What tire pressure on the low end with a full-sized truck?

[zonker]

I am getting ready to head out to the Mojave and of course that means there will be sand. I am curious as to what kind of low pressure I can use with my Dodge 2500 and easily keep the bead seated? Here is the scoop on my setup. It is an '06 with a Cummins and FWC Hawk I have upgraded tires to one size larger.. 285/70/17s in a Goodyear Duratrac in a load range D.. which will handle 3195 lbs per tire at max pressure. Generally I have 52 lbs of pressure in each tire for general use. Also I have the standard Ram LSD in back.. nothing in the front. Stock suspension that is mildly compressed due to the completely loaded weight just shy of 9,000 lbs which is very well distributed and close to 50/50 front to rear.

So any thoughts on what my lower limit on pressure would be? Also what would be a good all around pressure for general off-road? This is a new setup for us.. and especially sand.. so I would like to cheat on the pressure as much as I can and avoid taking out the Maxtrax too often!

 

[bob91yj]

I've taken my Dmax down to 30 psi, was solid enough there that I think 25psi would have been no problem. BFG AT's 315/75/16, Load range D.

 

[Jr_Explorer]

I swear I was going to post the same question this last weekend! I too have a 3/4 ton diesel (6,900 lbs. empty) and was wondering the exact same thing. I would love to hear some additional opinions.

 

[Larry]

Tire pressure is just one of those things you have to play with to see what works best for your specific rig and the specific tires you are running. My truck is a bit lighter than both of yours (8,000 lbs when fully loaded) but it seems to do well at 15 front – 18 psi rear. Got new tires (different brand) coming so I’ll probably be playing with tire pressures again to see what it will like on the next set. I would think for a heavy diesel truck 20 to 25 psi would be about right.

I also run Q78x16 Superswampers for local trips to the mountains where I usually let these down to 10-12 psi. Swampers are weird, all four tires are at 12 psi in this picture but the rears look flat and the front look full. These really deflect with weight bias whereas the cheap Kumho’s don’t as much. Sure rides nice and grips like crazy though. I am trying a set of the Fierce Attitude load range E tires next.

 

[crismateski]

as stated, you just have to play with it, but i have an 06 Power Wagon with 305/70/17 Nitto Terragrapplers. I have had them down to 10, and the bead held. In actual use, I usually run them between 18-23 and have never had a problem

 

[ExpoMike]

Our rig, ('97 Ram, FWC 8,800 lbs., 285/75-16 BFG A/T E load) I run about 35psi which has worked out well so far. Would go down more if only sand but we mostly end up in rocky hard pack so I play it safe by keeping the sidewalls away from the ground.

 

[burn_e]

What kind of sand are you expecting? The pictures shown above all show gravel tracks. Is this what what you will stay on than deflate to the point at when the ride becomes comfortable and the rattle and shake is less. Would guess in your case somewhere around 35psi.

If you are looking for sand as of dunes deflate your tyres until they start deforming - usually 20 psi and below. On my Nissan Patrol I usually start of with around 15 psi. Sometimes it is required to deflate more once the tyres heated up a bit.

 

[morpwr]

I have been lurking for a long time and this is my first post.

I have run a 14,000lb 28' motorhome with 235/75/16 tires on pismo beach with 10 psi front, 8 psi rear. I didn't have any trouble with the tires coming unseated.The rig drove like a tractor, I could drive through soft dry sand without a problem.

This worked fine for a few years, with an occasional blowout, until I upgraded from the firestone R4S to the goodyear g159. The g159 has a steel belt in its sidewall and didn't do well after airing down and re inflation. Two tires popped on the first trip home from the beach and one exploded while parked at the shop. I will never air down tires with steel belted sidewalls ever again.

I would caution against airing down a heavy rig for lots of tire deformation. My tires at 8psi looked almost completely flat but i didn't get stuck. I think the excessive flexing damages the carcass of the tire. Some allterrain tires might be built for this but I found out highway tires that are loaded to the limit don't survive the abuse. Anyway, that's my experience.

 

[drifter_r6]

As most have stated it will depend on your combo (GVW, load, tires, terrain). I have a F350 was loaded to around 11,000lbs with 35x12.5x18 Toyo's E load tires. Was aired down to 25psi in some muddy/rocky terrain. When the truck was on some steep side angles I was really concerned I was going to pop a bead. The sidewalls are really stiff and wasn't flexing enough... if that makes any sense. For me 30-35 is about as low as I want to go.

 

[zonker]

Thanks everyone for your input that you have posted. Airing down on my Fj40.. 109 or Range Rover Classic.. vehicles of years past were much different animals than my choice of transportation these days. If I take all the input and average it together.. I think a great starting point would be 35psi. If I need a little more traction.. 25psi might not be out of the question and pretty solid for bead retention. Going below 25 potentially not such a good choice. So be it.. that is why I am prepared for MaxTrax.. Hi-Lift and X-Jack action!

 

[dblosch]

So, I realize you're asking about the lower end of your safe pressures, But there is some pretty solid information here about general tire pressures vs. volume of air. It's worth a read. Tire Pressures

Dan

:::EDIT::: The article references a chart that was in the original publication. If I can find the issue at home, I'll post some scans later.

 

[Jr_Explorer]

:::EDIT::: The article references a chart that was in the original publication. If I can find the issue at home, I'll post some scans later.

Please. That would be interesting.

 

[dblosch]

:::EDIT::: The article references a chart that was in the original publication. If I can find the issue at home, I'll post some scans later.

Shoot. I totally forgot about this. Writing myself a note for tonight.

 

[Regcabguy]

Thanks everyone for your input that you have posted. Airing down on my Fj40.. 109 or Range Rover Classic.. vehicles of years past were much different animals than my choice of transportation these days. If I take all the input and average it together.. I think a great starting point would be 35psi. If I need a little more traction.. 25psi might not be out of the question and pretty solid for bead retention. Going below 25 potentially not such a good choice. So be it.. that is why I am prepared for MaxTrax.. Hi-Lift and X-Jack action!

I'd consider Load range E tires in the future. Your engine alone weighs 1100# and truck is quite heavy with camper added. Flat resistance is enhanced with the E's also.
I had a near catastropic blowout on I-15 southbound here carrying my popup. Tires were Load range D Bridgestones with a load capacity of 3305 @ 65 psi,well within the load capacity of the rig. Right front blew and within 15 seconds the tire had done $3300 damage to my '98.5 CTD and almost tossed me over the edge into a 200' canyon. Prior to that I got numerous flats and cuts easily. Switched to load range E Toyos seven yrs ago and zero issues since. It's possible to have a flat/blowout with any tire but upgrading to the spec. approved by Dodge should help

 

[Monterorider]

Quoting Factory Owner Manual for 2008 Power Wagon. They recommend 15PSI for sand for stock 285/70R17 load range D BFG AT. Cummins is a bit heavier but not by that much if you distribute the weight. If you are concerned go say 18 PSI.