How low do you deflate stock AT tires and wheels for off-roading?

[hemiarch]

So the manual recommends not going below 36psi. I have done this. Not that enormous of a difference to me. Ride is a little nicer. Hard for me to tell how well I would have handled the obstacles if I had stayed at 50psi.

Apparently the $550 compressor has a preset for 18.5psi. Never tried this.
How low is safe and or useful? What’s the downside?
Any insight would be appreciated.

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[Kryptek]

You dont want to damage your wheel, lowest tire psi i would do is like 33 remember 7k with a driver in weight

 

[Coagulation]

The recommended 36 feels not that low but I’d stick that that for most applications.

I do wonder what the guys who did Glamis / other sand driving aired down to. 36 is high for sand and there’s far less wheel risk in sand vs rocky terrain for example. My biggest concern would really be losing bead.

 

[HaulingAss]

So the manual recommends not going below 36psi. I have done this. Not that enormous of a difference to me. Ride is a little nicer. Hard for me to tell how well I would have handled the obstacles if I had stayed at 50psi.

Apparently the $550 compressor has a preset for 18.5psi. Never tried this.
How low is safe and or useful? What’s the downside?
Any insight would be appreciated.

Tires are not just rubber air bladders, they have Kevlar and steel and other low stretch fibers embedded in the rubber to control the substantial forces they need to resist as they drive. For good handling on-road, these reinforcements go through the sidewall, across the tread, and through the opposite sidewall at various angles to handle forces from different directions. The reinforcements help keep the tread in flat contact with the pavement when cornering and travelling sidehill.

Underinflating can overwork the fibers, causing fatigue failure from repeated flexing. It can also cause microscopic micro-tearing of the rubber around the fibers (because the rubber wants to stretch and the fibers don't). This can turn your tires into junk in short order but the damage is cumulative and irreversible. It can also greatly increase your chances of flats and blowouts as the tires get older, even if subsequently inflated fully for road use.

True off-road tires have less structure, they are more like an agricultural tire that is designed to be run at low psi and thus deform more, conforming to the terrain. That is why they are not suitable for on-road driving. They absolutely suck at cornering. None of the OEM tires offered by any manufacturer I am aware of are true off-road tires, they would suck on public roads and be unsafe as well.

There is no hard line as to what pressure is unacceptable, it depends upon how much you are willing to increase the chances of flats down the road, how much you appreciate the fine handling on-road of your tires as delivered and how much you want to risk a flat on the trail or even a de-beading of the tire from the rim.

The 36 psi suggested by Tesla as the minimum pressure is probably a good limit to avoid most problems in general, but it's not really low enough for maximum off-road capability, particularly on soft surfaces like sand, spring snowpack, thick mud, etc. Nor is 36 psi a high enough pressure to avoid tire degradation and damage at all speeds and loads.

Operators should consider how heavily loaded the truck is. A truck full of adult passengers, loaded to it's maximum GVWR with all kinds of camping and survival gear, food and water, etc. needs to maintain higher tire pressures than a vehicle lightly loaded on a day trip with one or two people. I suspect even 36 psi can have detrimental effects on the tires if loads and speeds are high enough, and enough miles ore covered. On the other hand, on a soft conformable surface like sand or deep snowpack, at slow speeds, and for relatively short distances, you can probably get away with much lower pressures without any noticeable tire degradation once you air back up.

Just use some common sense, don't go below 36 unless absolutely necessary (and only as far as necessary), and keep speeds slow when aired down. If you get stuck in some particularly fine sand, deep snow or mud, etc., it's often a good idea to air down, maybe as low as 15 psi to get unstuck, and then air back up immediately. I use 40 psi a lot for general off-road driving because there is limited downside at slow speeds and significant benefit in ride quality and traction on irregular surfaces. It will feel much like the 50 psi typically used on road, but the tires just work better at slow speeds with 10 psi less. 36 psi feels even better on rugged rocks (and 30 psi feels better yet) it's just a matter of how much you value your tires and tire reliability (both on-trail and after you re-inflate).

Don't get lazy about airing back up when you no longer need the low pressures. I don't carry a spare tire because I know how to avoid flat tires. I only carry a plug kit for emergency puncture repairs. So I avoid over-straining the reinforcements in my tires that very low pressures or extended freeway running on tires aired down moderately can cause. If you are willing to accept a higher incidence of flat tires, blowouts, and poorer performance that can result, even after airing them back up, then go ahead and break the rules of thumb. I value reliability and have found 36 to 40 psi to provide significant benefits off-road while having acceptable impacts to tire reliability, performance and longevity.

One solution would be to have dedicated off-road tires that you can trash with low pressures and are swapped out whenever you want more bombproof freeway reliability from flats and good road safety and cornering performance. Most people will be happy avoiding the abuse of their OEM AT tires (by avoiding very low pressures and/or high speeds) and using the same tires for everything. Really, ultra-low pressures, like below 15 psi, should only be used on true off-road tires designed for slow speeds and low pressures. This holds true even if you are wiling to cause permanent damage to your higher speed AT tires (unless you are also fine with a lot of on-trail tire failures). The carcass of an AT OEM tire for the Cybertruck is pretty stiff for good reasons, they just aren't designed to be aired down to very low pressures.

 

[mongo]

So the manual recommends not going below 36psi. I have done this. Not that enormous of a difference to me. Ride is a little nicer. Hard for me to tell how well I would have handled the obstacles if I had stayed at 50psi.

Apparently the $550 compressor has a preset for 18.5psi. Never tried this.
How low is safe and or useful? What’s the downside?
Any insight would be appreciated.

The Tesla compressor includes a slime style fix pack also. The inflation/ deflation feature is nice, but the system is slow, especially if doing all four tires. I have a 4 way hose set with gauge and dump valve along with an AC (bed) powered pancake compressor.

36 psi is the Tesla recommendation, Wes unmounted a tire at 25 psi.
A few of us have dropped them to 12psi to go on sand dunes. No ill effects seen yet, but it is harder on the sidewalls.

 

[hemiarch]

Tires are not just rubber air bladders, they have Kevlar and steel and other low stretch fibers embedded in the rubber to control the substantial forces they need to resist as they drive. For good handling on-road, these reinforcements go through the sidewall, across the tread, and through the opposite sidewall at various angles to handle forces from different directions. The reinforcements help keep the tread in flat contact with the pavement when cornering and travelling sidehill.

Underinflating can overwork the fibers, causing fatigue failure from repeated flexing. It can also cause microscopic micro-tearing of the rubber around the fibers (because the rubber wants to stretch and the fibers don't). This can turn your tires into junk in short order but the damage is cumulative and irreversible. It can also greatly increase your chances of flats and blowouts as the tires get older, even if subsequently inflated fully for road use.

True off-road tires have less structure, they are more like an agricultural tire that is designed to be run at low psi and thus deform more, conforming to the terrain. That is why they are not suitable for on-road driving. They absolutely suck at cornering. None of the OEM tires offered by any manufacturer I am aware of are true off-road tires, they would suck on public roads and be unsafe as well.

There is no hard line as to what pressure is unacceptable, it depends upon how much you are willing to increase the chances of flats down the road, how much you appreciate the fine handling on-road of your tires as delivered and how much you want to risk a flat on the trail or even a de-beading of the tire from the rim.

The 36 psi suggested by Tesla as the minimum pressure is probably a good limit to avoid most problems in general, but it's not really low enough for maximum off-road capability, particularly on soft surfaces like sand, spring snowpack, thick mud, etc. Nor is 36 psi a high enough pressure to avoid tire degradation and damage at all speeds and loads.

Operators should consider how heavily loaded the truck is. A truck full of adult passengers, loaded to it's maximum GVWR with all kinds of camping and survival gear, food and water, etc. needs to maintain higher tire pressures than a vehicle lightly loaded on a day trip with one or two people. I suspect even 36 psi can have detrimental effects on the tires if loads and speeds are high enough, and enough miles ore covered. On the other hand, on a soft conformable surface like sand or deep snowpack, at slow speeds, and for relatively short distances, you can probably get away with much lower pressures without any noticeable tire degradation once you air back up.

Just use some common sense, don't go below 36 unless absolutely necessary (and only as far as necessary), and keep speeds slow when aired down. If you get stuck in some particularly fine sand, deep snow or mud, etc., it's often a good idea to air down, maybe as low as 15 psi to get unstuck, and then air back up immediately. I use 40 psi a lot for general off-road driving because there is limited downside at slow speeds and significant benefit in ride quality and traction on irregular surfaces. It will feel much like the 50 psi typically used on road, but the tires just work better at slow speeds with 10 psi less. 36 psi feels even better on rugged rocks (and 30 psi feels better yet) it's just a matter of how much you value your tires and tire reliability (both on-trail and after you re-inflate).

Don't get lazy about airing back up when you no longer need the low pressures. I don't carry a spare tire because I know how to avoid flat tires. I only carry a plug kit for emergency puncture repairs. So I avoid over-straining the reinforcements in my tires that very low pressures or extended freeway running on tires aired down moderately can cause. If you are willing to accept a higher incidence of flat tires, blowouts, and poorer performance that can result, even after airing them back up, then go ahead and break the rules of thumb. I value reliability and have found 36 to 40 psi to provide significant benefits off-road while having acceptable impacts to tire reliability, performance and longevity.

One solution would be to have dedicated off-road tires that you can trash with low pressures and are swapped out whenever you want more bombproof freeway reliability from flats and good road safety and cornering performance. Most people will be happy avoiding the abuse of their OEM AT tires (by avoiding very low pressures and/or high speeds) and using the same tires for everything. Really, ultra-low pressures, like below 15 psi, should only be used on true off-road tires designed for slow speeds and low pressures. This holds true even if you are wiling to cause permanent damage to your higher speed AT tires (unless you are also fine with a lot of on-trail tire failures). The carcass of an AT OEM tire for the Cybertruck is pretty stiff for good reasons, they just aren't designed to be aired down to very low pressures.

Thank you. That’s exactly the kind of answer I was hoping for. I feel better educated after reading it.

 

[hemiarch]

So how does beadlock allow you to go lower? That seems to be what the marketing material is saying when I read it.

 

[BrockN]

This is a question I have been pondering. In my case, I'm more interested in a realistic safe minimum pressure for short distances in difficult conditions that really need lower tire pressure. Not an 'aggressively drifting in dunes' sort of situation! My interest is what that lowest pressure would be given these aren't bead lock wheels.

I'm not as worried about tire life, because this would not be a regular occurrence and certainly not for significant distances.... more a case, of 'how low can I go if I'm desperate to get out of a tough situation'?

 

[BrockN]

So how does beadlock allow you to go lower? That seems to be what the marketing material is saying when I read it.

The wheel is designed to clamp the tire bead in place so it can't slip away from the rim and deflate. So the seal isn't reliant on having enough air pressure in the tire to push the tire bead against the rim.

 

[hemiarch]

But that still doesn’t negate all the tire stress stuff discussed above right? Just the risk of “de…tiring” I guess.

 

[BrockN]

But that still doesn’t negate all the tire stress stuff discussed above right? Just the risk of “de…tiring” I guess.

Yeah, it definitely doesn't prevent the typical low pressure wear and tear to the tire - it's just to keep the tire in place so you don't end up with an ultra low tire pressure... of zero psi...

 

[hemiarch]

Dumb question, is there a downside to the beadlock thing? Like on the road for example?

 

[BrockN]

Dumb question, is there a downside to the beadlock thing? Like on the road for example?

Where I am they aren't legal for on-road use, at least as far as I know. They're heavy, clunky wheels that don't balance as easily as 'normal' wheels. Probably bad for range. And if they lose a bolt or bolts at speed, that would probably be pretty dangerous for anyone in the vicinity of the flying bolt and even the driver if the tire lost pressure instantly. They're typically used by serious off-road folks who probably trailer their ride to the end of the pavement.

 

[HaulingAss]

But that still doesn’t negate all the tire stress stuff discussed above right? Just the risk of “de…tiring” I guess.

Exactly. A beadlock just increases reliability WHILE aired down by eliminating the possibility of de-beading a tire.

Pressures below 30 psi (on a wheel without beadlocks) will greatly increase the chances of de-beading, but the driver can mitigate it to some extent by driving in a manner that is less likely to debead.

The catch-22 is that some of the situations that may cause one to want really low pressures are very difficult to navigate while avoiding the kind of forces that will cause a de-beading (like rock-crawling). On the other hand, fine deep sand or deep sloppy old snow do not tend to cause debeading as readily, because they support a partially deflated tire more evenly. That helps the bead stay sealed. Sometimes at lower pressures a tire will not de-bead completely, but it will lose a bead long enough to "burp" some air pressure out of the tire. The tire is now more deflated and even more prone to de-beading if you continue to drive without re-inflating it.

Still, I will always err on the side of too much air pressure vs. too little. Reliability is more important to me and I can generally use driver skill to get through a tricky spot rather than relying on ultra low pressures.

 

[Gaximus]

When I go off-roading in my jeep, I air down to 12 psi, without bead lockers. And never had an issue. I also do more of a rock crawling style so I’m not taking turns a high speed.

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