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

[hemiarch]

So a jeep is about what 4000lbs? And a cybertruck around 7000lbs? So on a mass times gravity idea the forces should be quite a bit smaller. Maybe that accounts for the higher pressure recommendation.

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[tmeyer3]

So a jeep is about what 4000lbs? And a cybertruck around 7000lbs? So on a mass times gravity idea the forces should be quite a bit smaller. Maybe that accounts for the higher pressure recommendation.

Not really, the pressure in your tires is determined by the weight of the vehicle and the amount of air in the tire. The bigger factor there is that a jeep is more likely running 35"+ tires on 15" wheels, giving you a lot more room before the bead feels stressed at that pressure than 35" on 20" wheels would. I would comfortably run 25psi on 18" wheels on a CT, but that's going slow, careful, and carrying a full sized spare. I wouldn't exceed 20 mph at low pressures. Losing a bead isn't that big of a deal either, it's annoying, sure, but it's pretty easy to fix. Even so, I always carry a spare because running at lower pressures increases your risk of putting a sharp rock through your sidewall, etc.

If you're wanting to off-road more, I recommend moving to an 18" wheel and running 35"x12.5" tires as they're readily available, generally cheaper (supply is higher), and you can get great off-roading out of them. I don't really consider a 20" wheel to be an off-roading size for these reasons.

 

[hemiarch]

Not really, the pressure in your tires is determined by the weight of the vehicle and the amount of air in the tire. The bigger factor there is that a jeep is more likely running 35"+ tires on 15" wheels, giving you a lot more room before the bead feels stressed at that pressure than 35" on 20" wheels would. I would comfortably run 25psi on 18" wheels on a CT, but that's going slow, careful, and carrying a full sized spare. I wouldn't exceed 20 mph at low pressures. Losing a bead isn't that big of a deal either, it's annoying, sure, but it's pretty easy to fix. Even so, I always carry a spare because running at lower pressures increases your risk of putting a sharp rock through your sidewall, etc.

If you're wanting to off-road more, I recommend moving to an 18" wheel and running 35"x12.5" tires as they're readily available, generally cheaper (supply is higher), and you can get great off-roading out of them. I don't really consider a 20" wheel to be an off-roading size for these reasons.

So how big of a difference would going to 25 psi make over 36psi off-road? Worth the entry cost of downsizing the factory 20’s to 18’s? Let’s say we take beadlock out of the discussion for a moment (although if I was spending the money changing to 18’s I’d probably at least get something “capable” of beadlock mounting)

 

[tmeyer3]

So how big of a difference would going to 25 psi make over 36psi off-road? Worth the entry cost of downsizing the factory 20’s to 18’s? Let’s say we take beadlock out of the discussion for a moment (although if I was spending the money changing to 18’s I’d probably at least get something “capable” of beadlock mounting)

Honestly all these questions come down to preference and that preference comes from experience. I like to buy MTs that are cheap and capable, those don't come in the stock 285/65r20 format. I also don't like spend $400 per tire. So for me, upgrading to 18" wheels was a no brainer because I'd make back the cost of buying new wheels after just a few tire changes.

For reference, I run Armstrong desert dog MTs on an off-road Fittipaldi ft100 wheel. That tire only costs me $200, is amazing off-road, and holds up great on road.

Another option I'm running is maxgrip XTs, a Chinese tire brand that has a great track record for solid hybrid tires. Also around 200 per tire on an 18"

Most folks that demand that a bfg or mickey is the only way to go are just brand zealots.

I would have upgraded to 18s either way, but I can't seem to find good AND cheap off-road tires in 20"...

Anyway, to answer your question I went to 18" to save money and improve performance. I'm rough on tires and I'm fully aware of it. Even so, I expect to get 50k miles out of my Armstrongs with rotating in the spare, I did on my raptor. Unsure about the maxgrips, but for the price I'll happily take 30k miles.

 

[hemiarch]

Not really, the pressure in your tires is determined by the weight of the vehicle and the amount of air in the tire. The bigger factor there is that a jeep is more likely running 35"+ tires on 15" wheels, giving you a lot more room

Honestly all these questions come down to preference and that preference comes from experience. I like to buy MTs that are cheap and capable, those don't come in the stock 285/65r20 format. I also don't like spend $400 per tire. So for me, upgrading to 18" wheels was a no brainer because I'd make back the cost of buying new wheels after just a few tire changes.

For reference, I run Armstrong desert dog MTs on an off-road Fittipaldi ft100 wheel. That tire only costs me $200, is amazing off-road, and holds up great on road.

Another option I'm running is maxgrip XTs, a Chinese tire brand that has a great track record for solid hybrid tires. Also around 200 per tire on an 18"

Most folks that demand that a bfg or mickey is the only way to go are just brand zealots.

I would have upgraded to 18s either way, but I can't seem to find good AND cheap off-road tires in 20"...

Anyway, to answer your question I went to 18" to save money and improve performance. I'm rough on tires and I'm fully aware of it. Even so, I expect to get 50k miles out of my Armstrongs with rotating in the spare, I did on my raptor. Unsure about the maxgrips, but for the price I'll happily take 30k miles.

before the bead feels stressed at that pressure than 35" on 20" wheels would. I would comfortably run 25psi on 18" wheels on a CT, but that's going slow, careful, and carrying a full sized spare. I wouldn't exceed 20 mph at low pressures. Losing a bead isn't that big of a deal either, it's annoying, sure, but it's pretty easy to fix. Even so, I always carry a spare because running at lower pressures increases your risk of putting a sharp rock through your sidewall, etc.

If you're wanting to off-road more, I recommend moving to an 18" wheel and running 35"x12.5" tires as they're readily available, generally cheaper (supply is higher), and you can get great off-roading out of them. I don't really consider a 20" wheel to be an off-roading size for these reasons.

Have you noticed a change in range or in on-road handling or any orher downsides to the setup? 18” seems like the logical way to go by most accounts I’ve heard.

 

[Coagulation]

For those here who have gone down to 25 or lower with the stock AT… what type of terrain were you on, how aggressive were you driving and how did it hold up?

 

[mongo]

For those here who have gone down to 25 or lower with the stock AT… what type of terrain were you on, how aggressive were you driving and how did it hold up?

12 PSI in sand, 60MPH+ on the flats (drag strip area), up dunes, down dunes, over dunes, in circles. Then low speed pavement to the air station. No issues found yet.

 

[Coagulation]

12 PSI in sand, 60MPH+ on the flats (drag strip area), up dunes, down dunes, over dunes, in circles. Then low speed pavement to the air station. No issues found yet.

wow! Thats great to hear. Thats on the stock cyber wheels and AT?

my use case is much slower… and really only needs about 20-25psi

 

[mongo]

wow! Thats great to hear. Thats on the stock cyber wheels and AT?

my use case is much slower… and really only needs about 20-25psi

Yep, stock AT Cyber rims.

 

[WormtownKris]

Have any of you tried the AS tires at full air pressure in fine sand? I have a once per year specific use case and it would be great to know if the truck can do short runs in soft sand without airing down....
Annual guys' fly-fishing trip. Typically, about 8 guys and 2 or 3 vehicles. We've been renting a VRBO on the beach on Lake Ontario for about 8 years running. The last 1000 feet or so to the rental is a beach road- literal tire tracks in the sand along the dunes.
I've taken both my F150s out there. We've had Jeeps, Rams, F150s, Frontiers, Ridgelines, and a Mercedes SUV. NO one has ever aired down. We are in and out a couple of times per day, so airing down and back up would be a major lifestyle change in that environ. One time in very soft sand my friend's Honda Ridgeline *nearly* bogged down. No other issues.
My friends are generally CT curious and supportive, maybe a touch jealous, and maybe a bit wary of the entire EV thing. It will definitely be a litmus test if my heavy-ass CT can do what the others have done. If I get stuck it will be an indictment, without consideration of the 7000# the truck will be hauling.
I've found the truck to be excellent in various snow environments. If I can, this spring I'll try to find a place adjacent to pavement where I can try out sand and where it will be easy to pull it out if needed. But I was hoping to find some reassurance that the weight of this vehicle will not render the CyberTruck less capable than the other vehicles in the crew.

 

[REM]

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.

Excellent info! Would you mind making a new post about your go-to patch kit and minimum recovery gear?

 

[HaulingAss]

Excellent info! Would you mind making a new post about your go-to patch kit and minimum recovery gear?

That's a big topic and what recovery gear you carry will depend more upon where you wheel, solo or not, and how good you are at not needing it. Some people cannot carry enough recovery gear to save themselves, and other people rarely get themselves in trouble. People that mount an electric winch to their truck almost always get stuck at least once right after it's installed. See how that works?

Having said that, a good minimum is a kinetic recovery rope and a tow strap which can double as an anchor point and a few soft shackles. I also like to carry a 3/8" synthetic line (Dynema, Amsteel, etc) of 75'-150' length and a 3-4 ton ratcheting winch (come-along) for solo vehicle trips as a rescue of last resort. A pulley can increase the potential utility of the synthetic line (and the ratcheting winch). 35-40 feet of rigging line with a tough sheath can be handy if you need to improvise an anchor can be handy. Don't forget a recovery point that fits into the 2" tow receiver so you can pull the vehicle from either end and a knife and small shovel.

I don't carry any patch kit, only a tire plug kit and compressor.

More important than the gear above is drinking water, food, clothing, hiking footwear, and shelter suitable for the climate and the longest stranding you can reasonably imagine for where you're at. Because it doesn't matter what you're driving, how many spare tires you have, or how much recovery gear you bring, things can break that leave your vehicle disabled. Travelling with another vehicle can help mitigate that but I often want to explore on my own. If you have reliable satellite or cellular communication, then some of the above gear becomes less essential.

IMO, traction boards are over-rated.

 

[REM]

That's a big topic and what recovery gear you carry will depend more upon where you wheel, solo or not, and how good you are at not needing it. Some people cannot carry enough recovery gear to save themselves, and other people rarely get themselves in trouble. People that mount an electric winch to their truck almost always get stuck at least once right after it's installed. See how that works?

Having said that, a good minimum is a kinetic recovery rope and a tow strap which can double as an anchor point and a few soft shackles. I also like to carry a 3/8" synthetic line (Dynema, Amsteel, etc) of 75'-150' length and a 3-4 ton ratcheting winch (come-along) for solo vehicle trips as a rescue of last resort. A pulley can increase the potential utility of the synthetic line (and the ratcheting winch). 35-40 feet of rigging line with a tough sheath can be handy if you need to improvise an anchor can be handy. Don't forget a recovery point that fits into the 2" tow receiver so you can pull the vehicle from either end and a knife and small shovel.

I don't carry any patch kit, only a tire plug kit and compressor.

More important than the gear above is drinking water, food, clothing, hiking footwear, and shelter suitable for the climate and the longest stranding you can reasonably imagine for where you're at. Because it doesn't matter what you're driving, how many spare tires you have, or how much recovery gear you bring, things can break that leave your vehicle disabled. Travelling with another vehicle can help mitigate that but I often want to explore on my own. If you have reliable satellite or cellular communication, then some of the above gear becomes less essential.

IMO, traction boards are over-rated.

Excellent info, thanks! I've been working on piecing together a kit that isn't overbearing considering this truck is my daily driver, so the most I would probably ever use it would be helping someone else in a bind lol.

Especially good points on survival from being stranded. I always have that in mind. Very soon all cell phones will have access to starlink for emergency situations, so that's going to be amazing.

 

[hemiarch]

So 18 steelies coming soon it looks like. Does having a smaller wheel/bigger tire make it safer to go low pressure or less safe?

 

[HaulingAss]

Have you noticed a change in range or in on-road handling or any orher downsides to the setup? 18” seems like the logical way to go by most accounts I’ve heard.

The 18" rims are better for off-road and price/availability of tires but, obviously, the 20" rims will win out on the pavement (for safety/handling).

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