Tyre pressure for sand, mud, rock and corrugated roads

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Tyre pressure for sand, mud, rock and corrugated roads

Post by Wes » 16 Sep 2016, 10:25 am

Hi guys,

Would like to know peoples thoughts on tyre pressures for the various surfaces you face in 4WD. I'm got a bit of experience on some of this, little on others, so half is personal opinion, half is from reading what seems like general consensus.

First, truck only. Assume a bit of gear weight and possible 2 - 3 people. NOT towing anything to start.

My current thinking/testing is:

Bitumen: 40 psi
Gravel roads: 40 psi
Soft sand: 18 psi normally (drop to 12 psi to get out of a real bad spot)
Firm sand tracks: 25 psi
Mud: 25 psi
Rocks: 25 psi (drop to 20 psi if real treacherous)
Corrugated roads: 35 psi

Towing? Do you change? I have no idea. What do you do?

(Blank template below to copy for your reply)

Bitumen:
Gravel roads:
Soft sand:
Firm sand tracks:
Mud:
Rocks:
Corrugated roads:

:thumbsup:
Last edited by Wes on 14 Nov 2016, 2:20 pm, edited 1 time in total.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by AusTac » 16 Sep 2016, 11:35 am

For a 2 door jk wrangler usually lightly loaded with some recovery gear and such

Bitumen: 34 psi when tyre is cold
Gravel roads: 24ish hot
Soft sand: don't like or have any sand
Firm sand tracks: -
Mud: 18 if its really sloppy
Rocks: 18ish for rocks in low range
Corrugated roads: about 25 hot

Can vary though depending on how bad stuff is

Sometimes i dont even air down if i'm only passing through on hard packed roads
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by on_one_wheel » 16 Sep 2016, 1:59 pm

This is generally how I run my patrol with 265/70 17 BF Goodrich A/T's
Highway, 40psi 45psi loaded
Very rough road / corrugated ~ 25 / 35
Soft sand 15 / 25

I've had my pressures lower in the sand before but only when I'm in trouble.

No need to change for towing unless you have excess weight on the drawbar, in that case I'd add some pressure to the rear.

Obviously different tyres behave differently, number of plys, sidewall stiffness, strength & protection all affect how you'd run them.

I'm always cautious about how fast I travel with the pressures low. Tyre failure from heat is always on my mind as well as peeling them off the rim.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by OODAH » 17 Sep 2016, 12:07 pm

on_one_wheel wrote:This is generally how I run my patrol with 265/70 17 BF Goodrich A/T's
Highway, 40psi 45psi loaded
Very rough road / corrugated ~ 25 / 35
Soft sand 15 / 25

I've had my pressures lower in the sand before but only when I'm in trouble.

No need to change for towing unless you have excess weight on the drawbar, in that case I'd add some pressure to the rear.

Obviously different tyres behave differently, number of plys, sidewall stiffness, strength & protection all affect how you'd run them.

I'm always cautious about how fast I travel with the pressures low. Tyre failure from heat is always on my mind as well as peeling them off the rim.



I'm the same on my new hilux, same size and BF Goodrich KO 2's. Take note Wes on your tyres too when your letting them down that you can expose the side wall to damage. Most Aggressive at's and mud tyres will have stronger sidewall technology and also side biters to prevent this.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Die Judicii » 17 Sep 2016, 10:53 pm

Some of you guys amaze me with your ideas for tackling soft sand.

So long as you are running tubeless, my past experiences dictate the following.

> soon as getting to soft sand, drop pressures to a starting point of 15 psi
> if that doesn't spell success, drop pressures again, to 12 psi
> etc etc till you get success.
> as long as you are in pure soft sand without rocks you can go for broke.

I actually ran so low once that two tires have come off the bead,, but it drove out.
No damage done, it was a simple matter of re-inflating the tires and popping them back into place.

In mud, it is also advantageous to lower the pressures.

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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by BBJ » 19 Sep 2016, 10:26 am

Die Judicii wrote:In mud, it is also advantageous to lower the pressures.


Do you have much experience in mud? (I don't)

I read contradicting reports on this. Some that lower is better, for obvious accepted reasons.

Others that keeping it significantly higher than sand (25psi?) is better as you want the rigid enough that you can spin your wheels to dislodge mud rather than have it stick in the tracks.

And also to avoid hitting a bank in the mud and popping the tire off the bead due to too-low pressure.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by AusTac » 19 Sep 2016, 12:44 pm

BBJ wrote:Do you have much experience in mud? (I don't)


The trick is just being aware/understanding what you've done to the tyre when lowering it, in terms of rigidity, heat from speed, and trying to look after your sidewalls, if your down low ( under about 15 ) i certainly wouldn't be asking to much of my tyre in regards to boucing off rocks and getting the right foot into it

But yeah in my experience i'm a firm beleiver in airing down for mud
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Die Judicii » 19 Sep 2016, 9:05 pm

AusTac wrote:The trick is just being aware/understanding what you've done to the tyre when lowering it, in terms of rigidity, heat from speed, and trying to look after your sidewalls, if your down low ( under about 15 ) i certainly wouldn't be asking to much of my tyre in regards to boucing off rocks and getting the right foot into it

But yeah in my experience i'm a firm beleiver in airing down for mud


The scenarios that I have had a lot of experience with,,, (real loose and deep sand) and negotiating it successfully don't include high speed, and rocks were very few and far between.

Driving in this manner you have to be extremely watchful none the less.
And, your more likely to have an engine heating problem due to the heavy going,,,, than you would tires overheating.

Besides, I don't drive all day with the tire pressures way way down.
As soon as the conditions allow, I increase the pressures till they have to go down again.
A good set of deflaters makes the job quicker and easier.

I built and mounted my own belt driven air compressor that would fill the air tank to 150 psi, and would pump all 6 tires
(trailer and vehicle) from 10 or 12 psi back up to 40 psi in just on 10 minutes.
Having a passenger removing and replacing valve caps as you work around the vehicle also helps speed up the process.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Lorgar » 20 Sep 2016, 11:39 am

BBJ wrote:Do you have much experience in mud? (I don't)

I read contradicting reports on this. Some that lower is better, for obvious accepted reasons.

Others that keeping it significantly higher than sand (25psi?) is better as you want the rigid enough that you can spin your wheels to dislodge mud rather than have it stick in the tracks.

And also to avoid hitting a bank in the mud and popping the tire off the bead due to too-low pressure.


Higher PSI being required to spin mud off doesn't make sense to me.

The theory makes it sound like the whole tire sags, which it obviously doesn't, and traps mud in the collapsed tread. Even an un-inflated tire retains it's shape and the tread is 'open' as usual.

Obviously the bottom portion of the tyre that's contacting the ground will be deformed in line with the amount of pressure, and you're throwing mud off the remaining 80% ish of the tires exposed surface from the taut top and sides.

Increasing the pressure would reduce the foot print, and increase the taut surface area of the tire but it seems like a minuscule gain in the taut area for the purposes of 'mud-throwing' in exchange for what would be a relatively high loss in traction from the reduced foot print.

And a less malleable footprint for forming to the surface below.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by tom604 » 20 Sep 2016, 1:52 pm

aahhh mud everyone's right :shock: it all depends on the base/thickness, hard or soft or quicksand, you may want them hard to cut through the top layer of slop to get to the firm stuff, think snow chains, sand, down to 20,gives you plenty of room to go down, rocks the same or less all depends on the rocks and go slow "ish" you want your tyre to mold? to the rock. it's a bit like how long is a bit of string, it all depends on a lot of factors. most hills you can crawl up, others you need a bit of right boot :unknown: :thumbsup:
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by happyhunter » 20 Sep 2016, 7:05 pm

13 PSI on the sand.
16-20 PSI in the mud.
20-25 PSI on rocky stuff.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by franc » 26 Sep 2016, 11:26 am

Get a mate with another 4WD and head to the beach.

Take it in turns getting stuck so someone is free to pull out the other and try a range of pressures :thumbsup:
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Flash » 10 Jun 2017, 5:55 pm

It's an interesting topic.
I find people are far too afraid to lower their pressures and I fail to understand why.

My bitumen pressure in my 80 series is 40psi. I want low rolling resistance. I run 33 inch skinny muddies. 4.2Ltr turbo diesel "loaded" gets 12litres/100 highway.
The moment I'm off bitumen and onto dirt tracks, I'm down to 20-25psi for a nice comfortable ride.

We do a lot of 4wd'ing around Walhalla, Aberfeldy, Mansfield, Jamieson.

Once we're about to do tracks, it's straight down to 16psi. We, or anyone we've gone with, has never had a bead come off the rim.
The rocks are sharp and having lower pressures not only improves grip, but prevents punctures. In the cooler months, the clay is wet and slippery.
One time, one couple who came along was having trouble with a section that no-one else did (poor tyres), so dropped the pressure to 10psi. We still had to winch in the end, but the low pressure didn't cause the bead to break.

(I just looked at the original post again who said he runs 35 on corrugated). 35 on corrugated is way too high. Go 25 there.

Don't be afraid to drop the pressure. On low pressure, you drive slow, never fast.
Even when I'm on 16psi and we've done a track, and then go on a normal dirt road to get to the next exciting track, we only cruise along at 20 - 30klm/hr (50 if it's wide and straightish) . What's the hurry?
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Lorgar » 13 Jun 2017, 11:09 am

Flash wrote:My bitumen pressure in my 80 series is 40psi. I want low rolling resistance. I run 33 inch skinny muddies. 4.2Ltr turbo diesel "loaded" gets 12litres/100 highway.


I have wide A/T's on my truck.

I run 40psi also, and I've been adding a little more load for trips lately and taken to doing 42psi on the rears when loaded. Rides a bit smoother on the blacktop.
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by Lorgar » 13 Jun 2017, 11:33 am

franc wrote:Get a mate with another 4WD and head to the beach.

Take it in turns getting stuck so someone is free to pull out the other and try a range of pressures :thumbsup:


That's the way to do it.

I've done a fair bit of sand driving recently - which is new for me - and found it really is one of those things you need to get out and feel/do yourself to have any real understanding about it.

Wet vs dry, hard packed vs loose, and combinations of the above, all totally different/

Driving on firm, moist sand you can have road pressures and cruise along in high range at 90km/h hour like you're on the road without any drama at all.

I did a stretch of dunes where the sand was very light, bone dry, loosely packed, and with the surfance being constantly swept around by the wind.

I started out at 18psi with the centre diff-lock on, hit the first bit of sand as the road ended and instantly felt like I'd drove into a bog and sunk half a foot. :lol:

Aired down to 12psi, low range, cruised along fine at modest speed but every inch forward was this perpetual feeling of escaping the ground crumbling beneath me.

Turning is like steering a barge :lol:. Turn the wheel and after a few seconds the rig starts to gently bend in the direction prompted at about 1/4 the rate you turned the steering wheel :mrgreen:.

So yeah, saying "driving on sand" is a pretty meaningless term, really. You've got to hit a few different conditions to learn and know in advance for next time.

Going with a buddy vehicle is definitely ideal if possible. Came up on a 70 series on the soft stuff where he's just tried to power his way out of trouble, sunk into the chassis, 4 guys digging what looked like tunnels to China trying to get him out :lol:

(For the record I offered a snatch/winch but they said they had it under control :thumbsup:)
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by MalleeFarmer » 14 Jun 2017, 11:08 am

I live in the mallee and Deep Soft sand is what we have in abundance and I'm too lazy to drop pressure twice if I'm in trouble so usually just drop to 10psi

I've never had a tyre off the bead or a puncture from running too low. Also on the farm most of the time we run at 20-25 this is on anything from clay to sand and often it's a bit much in the sand so I always stick to lower than generally reccomended

My wife and I did a trip from mallee up to Darwin through the outback and once we hit the Oodnadatta track it was 20psi till we got out to bitty at Kulgera and back down to 20 once we got off-road again. Not a puncture or flat for 10000km

Bitumen: 36
Gravel roads: 20-25
Soft sand: 10-15
Firm sand tracks: 15-20
Mud: 15-20
Rocks: 15-20
Corrugated roads: 20-25
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Re: Tyre pressure for sand, mud, rock and corrugated roads

Post by BBJ » 15 Jun 2017, 3:40 pm

Die Judicii wrote:I actually ran so low once that two tires have come off the bead,, but it drove out.


What caused them to come off?

Cornering, hit a bank? Or just popped from lack of pressure?
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