patch and still be able to handle the weight. Once you have done this once you will no the pressure to run. front to back may very, and you may have to change if you are more or less loaded.

 

[luthj]

There are guys out at the dunes here that run as low as 5-8psi. Those are regular trucks though and not as heavy as a loaded van. I bet you're safe going down to 15psi with regular driving. As far as having to go slow on the sand, I'm not sure that applies as it does to driving on asphalt.

The surface doesn't affect heat build up all that much. The majority of heat production in a tire comes from the flexing of the tire itself. Less air means more flex. So you need to lower your driving speed appropriately. 40 mph on dirt will heat a tire pretty much the same as 40 mph on sealed roads.

Generally if you measure the height from ground to bottom of rim fully inflated, then air down until you have reduced that measurement by 25% will give you the largest contact patch and still be able to handle the weight. Once you have done this once you will no the pressure to run. front to back may very, and you may have to change if you are more or less loaded.

Good advice, especially for vans with large front/rear differences in weight distribution. On my fully loaded sprinter about 35 rear and 25 front seems to be the sweet spot for dirt and washboard. I would consider dropping another 5-10 psi for soft sand, but I haven't had the need to yet...

 

[Haf-E]

Many sprinters are so front heavy that they tend to plow the front tires in and you get stuck... Might be worse on the long wheelbase version I have.

 

[Petrolburner]

I have the same size tires on my Ford van and I use Trailhead Deflators to air down to 25 psi in the dirt. This seems to be a comfortable spot to mellow out the washboard, increase traction and still keep me safely on the bead. It also allows me a margin to air down farther if I get stuck in soft sand. For your case I'd suggest looking at the tire and decide how much deformation your comfortable with. Also, pay attention to when the van gets slightly crossed up in uneven terrain and applies more pressure to one wheel than the other and make sure the air pressure isn't too low at that point. That will be the worst case scenario that you'll want to be prepared for. Don't rule out the possibility of running different pressure front to rear either.

http://www.4x4review.com/trailhead-automatic-tire-deflators/