Air Down Pressure for riding on sand ?

[BajaSportsmobile]

Originally Posted by BIGVANS

WOW! What brand tires?

When I got stuck it was the Factory delivered 18" Continental Tires, don't remember the exact size and model. They came stock on my 2005 SuperDuty. I have since been through two other sets of BFG 315/70R17/D (Oh my - D rated) in 80K miles. The truck is really only used for towing and supporting my Desert Racing efforts. It carries 115 gals of Diesel in the bed tank and 47 gals under the bed in the Transfer Flow tank. It is usually also loaded with 2 to 3 55 gal drums of race fuel and other parts and is towing a 24 foot enclosed trailer with the race truck, spare tires and parts in it. I also haul a 5 ton dump trailer with it that I have had 13,000 lbs of concrete in. On the scales it has been over 23,000 lbs between the two. I have never had a flat tire with it, let alone a blow out.

I put the exact same BFGs on my SMB, EB, V10, Penthouse... don't know the weight though it will never weigh as much as my truck has.

On trips to Baja with the Truck, I air down to 25 once I hit the dirt and usually don't air back up until I get home. One trip I towed my Seadoo GTX all through Baja exploring for several weeks, had the Lear Shell on the truck and loaded - 25 Psi and the Jetski trailer with 31 inch tires aired at 8 Psi. Left San Felipe the day after the Baja 1000 race went through and took the the course to Gonzoga Bay (that road was really chewed up) and then out through Coco's and down to Bay of LA, San Francisquito, Conception Bay... 25 and 8 Psi.

[capnjim]

CarringB,

It looks like your rig is a dually, are you airing it down to ten psi? Don't the tires rub? I've been afraid to have the tires touch. I'm running 235 85 16's BFG AT's on my dually and didn't want to hurt the tires.

Jim

[carringb]

Originally Posted by capnjim

CarringB,

It looks like your rig is a dually, are you airing it down to ten psi? Don't the tires rub? I've been afraid to have the tires touch. I'm running 235 85 16's BFG AT's on my dually and didn't want to hurt the tires.

Jim

Generally dually tires should not touch, but that's because of heat build-up at highway speeds. With the off-set of the Goliath wheels, they still don't touch even at 8 psi. But if they did, I wouldn't worry about it at all.

[Ford_6L_E350]

I wouldn't worry about dually's touching. They are both going the same direction and speed, so no rubbing, no heat buildup, no worries.

Mike

[Carl]

Great idea to "test" various pressures and really see/feel the difference. I normally run sand with most vehicles around 20 psi, the Sportsmobile at 30 psi, and can go most anywhere I want with ease. That said, I stuck my Tacoma in deep snow one day, all alone, spent time digging out at 20 psi, then lowered pressure down to around 5 psi and drove out with no problem. Bruce at Overland Experts has done some great research on ground pressure and tire footprint, also some good stuff by Scott Brady (expedition portal).

Best to test these ideas in conditions where you can fix a tire if needed, and certainly at low pressure try to stay straight as quick turns may hurt you.

[geoffff]

Those of you daring to go down to 10 PSI with your Sportsmobile -- you win! My tires look almost flat at 20 PSI, and I get little hairline cracks in the tires near the bead -- so I don't dare go lower.

My RB50 is on the lighter side (9500 lbs). I run 55 PSI highway, 30-35 PSI off-highway, and 20 PSI in soft sand. I just got back from Baja (more stories to come) where I got into deep sand at 30 PSI. Even at 30 PSI, the van started digging in, so I dropped to 20 PSI, and was good to go. I never exceed 30 MPH at this tire pressure.

-- Geoff

[quigley513]

In my experience, tires de bead when presenting a side wall in the direction of the force. I have seen off road rigs with fully inflated tires de bead where the driver has cut the wheels sharply while plowing mud down a hill. And, conversely, drivers who approach hills at right angles can operate with very low pressure. There is a point, however, when sidewall distortion becomes a factor in debeading.

[ridintall]

I popped a bead on a rear tire on the beach after airing down a little too far, although I was towing my off road trailer too loaded down with gear and deer. It destroyed the tire and was a good reason to go up to an E rated tire. I've always replaced tires in pairs and then done the other pair shortly there after. I'm on my third set of BFG's and have 89K miles on my van. I think 25-30 psi is fine for beach travel in a 4x4 SMB, although I rarely check pressure when I air down. I can tell pretty well just by looking at the tire after all these years. But now I'm curious and since I'll be going to the beach soon, I'll actually check when they look "fat" enough.

[quigley513]

I have two rigs with Staun internal beadlocks but not on the van. I can say that it gives me a lot of confidence when I drop the tire pressure way way down. I have 35" BFG Krawlers on my Jeep Cherokee and I take those all the way to zero psi and the beadlock pressure is 50psi so even with the sidewall deformation they don't even begin to separate from the wheel. I question whether a Staun beadlock tire and rim can be truly well balanced, though. It can certainly look balanced on a spin machine, as mine have done, but with all the junk inside the tire, I question that for a passenger rig like an on-road van.

Nonetheless, if one is going across the Altar Desert or other trek on soft sand one might consider them.

[ridintall]

Took a trip to the beach this weekend, pulled over to air down and couldn't find my Sun Performance tire deflators; bummer bro...had to do one at a time and it took forever. It was 3am and we were tired so I didn't check the pressure but it was clear I needed to take more out once we got on the beach. Took more out the next day and it made a huge difference. 26psi is what the gauge said once we were back on pavement and I could verify they looked nice and fat like I usually set them at.

I'm buying a couple more deflators this week to replace the one I've had since 1995.