Off-Road Tire Pressure

[PyrPatriot]

What tire pressure are you guys running when off-road? I know there are LOTS of threads on the topic elsewhere, but the JT is different. They are heavier than the JL and are more off-road capable than any truck. My JT is sitting at 6000lbs! So the tire pressures for a JLU would not necessarily work for me, or anyone here with loaded up rigs, really

Off-roading here in KY is mostly gravel/dirt roads in terrible disrepair that have rocks/roots sticking out of them and lots of puddles/mud spots that can sometimes end up being a couple feet deep! Some stretches have creek crossings that are 20-30" deep and others have climbing up small waterfalls so there are jagged rocks to consider.

I've been doing fine at 22-30psi on 32" mud-terrains, they have not let me down in 10k miles yet (only a few hundred miles off road). C-load tires.

I'll be upgrading to 35x12.50x17 Falken MT01 tires, E-load. I'm thinking of going down to 20psi when I wheel. Their website has the following info for the size

Tire Size	Usage				Load Range C			Load Range D			Load Range E
		35	40	45	50	55	60	65	70	75	80
35x12.50R17LT	Single	2405 (C)	2625	2840	3000 (D)	3065	3130	3195 (E)
LT255/75R17	Single	1870	2055	2230	2405 (C)

Edit: see Falken’s response below

Edit: I deleted exactly what Falken's response confirmed.

For my 255s, there is a 175-185 loss in load per 5psi. So at 25psi I would be at 1600lbs per tire, which is 6400lbs. At 20psi I am at 5600lbs on the 4 tires. I don't think I ever got below 22psi so still good.

For the 37s there seems to be a drastic drop in load capacity at 45psi, dropping 215-220lbs per 5psi. So at 25psi I should be at 1965lbs per tire, at 20psi I'm at 1745lbs per tire, and at 15psi I'm at 1525lbs per tire. So 15psi is as low I could go, on the road, that is. Someone explained it as posted below

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[PyrPatriot]

I was completely wrong on how to calculate the that. From Falken

 

[hjdca]

I have the stock Falken M/Ts. Of Course they do great off-road between 15 and 25 psi (ie. soft terrain, mud, sand).... I have also run them off-road at 37 psi and they do remarkably well in hard terrain.

However, lately, with hard terrain (no more rain), I have been running them on-road and off-road between 31 and 32 psi (cold)... I feel like that is the sweet spot for them - on road and off road (hard terrain).

For just street driving -- probably 34 -37 psi is best...

Rock crawling is a different story -- you need to air down....

 

[PyrPatriot]

Seems like a good explanation. Essentially load considerations go out the window when slow off roading ?

 

[PyrPatriot]

Just for more reference I came up with the following for my upcoming Falken MT01 35x12.5x17 tires
Blank spots means no data was provided. "?" by the number means my estimate.

My conclusion for my own purposes: I can go as low as 15psi and still maintain my vehicle's weight with gear and occupants while off-roading, highways speeds I generally gain 3psi so it will go up to around 20.

 

[SwampNut]

I've spent only a short time on these smaller tires. My previous JKs had 35s and I ran 9-11 PSI any time I was offroad. The stock Falken ATs are horribly harsh above 35 PSI on the road, and teeth-rattling hard offroad above about 18. So I run 34-35 on road (chalk test confirmed this is perfect), and 14-15 any time off the road. I'll do some rock crawling tomorrow, and might try 12-13 depending on how they do at the current pressure.

The lower the better, until you pop a bead or burp a tire. I've never been in a situation off road where more pressure would be better. This is why people run bead locks, to get down to 4 PSI.

 

[PyrPatriot]

I've spent only a short time on these smaller tires. My previous JKs had 35s and I ran 9-11 PSI any time I was offroad. The stock Falken ATs are horribly harsh above 35 PSI on the road, and teeth-rattling hard offroad above about 18. So I run 34-35 on road (chalk test confirmed this is perfect), and 14-15 any time off the road. I'll do some rock crawling tomorrow, and might try 12-13 depending on how they do at the current pressure.

The lower the better, until you pop a bead or burp a tire. I've never been in a situation off road where more pressure would be better. This is why people run bead locks, to get down to 4 PSI.

Right. And I have read that traditional pressure/load requirements dont apply going slow off road. The calculations are for seeing where the pavement worthy pressures meet the trail pressures.

I have done fine at 22psi off road on falken 32s

 

[SwampNut]

Yeah, the load stuff is totally irrelevant off road, unless you're bombing washes at 70, maybe. I never run more than 16 off road.

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