Tire pressure question for beach runners

[Ripit]

I drive a Chevy 2500HD Dura with a Outfitter Apex with stock wheels and tires. I'm about to start hitting the beach to do some surf and kayak offshore fishing. I'll be in the Padre Island National Seashore (PINS) area. The sand on this beach is med to soft. For those who know the area I will be past the 5 mile, 4 wheel drive only sign. Probably somewhere between the 15 and 40 mile markers. Just curious as to what poundage you would air your tires down to comfortably not to roll one off the rim. I carry a portable air compressor to air back up, but don't want to have to remount a tire back on to the rim. I have done a lot of jeeping in the past with bead locks where we aired down to 5-8 lbs but I know that's a bit low without beadlocks and this much weight. I'm thinking 20-30 lbs but thought I would check with some of you who have done this with there popup camper. Thanks

 

[bob91yj]

I'm in the same boat you are. I'm used to driving Jeeps, I know what I can and can't do with them.

I ran 25 psi in my truck tires (BFG A/T 315/75/16) last weekend with no issues, could probably have dropped down to 20 psi if I'd needed to. I ran 60 miles or so round trip on dirt roads with some soft sand. I've got a slide in camper in the truck along with some other stuff, maybe 1200-1300 pounds in the bed, plus two adults and two 80 pound dogs in the cab.

 

[JHa6av8r]

Been wondering about this myself. I'm about 9,500# loaded. I was thinking 40# is as low as I'd go unless I need lower but interested to see what others think and do.

 

[bob91yj]

I've run mine on the pavement for 30 miles or so at 30PSI while connecting the dots on a Death Valley trip.

 

[1stDeuce]

It's not quite the same sand or loading, but I've run 13 in a mostly empty GMC 2500 out at Silver Lake Sand Dunes in Michigan with no issues, and I flogged it pretty hardgood. With as much weight as you're carrying, I'd say start at 30. If the sand gets really soft and you're adding a lot of throttle to keep moving, drop a little more out until the truck isn't working so hard. If you drop into a soft spot, and it starts to spin, STOP and let some more air out. It's amazing what dropping pressure will do for mobility, and you can always air back up some when you're on firmer sand.

You're not going to roll a tire off the rim unless you're doing hard turns at speed, even at fairly low pressures. I ran my old full size chevy on 33's at 8psi, and my jeep on 285's at 5psi and never had a problem. Don't do donuts, or sudden really hard turns and you have nothing to worry about. For emergency situations, air down as low as you need to. With as much weight as you're carrying, 15 psi is probably about the useful lower limit, but you'd be surprised what it'll get you out of!!

Post some pics when you come back!!!

 

[bajajoaquin]

Once I go off road, fully loaded, I air down to 25psi front, 30 psi rear. That got me across a four-mile stretch of beach, which was admittedly pretty firm. Once I got to a soft hill, I got stuck. From there, I aired down to about 15psi and drove out.

I'd go down to 25. With Load Range E tires, you're not going to see a whole lot of sidewall bulge before you get down to 35psi. If you get stuck, air down more until you get out of it. The post above is spot-on. If you're not turning at speed, you can go pretty low before you roll off rims.

(I remember going down to essentially zero in my old F150 when I got stuck on the beach one time. I had like 8-ply commercial rib tires on it, and they just wouldn't flex with any significant pressure in them. I got unstuck, made a u-turn on the beach without losing the bead, and then aired back up 10 lb or so for the rest of the week.)

 

[bajajoaquin]

Just remembered that I had some vids on YouTube. This is the beach I was able to go down at 25psi:


And this is the soft sand hill I got stuck in on the way up (this is the way down). I needed to air down from 25psi to get out of this.

 

[mtnbike28]

Question? If you are running E Load tires, does that reduce the aired down bulge you get with C or D tires? I have 235/85r16 Load E tires and thinking of using some old 31" BFG AT's to get a larger footprint.

 

[Regcabguy]

Just remembered that I had some vids on YouTube. This is the beach I was able to go down at 25psi:


And this is the soft sand hill I got stuck in on the way up (this is the way down). I needed to air down from 25psi to get out of this.

My friend was out there a year ago and a full size Dodge had D-rated 355's on his rig. Flotation+. Beautiful out there. I used to drive my Landcruiser to the pt. I'd air down the 10-15's to 18#. We'd be sitting around the fire watching cars go by on the highway to the east.
One time an El Camino pulled up! It had been converted to 4x4. That trip some locals were harvesting Sargasso(seaweed) and asked us if we'd trade canned vegetables for deliciously prepared abalone and fresh tortillas. We agreed and laid some much appreciated coin on them. Good people.

 

[bajajoaquin]

Question? If you are running E Load tires, does that reduce the aired down bulge you get with C or D tires? I have 235/85r16 Load E tires and thinking of using some old 31" BFG AT's to get a larger footprint.

I'm not quite sure what you're asking. But E range tires have stiffer sidewalls than C or D. So for a given pressure, they will bulge less. There's a lot of discussion here about whether a larger D with the same rating as a smaller E is still safe on heavily-loaded trucks, and you can make up your own mind on that. But either way, I'd at least make sure that the rated capacity on the sidewall is sufficient. And I'd also worry if by "old" you mean really old, or you're just saying that as a shorthand for tires that used to be on your truck but weren't made that long ago.

 

[bajajoaquin]

My friend was out there a year ago and a full size Dodge had D-rated 355's on his rig. Flotation+. Beautiful out there. I used to drive my Landcruiser to the pt. I'd air down the 10-15's to 18#. We'd be sitting around the fire watching cars go by on the highway to the east.
One time an El Camino pulled up! It had been converted to 4x4. That trip some locals were harvesting Sargasso(seaweed) and asked us if we'd trade canned vegetables for deliciously prepared abalone and fresh tortillas. We agreed and laid some much appreciated coin on them. Good people.

Not surprised 355s had lots of flotation! I'm still regretting not upgrading a size to 285s when I replaced my tires. I still run the stock 265/75 size that came on the truck. But I'm a cheap bastard, so I'm not likely to swap out tires for another 30,000 miles, when these tires are done!

And yeah, there's good people down there. I think it was Walt Wheelock that said, "bad roads bring good people. Good roads bring all types of people."

 

[1stDeuce]

Question? If you are running E Load tires, does that reduce the aired down bulge you get with C or D tires? I have 235/85r16 Load E tires and thinking of using some old 31" BFG AT's to get a larger footprint.

Comparing E 235/85's to C 31x10.50's (I've never seen a D 31x10.50) is like comparing apples to oranges, and it has less to do with the load range than the size. If you have lots of HP, then a wider tire can work to your advantage. If you don't, then the skinny tire is better. It has to do with the skinny tire pushing less sand out of the way. I got LOTS of flex, and lots of flotation out of the old 215/85's I used to run on my 4-cyl XJ, and it did great in the sand. IMO, not worth switching tires. Effort much better spent airing down to a slightly lower pressure, and then back up a little if you need to.

 

[Mundo4x4Casa]

Ripit,
My rig is not a pop-up, but is about the same weight as my bro's Outfitter on a long bed. I've been in a lot of sand. First, there is sand and sand. This can change even on the same beach or dune. So, I have to 'feel' the circumstances as they come. I'm a long time jeeper and have deflated tires for sand for decades. A truck camper is just a lot heavier with more ground pressure per the psi in the tires. My average sandy road and tight sand running pressure is:
front on 305x65R16's is 30 psi. There is a bit but not too much sidewall flex.
rear on 375x55R16's on 12" wide rims (so called super singles) is 28 pounds. Here is a pic with this pressure: We drove the Mojave Road, 146 miles with this pressure:

On very soft blow sand or dunes, I take it down to the lowest threshold (without beadlocks) I think my set up will take:
front: 22 pounds
rear: 18 pounds. These wide high floatation E rated, 3750 # load rated tires can go lower than the little 305's on 7" rims can.
Yes I did this when I got tangled up with some sand in the Owens Valley, and pulling a trailer too.

after lowering the pressure as above:

This is the sidewall deflection at the 18/22 pound threshold. You wouldn't want to drive to New York this way:

Depending on your sand, your tires, your rims, your GVW/per axle loading, your self extraction ability, this is the basic high and low range of lowered pressure for my rig, which is similar in weight to your rig.
Jeanie and I are planning a 16 week, around the U.S. in a truck camper, clockwise, Sept. 1st to New Years Day trip, touching all the boundary states and attempting to camp on every beach that will allow it, including So. Padre. I have compressors and a 25 pound CO2 tank to get the tires back up, over and over again. If we lose a bead, a 1K pound ratchet strap or ignited WD40 will get us back on the rim. BTDT. I will post a T.R. when all is said and done.
One other thing to consider is HumVee (MilSpec) wheels. They start out with 8 on 6.5" holes and will fit on a full size pick up. You can build up the wheels to include MilSpec bead locks. The only thing stopping me is if they will fit having a 7" back spacing. I think my stock Dodge wheel has a 6.75" back spacing. When i dump my unit bearings and get free wheeling hubs and upgrade front axle parts I may use a 1/4" spacer so the brakes will clear the B. Spacing. The only good part is they are cheap and can come with Hummer tires that have 80% tread left (if you discount the bullet holes!) and are 34" tall. We'll see.
Good luck on your trip. It sounds like something we want to do and will be doing.
regards, as always, jefe

 

[Ripit]

Thanks for all the info. Can’t believe I’m answering this 5 years later. I didn’t think I had been away that long. Glad to be back.

 

[Pacific Northwest yetti]

And this thread now LIVES! haha, following though. Lots of good advice I plan on learning from here.