Deflating for comfortable ride

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What is a safe pressure to deflate to when offroading?

Is there a technical means to determine this pressure?

Thanks.
 

deeker

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Without beadlock rims, I wouldn't go much below 12 psi, just so I avoid the risk of unseating a bead on a rock or something.  Typically I would go down to about 20 psi.  You will get better traction due to a larger footprint, as well as a softer ride as the tires deform over obstacles.  You will lose that little bit of ground clearance, if that matters to you.

With beadlock rims, anywhere down to what the sidewalls can tolerate - maybe 6 psi, or even lower.
 

FirewallPhotography

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Thanks, 20psi, using my internal gauge is as low as I have gone and it works real well for improved ride.  I've never had a traction problem to date. (knock on wood).

Thanks for the reply.
 

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Good advice Deeker! I go right down to 12psi. You want to have tires made for it. The BFG Mud Terrains do very well. I've been considering bead locks.
 

Lifestyle Overland

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I had the opportunity to speak with an individual (who shall remain nameless) within the BFG corporation. This particular gentleman was an engineer who helped develop a lot of the tires we run today. He told me (officially) that he can not condone running their tires at a lower PSI than recommended. However, (unofficially) he confirmed that running at a lower PSI under the right circumstances would not degrade the integrity of the tire itself.
That being said; there are several factors to consider when selecting a proper PSI... this was some of his input on the subject:

1) Wheel size versus overall tire size.

So how much meat (rubber) do you have between the rim and the rock you're about to hit? If you're running 15" wheels with 35 or 37 inch tires you can go down in the 10 PSI range with no issues. If you're trying to run 18" wheels then 20 PSI is probably as low as you want to go if there's a chance you'll tag a rock. The reason for this is you can actually damage the interior of your tire if you were to pinch the tire between a rock and the rim. This type of damage will go unnoticed until you either remove the tire, or have a blowout...

2) Speed.

The rate at which the tire deforms and reforms can have an adverse affect on the sidewall as well. If you're running 55 MPH down a paved road to a trail head at 18 PSI you're generating a ton of heat due to the constant deforming and reforming of the tire footprint. It doesn't take long to do irreparable damage to a tire under these conditions (which is also hidden to the user). Consider airing up even if it's just a short run down a hard surface at speed.

3) Surface.

This factor goes hand-in-hand with speed. The type of surface you're running on can make all the difference on PSI selection. For example, if you're running on sand, the surface itself is helping support the integrity of the tire since it is also deforming to accept the footprint of the tire. You can typically run much lower PSI on sand due to this fact. Rocky trails at slow speeds are also good candidates for lower PSI since you want more deformation to avoid a puncture or cut. Gravel roads would be a bit less forgiving especially if they are hard packed. Consider a medium range PSI.

4) Aggressiveness of steer.

Basically this means; how hard will you been cutting the wheel at speed? You can run 2-5 PSI in sand... in a straight line. If you plan on doing donuts then you're probably going to blow a bead... and possibly roll your rig if you're carrying enough speed. Same for rock crawling, if you're at an extremely low PSI and try to cut hard while in a bind, you're likely to blow the bead.

The final decision on PSI is really up to you. It's your rig, so experiment with different settings until you find those sweet spots for your unit's wheels-to-tire size ratio and final weight. I highly recommend investing in some quality deflators (Stuan or ARB) and a 100% duty rated air compressor (Dual compressor ARB unit is incredible) to save a lot of headache and time. Also, get a quality air pressure gauge... that free one from NAPA ain't no good! (After tons of research I got a digital craftsman unit from amazon)

And if you do blow a bead... try a heavy duty ratchet strap (kept in the tool kit) for wrapping around the tire while re-seating.

Here are my typical PSI settings for our 2014 4Runner running BFG KO's in 275/70R17 Load Range E:

Every day travel: 40 PSI front 42 PSI rear (45 PSI in rear if loaded)

Highway between trails: 30-32 PSI (Used this in Colorado since our route had highways in between trail heads)

Gravel Roads: 20 PSI (24 PSI in rear if loaded)

Rocky Trails: 16 PSI (18 in rear if loaded)

Sand: 14 PSI (18 PSI in rear if loaded)
 

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Uh, I here a PSA in order...gonna make that happen.
 

maktruk

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Also remember your load range determines how much the sidewall will flex. High load range tires will have a harder time conforming to the surface and can blow a bead by folding over the rim.
 

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Michael, where did you get those cool deflators you use in your video? That seems like a good devise if you know you want to go to a specific pressure quickly.
 

rmerron

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Thanks. I'll pick some up. The wife and I are building up her 4Runner. Decided to sell the house and our stuff. Take a year off and tour US, Canada, Alaska. Hope to be ready within the next 4-6 Months. We have been 4wheeling and camping in the FJ, but your site and XOverland has gotten us both excited. She had breast cancel 5 years ago, I got really busy in Business, its time to do what we want, stuff be damned. Our kids are grown, have grandkids but we want to travel before we are too old. I was planning on showing the build on the forum. Planning on visiting some of the areas you highlight in California. Going to hit all of the National Parks. Think it going to be awesome. Also finishing up an off road trailer. We are going to the Expo in Asheville in a few weeks. Getting some ideas for the rig. Take care and keep it up. Ralph
 

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WOW! What an awesome adventure. Enjoy it as much as possible! Thanks for letting us know. It means a lot to know some people are encouraged by some of the stuff e are doing!

Let us know as your adventure develops!

M
 

Michael

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Michael, where did you get those cool deflators you use in your video? That seems like a good devise if you know you want to go to a specific pressure quickly.
Hey rmerron I ust Staun. They are the spendy version, but I've had both and recommend spending the extra coin: Tire Deflators
 

4xFar Adventures

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I've used Staun's for years. The best approach is to start at a higher, lower PSI (if that makes sense), and run a trail and see how it feels for you. It's easy to drop ~5PSI if the ride still feels a bit rough. Of course, it will help if you're familiar with the trail and expected terrain. If it varies greatly, you may wind up having to air up and down a few times. If you run CO2, you're less likely to add pressure, only to release it a little later.

I've run 18PSI going 35mph on pavement. I won't go any faster than that, and only for about 10 miles.

Everything @stringtwelve mentioned is spot on. Even a simple fire road, where you have more than sufficient traction, can benefit from a lower PSI by smoothing out the ride handling. Remember, the tires are the first part of the suspension system. That larger footprint can make it a little more difficult to steer on a surface like slickrock.

This of course opens the can-o-worms argument, "Which is better, CO2 or a compressor?" for re-inflating. I'll leave that for another thread.
 

MVO

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What is a safe pressure to deflate to when offroading?

Is there a technical means to determine this pressure?

Thanks.
I was just scanning through posts when I come across the often talked about tire pressure question. At Overland East I did the BF Goodrich drive with a company engineer. He warned me that lowering the pressure would lower the tires ability to fend off punctures. So be careful out there.


Sent from my iPad using OB Talk
 

The other Sean

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I was just scanning through posts when I come across the often talked about tire pressure question. At Overland East I did the BF Goodrich drive with a company engineer. He warned me that lowering the pressure would lower the tires ability to fend off punctures. So be careful out there.


Sent from my iPad using OB Talk
That's an odd statement. While running at a lower PSI will mean you are running a little bit on the sidewalls exposing them to things, but, the lower internal pressure means less chance of actual puncture. Think of a balloon being inflated a little or a lot. the one inflated a lot is easier to pop. I think that engineer's answer was a little oversimplified.