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I just recently purchased an 07fj with lockers, atrac and am planning on going off-roading on boxing day.

I have new Bridgestone destination LE's on it (From the dealership). Anyone have any recommendations on airing down to get increased grip with all season tires? The terrain will mostly be old forest service roads and maybe a little bit of snow.

Thanks in advance
 

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I bet you can air down to 18 PSI... If you were in some rocky spots I'd say nooo...don't want to break a bead and maybe rim damage...But for what you intend to do...You can air down low and be O.K. just my .02...
 

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I've had em down to 5 in hawaii, the stock dunlops. it was all soft sand and slow driving so I wouldnt recommend it for any other terrain or speeds.
 

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Some Doc posts on the matter...


My take on it is that you really shouldn't be running 5 to 15 psi on any tire that you'd dual use for road and off road. Those pressures are for off road only tires that are designed with significantly more sidewall than a road tire.

Also, with the FJ Cruiser's low slung belly, you're going to sacrifice critical amounts of ground clearance when you go that low.

The fully laden FJ Cruiser is about 5000 pounds. It's a heavy beast. At that weight and (I'm guessing) a 60/40 front to back weight ratio, you've got around 1500 pounds on each front corner and a grand each side in the rear. 1500 pounds divided by 20 pounds per square inch is 75 square inches.

That's a really big contact patch already.

For most 35" tire designs I've seen, my belief is that you're not going to get much better behavior out of them going below 15. At 15, cupping and wadding is already going t be a problem in some circumstances. I ran 20 for most rock trails and kept that last 5 in reserve for specific applications. Below 20 and the loss of ground clearance starts to become a big sacrifice.

By the way, even for those pressures, I'd also say that if you're not using a tread design that totally sacrifices road behavior, then you're just kidding yourself. "All-Terrain" designs are basically road tires (much more lug than void, and circumferential grooving rather than cross-ways) with no side biting lugs to speak of. Airing these critically low only causes cupping and lays smooth sidewall down on the ground, to be sacrificed by the rocks.

In general, the tires that benefit from low pressure have large void spaces between the lugs, a gear-tooth-like groove pattern so that the lugs tend to grip together as the tire is pushed concave by rocks, and side biting lugs that wrap way around the sidewall.

In general, these are the same tires that howl like coyotes in the night when you get above 35 mph on paved roads.

People pursue low tire pressures like it's some sort of holy grail. It becomes a number without significance unless you attend to the individual behaviors of the tires. It's different brand to brand, condition to condition, and front to back. I suggest to pick a tire by whatever means you want (looks, name, recommendation, previous experience... whatever) and then experiment with it for optimization. Don't become a tire brand loyalist. Be ready to be surprised. Be ready to like a tire when you get it and change your mind about it later. There's a lot to the black art of tire construction and proprietary rubber manufacturing. Similar looking tires behave differently.

As far as pressures go, for 35" tires on 16 or even 17" rims, there's not really enough sidewall to let it get down too low. The behavior of the sidewall with pressure too low becomes a tendency to pinch and fold. You can get the tire to wad up and crease on obstacles instead of conform. If you point load it badly, it'll actually drive the edge of the rim into folded sidewall and start a tear. If you get really unlucky, you'll get it to wad up under the edge of a rock or a root and as you drive by, and you'll lever open a tear like a can opener. That's basically a tire fatality. A lot of perfectly good tires with tons of tread life die early deaths due to sidewall puncture.

It's worth avoiding, if possible. These tires aren't cheap.

If you drive an off road only buggy that gets trailered to and from the trails, you can get *some* big sidewall tears patched and vulcanized at select tire shops that basically service giant earth mover tires. However, they won't touch a DOT tire that goes on a car that travels on the road.

My advice is that if you want to run 35's, start by choosing a tire and putting it on a steel rim. You're going to have some work to do customizing your wheel wells to get the tire to clear in all circumstances. Work on that first. Get used to snapping some CV axles and doing change-outs. Play with tire pressures of 25, 20 and sometimes 15. Remain skeptical and force the car to prove to you that it's doing what you want.

Later, figure out whether or not you need beadlocks.

BTW... super low pressures are for rock crawling. Super light rims are for minimizing the moment of inertia so that changes to angular velocity (wheel rpm) can be effected with less torsional force. That's a thing for going fast and changing speeds frequently. Go-fast tire pressures are not low.
If a CV axle doesn't snap, the next failure up the line involves ring and pinion teeth. This is a particular disaster because the broken shards get chewed on by the differential and that can be destroyed too. Axle failure seems to happen at the outer joint. It happens at full lock and full droop, with the front end locked. I have yet to hear about an axle shaft or inner joint snapping, but that doesn't mean it hasn't happened. It usually the race that holds the bearing balls together in the birfield joint. It blows, the balls eject, and the axle spins without the wheel.

DOT Pitbulls are probably a really good choice because they care about sidewall construction, at least in the 40+" sizes, and I would expect no less in the smaller tires. They have pretty wide tire designs, so be ready to do a lot of fabricating. Your wheel well will need more than just a little trimming.

I wouldn't run 33" tires at 15-20 psi normally, so I don't know what to tell you about "almost losing a bead". 33" tires are usually really more like 31.5 or 32" (sometimes smaller!) and with a 17" rim, that gives you only about 7" of sidewall with half an inch of tread height. If you run pressures that low, you're deforming rubber REALLY close to the bead. Pitbull Rockers may be closer to true measurements and if you run the 35" tire on a 16" rim, you'll have a lot more sidewall surface to exert the air pressure on from the inside. For added insurance, mount the tire with a little Gorilla glue on the bead. ;)
 

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fka trailman
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i go 12-15 psi no problems
 

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I was on a fairly rocky (but still stock friendly) outting today. A guy with 20 years of experience in these matters suggested I take my OEM 265/70-17's down to 15 pounds.

I think it was a great idea.

The ride was smooth(er) and while I lost maybe 1/2" of clearance (maybe a bit more, but acceptable) there was no sidewall on the ground, and no tire spinning either, even in the thick/wet mud. I'm planning on doing this regularly. I don't *think* I was anywhere near losing the bead.
 

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I recently took the FJ out for a little Mud Spa day. AIred my Nittos muds down to 20psi.... by looking at the truck you couldnt tell they were aired down! You could notice it took bumps and rougher terrian smoother and got alot more traction in the slippery stuff....
 

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I recently took the FJ out for a little Mud Spa day. AIred my Nittos muds down to 20psi.... by looking at the truck you couldnt tell they were aired down! You could notice it took bumps and rougher terrian smoother and got alot more traction in the slippery stuff....
X2

Even at 15/16 lbs you had to look twice to tell my p.o.s. OEM tires were aired down.
 

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10 no problem here
You run 10PSI with the stock highway tires in all conditions and have 0 problems???

The sidewalls on the stock tires are horribly weak and thin.

Maybe in sand or snow they might be okay, but still pretty low for those tires.
 

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X2

Even at 15/16 lbs you had to look twice to tell my p.o.s. OEM tires were aired down.
I knew the Mud Grapplers were tough but I really didnt expect the Sidewalls to be that Strong ... Im told I can go as low as 8psi with out bead locks and 3 with.... Maybe I can!
 
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