JHanson said:In general, try about 20 to 25 percent lower than whatever your street pressure is for dirt tracks, 30 to 40 percent lower for four-wheel-drive trails, and up to 50 to 60 percent lower for very soft sand. So if 40psi is normal, try around 30 for dirt roads, 25 for four-wheel-drive tracks, and 20-18 for soft sand.
Of course you adjust for conditions, which was why I Italicized in general. But airing down isn't only about traction. It significantly increases ride comfort over rough roads and trails, and reduces stress on the suspension. It also, importantly, reduces wear and tear on the trail.Wallowa said:I have a slightly different approach....only reduce tire pressure if you can't otherwise get traction..example, White Rim Trail...4X4 for sure but tons of rock; no pressure reduction [E Tires / 60 psi]....higher pressure helps prevention of sidewall and tread punctures...I do this on my dirt motorcycles and Tundra/Hawk...your mileage may vary! Hey, just my way.....
A popular topic on Wander the West -Wandering Sagebrush said:Try this search on Google.
site: wanderthewest.com "airing down"
JHanson said:Of course you adjust for conditions, which was why I Italicized in general. But airing down isn't only about traction. It significantly increases ride comfort over rough roads and trails, and reduces stress on the suspension. It also, importantly, reduces wear and tear on the trail.
I once had to do trail survey work with a guy who refused to engage four wheel drive until his tires were spinning and digging up the substrate. Then he'd refuse to air down until, again, his tires were spinning and digging up the substrate. Better to be proactive.Wallowa said:Ride comfort and damage to roads...never thought about that....
Yep, with the diesel I end up running 60/55 psi F/R, fully loaded. On the washboard of Hole-in-the-rock road I aired down to 45/40. It helped, sort of...Wallowa said:Back to OP's query, I checked the Cooper AT3 load vs psi chart for my size 10ply tires after putting my Tundra and fully loaded Hawk on a truck scale to measure total weight and weight per axle...my sweet spot was 60psi [all four tires], with a heavy diesel front may need more?...don't forget spare...after that as you are so inclined I would go with JH's recommendations on % to air down...if you feel the need.
Chet, I think you are contradicting yourself here. You say personal safety trumps dirt, yet engaging four-wheel drive on a dirt road, even if it's not "absolutely required," increases safety. I understand the value of experience gained with bad tires, etc.—been there—but it's incontrovertible that having traction at all four corners is better—that is, safer—on a loose surface.ramblinChet said:Personal safety trumps dirt every time.
On the trails I am in 2WD and it is nothing short of amazing where a skilled driver is capable of safely taking their vehicle with no damage to the trail. When I find myself in an area that can not be traversed in 2WD it now becomes time to take advantage of 4WD. The next step comes with I engage my front locking differential. The next and final step is taking advantage of a winch.
Mixed in between all of the steps above involves the use of MAXTRAX and other "road building" exercises. If I install a rock somewhere I put it back where I found it once I am through. I am certainly not one of those guys who just presses on the skinny pedal harder when I find myself in trouble - I am a huge proponent of the tread lightly principal.
But I tell everyone I meet there is absolutely no reason to be in 4WD unless it is absolutely required. You are doing yourself and others a disservice by not permitting your knowledge and skills to develop plus you have already eliminated one key safety step if you find yourself stuck in 4WD.
When I began off-roading in the early 90s it was in a Jeep with bald street tires and no lift or lockers. My best buddy was in a 2WD Chevy S-10 with similar limitations. There is something to be said about the knowledge and skill gained and associated with examining a potential obstacle and using your mind to move an object such as your truck through it in three dimensions while taking into account traction, suspension movement, etc.
Vic Harder said:Yep, with the diesel I end up running 60/55 psi F/R, fully loaded. On the washboard of Hole-in-the-rock road I aired down to 45/40. It helped, sort of...
Well, I guess this is just another one of those topics where we will agree to disagree and that's perfectly fine. Different things work for different people. I just tend to go a bit deeper regarding safety issues.JHanson said:Chet, I think you are contradicting yourself here. You say personal safety trumps dirt, yet engaging four-wheel drive on a dirt road, even if it's not "absolutely required," increases safety. I understand the value of experience gained with bad tires, etc.—been there—but it's incontrovertible that having traction at all four corners is better—that is, safer—on a loose surface.