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Cuppa
18th September 2017, 07:37 PM
Arrived in Birdsville today, camped out of town a bit, down along the river.

Left the Tvan at camp & went out to Big red/Little Red .... whichever - the first one you get to where the bitumen stops.

My first ever sand dune. "Probably not necessary" thought I, "but I'll let the tyres down just in case. Fronts down to 22psi & rears down to 27psi.

Drove up the dune heading away from Birdsville in second low with zero problems - easy peasy.

Down the other side equally easy, although noting that the sand was a lot softer, especially near the top.

I should mention that this was around 3.30pm on a hot sunny day. I knew that the loose/soft sand was looser/softer when hot, but reasoned to myself that we'd seen others coming back with their Simpson desert flags waving, & besides which anyone crossing the Simpson simply couldn't cross all the dunes in the early morning cool of the day.

Well I'm afraid coming back up was such that I was pleased there was no audience other than MrsTea. It took me 7 attempts & I was seriously considering the possibility we would not get back to camp tonight! I had expected to get up in 2nd or 3rd low. But quickly realised that I was going to need more momentum than this allowed. In the end I
got up in 2nd high, foot well down & giving it the berries, & me just a passenger, trying as best I could to stay in the existing wheel tracks. It got me up... just.....but I'm sure I recall reading of folk motoring up the sides of dunes at 2000rpm - taking it easy.

Are most dunes not all soft at the top like this one was, am I just a crap novice dune driver, or is crossing ones chest, yelling "BANZAI" & planting the right boot standard procedure?


http://www.nissanpatrol.com.au/forums/images/imported/2017/09/117.jpg

mudnut
18th September 2017, 07:47 PM
I usually run 18 psi front and rear but have had to let them down to 15 in real soft stuff. Just learn not to turn sharply. To get the optimum pressure for your set up and sand type, let the tyres down by increments. Drive forward to say 20-30 odd kmh and put the clutch in or in neutral for an auto. The vehicle should roll to a stop, not dig in. Make dead sure you go straight up or straight down a dune as it is very easy to turn turtle. As for the correct gear, my RB30 has a terrific rev range but bugger all low down grunt, so the diesel guys will have to guide you as to the best gear to climb a dune. I also like to walk up a difficult dune to check it out first.

Bigcol
18th September 2017, 07:48 PM
usually tyres down to 18 all around, and float up to the top........

that saying, Ive never driven Big Red, but works most other sand hills.

lowest I've ever had to drop them to get up a hill was 10...........

oh, and give it the berries on the 2nd attempt

Winnie
18th September 2017, 08:00 PM
I got up the hardest line on Big Red with 10 psi in my tyres. Tried a few times at 18 and wasn't having any luck.

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Plasnart
18th September 2017, 08:01 PM
Yep 18psi is your friend in sand cuppa. Have been down to 10psi but thats scary low so really only in emergency and only in a straight line or youll roll the bead. Havent done big red myself but have done many dunes, including some gnarly ones. I usually use low 2nd, hit it at 2000rpm and dont let it drop below that. The td42 as you know has heaps of grunt so 2000rpm to 3000rpm is your zone. Roadies and all terrains better in sand than muddies too.

Have another crack tomorrow at 18psi and you should notice a nice difference, plus your confidence will shoot up. Good luck mate.

Clunk
18th September 2017, 08:06 PM
Depends on how soft it is.... I usually start at 15 all round and work my way down if needed..... Lowest I've been to is 8

Cuppa
18th September 2017, 08:29 PM
Thanks fellas, I was worried about taking the rears down too low because of the weight we are carrying. Sounds like less air is the go. Plassy that's good advice about going back for another go tomorrow, just wish I hadn't added more weight when we got back to town (filled both fuel tanks plus the water tank). I'll probably wait until we get to more dunes elsewhere I think, especially as the road out to Big Red is in really horrible condition (just after the race weekend).

We're going across Walkers Crossing to Innaminka & then down to Camerons Corner so maybe we'll find more dunes somewhere down there?


Winnie - so when you went across the Simpson were you constantly airing down for dunes? What pressure/speed did you use between the dunes?

Winnie
18th September 2017, 08:35 PM
Thanks fellas, I was worried about taking the rears down too low because of the weight we are carrying. Sounds like less air is the go. Plassy that's good advice about going back for another go tomorrow, just wish I hadn't added more weight when we got back to town (filled both fuel tanks plus the water tank). I'll probably wait until we get to more dunes elsewhere I think, especially as the road out to Big Red is in really horrible condition (just after the race weekend).

We're going across Walkers Crossing to Innaminka & then down to Camerons Corner so maybe we'll find more dunes somewhere down there?


Winnie - so when you went across the Simpson were you constantly airing down for dunes? What pressure/speed did you use between the dunes?Nah mate I aired down to 18 at the start of the crossing and that's where it stayed until we hit big red. We had 0 dramas with dunes until big red, nothing compared to it.
Only 4 of us actually conquered the hardest line on Big Red and AB got so close it was heart breaking. We watched a few modern auto 4WDs with traction control and other driver aids drive up it with ease.

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Plasnart
18th September 2017, 08:50 PM
Nah mate I aired down to 18 at the start of the crossing and that's where it stayed until we hit big red. We had 0 dramas with dunes until big red, nothing compared to it.
Only 4 of us actually conquered the hardest line on Big Red and AB got so close it was heart breaking. We watched a few modern auto 4WDs with traction control and other driver aids drive up it with ease.

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Agree i also set and forget at 18psi. But I'm in a loaded wagon, youve got a pod plus ball weight on the rear so id maybe set rears at 20-22psi when towing through that country. This is only for low speed stuff, around 60kmh or so mate. In the wagon i wouldnt be concerned with 18psi until around 80kmh. Just my opinion.

gubigfish
18th September 2017, 09:06 PM
Tyre pressures and momentum are your key always back off when you get towards the top as you want to stop when you get to the top/crest and always drive straight down and don't try and turn

AB
18th September 2017, 09:08 PM
We watched a few modern auto 4WDs with traction control and other driver aids drive up it with ease.

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V8, traction control and auto, bloody cheaters hardly drove it lol. They did do it with ease though.





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GQtdauto
18th September 2017, 09:30 PM
Thanks fellas, I was worried about taking the rears down too low because of the weight we are carrying. Sounds like less air is the go. Plassy that's good advice about going back for another go tomorrow, just wish I hadn't added more weight when we got back to town (filled both fuel tanks plus the water tank). I'll probably wait until we get to more dunes elsewhere I think, especially as the road out to Big Red is in really horrible condition (just after the race weekend).

We're going across Walkers Crossing to Innaminka & then down to Camerons Corner so maybe we'll find more dunes somewhere down there?


Winnie - so when you went across the Simpson were you constantly airing down for dunes? What pressure/speed did you use between the dunes?

There is sand that way Cuppa but nothing like big red , when I was there I noticed similar to you easy easy getting over but long way down on soft sand , I had about 20 psi from memory in the muddies and got over big red but took the right hand line .
Grey nomads with cheese slices and highway pressures made it up and over , well most of them , getting back over little red for me was ok but the sand is very soft at the top of big and little red .
Seen video of 4bys pulling camper trailers up big red but no idea how they made it .

Old Wal
18th September 2017, 10:05 PM
All good advice. My wife and I did a West to East crossing of the desert at the end of July . I too was a novice ( my experience at that stage consisted of travelling Googs Track twice and going from Birdesville to Eyre Creek and back ). I found that 18 in the front and 24 in the rear tyres worked for me. Set tyre pressures on the Rigg road and didn't touch them until we came off Big Red ( I didn't take the hardest line up Big Red - too heavy ). My ute with my slide on camper and all our gear is heavy. I found that low third or 2nd was the best ( I have 43 % reduction gears fitted ) for us - crawled up at about 10-15 km/hr. Got it wrong a few times by using high first and then having to back off due to holes near the top of the dunes and running out of puff.Mines at GU 4.2Tdi leafy . Watched some bounce up dunes flat out with wheels off the ground at times which worked for them but wasn't the technique for me - worried about breaking something. As others have said have a try at different pressures and you will soon see what suits your setup. Every dune conquered builds your confidence.

MudRunnerTD
18th September 2017, 11:28 PM
When in doubt, let air out.

Tyre pressure. No wheel spin and momentum is the key.

I air down to 18psi all round in clay and mud. 22psi in the Vic High Country where there is plenty of grip and 15 is my starting number in the sand. Beach or Desert. 15 is a great spot.

B8g red I went down to 10 for the hard side but aired back to 15 for the run in to Birdsville.

TPC
19th September 2017, 08:37 AM
In the Prado I had I would go down to 22psi and got up Big Red no worries but that was petrol auto.
I have run 18psi on the Patrol in the sand, have not found the need to go below yet.

Hodge
19th September 2017, 09:16 AM
Bit of a side question . But would locker/s have much benefit up a sandy dune ?
I know it's a good chance there mightn't be any wheel lift .

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Rossco
19th September 2017, 09:21 AM
Bit of a side question . But would locker/s have much benefit up a sandy dune ?
I know it's a good chance there mightn't be any wheel lift .

Sent from my SM-G920I using TapatalkYeah they do actually probably more so than you would expect. Last time went up big red dropped down to 10 psi both lockers on, it didn't want to turn too well ! ! , but made it up pretty easy. Yep for big hills like big red momentum & power is key also being careful with gear changes in a manual, need to make sure to change early and not stuff or it can all come undone.

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pearcey
19th September 2017, 09:50 AM
Did the Canning with camper on all at tyres at 15,no probs, down there in the lower corner of WA I ran 10 all round and again no probs. On a couple of occasions home in SA I`ve been down to 5 but thats extreme but works, only got to be very carefull no harsh turns or driving over roots, stumps or rocky bits. I always use 2nd low or 3rd.
Safe travels mate, oh how good is Mrs Tea on the shovel LOL

Dr Gary
19th September 2017, 12:38 PM
We did Big Red middle line from West to East. 18 psi worked fine drove straight up. Low range 2nd and about 3,000 rpm in our 3.0 Di. Carried 120 kg extra fuel and water, all camp gear. AT tyres, no lift. We struck a problem earlier in the trip with 22 and 24 psi. I SHOULD have had front diff lock--max trax didn't work well with the open diff.

katwoman
19th September 2017, 01:16 PM
Gas injection worked for me [emoji2]


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the evil twin
19th September 2017, 01:24 PM
Diff locks can make the world of difference as it stops the front ploughing in.
Thats why one of the old school techniques is to reverse up the dune if you have LSD or rear locker and not front.

Tyre pressure will always be the best aid tho and it is an exponential thing.
Dropping, say, 3 PSI from 18 to 15 makes a bigger difference in footprint than dropping 6 PSI from 24 to 18

For disbelievers on 4WD courses I use a marker to show the difference in footprint between 24/18/15 and it is a bit of an eye opener.

Lower pressure on sand means less load on the engine, less fuel used and much less stress on the Driver.
You want to 'float' not 'plow'

For dunes I use Gods gear (2nd low in a manual) or 1st high and on occasion 3rd low if the approach and incline permit.
If you don't make it let the vehicle stall out
DO NOT punch the Clutch in a manual as the drive backlash from windup torque is enormous.
Do a stall recovery procedure, if you don't you significantly increase the odds of a Utube Moment.
When safely back at the bottom assess if a tad bit more momentum will get you over and Mach 3 is def not an option.
If a judicious bit of extra right boot for an extra couple of K's at the bottom won't help, start dropping tyre pressure.

TimE
19th September 2017, 01:31 PM
Big Red, 19 psi all round, 2nd low (pre 43% gear reduction and pre elockers), run up at 3,600 rpm, easy :)

Bulbous
19th September 2017, 02:51 PM
Yokohama A/T-S 285/75 R16 LT

Deflate to 12 PSI in Front tires, 10 PSI in rear tires. Have fun.
73224

paulyg
19th September 2017, 04:49 PM
When we did a west to east crossing of the Simpson Desert, it was quite dry, I started with 18psi, but it was hard going, dropped pressure down to 15psi front and 16psi rear and had no more problems. Sometimes it can be hard to tell what conditions are going to be like until you start driving, then adjust as needed.
Big Red I had 12psi front and 14psi rear.

MB
19th September 2017, 08:43 PM
Great question Cuppa and jealous as you're both out there amongst our great big land mate! Being a Mexican mountain man myself with a heavy ute too intrigues me this thread. Our weights in sand versus arse end safe/trouble free PSi must have some consideration I imagine. As ET kindly mentioned of student deflation footprint displays at varying PSi's I'm thinking heavy rigs versus tall tyres and safe rim sizes could matter too? Would be cool to have a rough guided percentage of footprint over tyre versus varying load PSi I guess, even sounds difficult typing that wacky theory, lol :-)

Avo
19th September 2017, 09:15 PM
psi guide for sand,dunno about the uphill bit but this is what i learnt..

you should be able to back off go pedal(cant spell excalorator) and come to a rolling stop....gentle as easy does it...down here when i see sand it's straight to 10psi and to be honest even other places i go for 12...the hard bit about hill climbs is there is usually a lip at the bottom or the top so speed sometimes doesn't or isn't always an option..down here unless its callcup we just gently and easy..as long as ya have revs on hand you usually have aenough tourque to deal with most of the sand and hills here

Cuppa
19th September 2017, 09:42 PM
Great question Cuppa and jealous as you're both out there amongst our great big land mate! Being a Mexican mountain man myself with a heavy ute too intrigues me this thread. Our weights in sand versus arse end safe/trouble free PSi must have some consideration I imagine. As ET kindly mentioned of student deflation footprint displays at varying PSi's I'm thinking heavy rigs versus tall tyres and safe rim sizes could matter too? Would be cool to have a rough guided percentage of footprint over tyre versus varying load PSi I guess, even sounds difficult typing that wacky theory, lol :-)

The weight of a laden ute does affect the footprint, & recommended pressures are, I suspect mainly for wagons & possibly less weight. Even for road/dirt road driving I am yet to pick perfect pressures. Since leaving home I have gradually reduced pressures from what I started out with. I know the 'rule of thumb' for pressures in LT tyres is a 6 psi increase from cold to hot, but have been unable to achieve this in the temperatures we've been driving in. Mainly I get a pressure increase of around 10 psi regardless of the cold pressure, we have been driving slow though. Rarely above 80kph & often less on bitumen, & 40 to 60 on dirt. 40 psi rear & 30psi front seems ok on dirt. (cold) 4 or 5 psi higher for long sretches of bitumen. Bridgestone D697's 16" 265's.

Have to be a bit careful not to create too much sidewall bulge on the sharp quartz gravel used in these parts, already have one cut sidewall - not punctured & still holding. Was lucky. Copper in Boulia reckoned not to deflate at all.

For dunes the concensus of 18 psi or less all round - I would tend to translate as 18 front & maybe 22 to 24 rear (as per Old Wal's post) for our touring ute depending upon how full our tanks
are. But 'reading the sand' & adjusting to achieve a 'rolling stop' seems like excellent advice. I certainly failed to achieve a rolling stop & as ET suggested it felt hard on the transmission. I'll try the front diff lock another time too.

Off to Innaminka & then the Coongie Lakes - I gather there are dunes to cross there, albeit not 'Simpson sized" so will get a chance to experiment further.

GQtdauto
19th September 2017, 09:54 PM
The weight of a laden ute does affect the footprint, & recommended pressures are, I suspect mainly for wagons & possibly less weight. Even for road/dirt road driving I am yet to pick perfect pressures. Since leaving home I have gradually reduced pressures from what I started out with. I know the 'rule of thumb' for pressures in LT tyres is a 6 psi increase from cold to hot, but have been unable to achieve this in the temperatures we've been driving in. Mainly I get a pressure increase of around 10 psi regardless of the cold pressure, we have been driving slow though. Rarely above 80kph & often less on bitumen, & 40 to 60 on dirt. 40 psi rear & 30psi front seems ok on dirt. (cold) 4 or 5 psi higher for long sretches of bitumen. Bridgestone D697's 16" 265's.

Have to be a bit careful not to create too much sidewall bulge on the sharp quartz gravel used in these parts, already have one cut sidewall - not punctured & still holding. Was lucky. Copper in Boulia reckoned not to deflate at all.

For dunes the concensus of 18 psi or less all round - I would tend to translate as 18 front & maybe 22 to 24 rear (as per Old Wal's post) for our touring ute depending upon how full our tanks
are. But 'reading the sand' & adjusting to achieve a 'rolling stop' seems like excellent advice. I certainly failed to achieve a rolling stop & as ET suggested it felt hard on the transmission. I'll try the front diff lock another time too.

Off to Innaminka & then the Coongie Lakes - I gather there are dunes to cross there, albeit not 'Simpson sized" so will get a chance to experiment further.

There is sand between you and Innamincka via walkers crossing but not much in dunes , funny what you say about tyre pressures of road and what the cop said , I was loaded up that much that I scraped the rear tyres on the guard if a hit a moderate bump but if on dirt would air down to about 22psi .
This would increase to about 26 as the tyre heated up , no sidewall damage at all and did some rocky tracks , only puncture I got was from crap on the ground at the Arkaroola camp site .
Opinions vary with tyre pressures on dirt and rocky tracks but I've found 22-26 to suit mine and gives me a softer ride .

happygu
19th September 2017, 10:10 PM
Cuppa,

Airing down is definitely the key. 18 PSI is my rule of thumb for sand and I used this all the way across the Simpson, and we were fully loaded with food, water for 4 and fuel to get from Birdsville to Alice. With our weight, we would have been well over the load capacity, and heavier than your ute

I drove the hardest line up Big Red in my 3 Litre, but dropped to 12 PSI on my first run just to be sure I would do it first go and we sailed up it whereas everyone else couldn't make it even with massive runs at it ...

I did notice however, that the NA 4.2 Patrol in our group and another we came across struggled the most out of all the vehicles, and ran out of puff way earlier than the Turbo'ed vehicles ... not sure if it was just lack of confidence, lack of driver skill, not letting the tyres down enough, or just the short power curve, but don't feel too bad about struggling a little

Mic

Mc4by
19th September 2017, 10:26 PM
I haven't done too many huge dunes but around here I have done Whitehills a few times. 18 psi and second low (auto) worked pretty good. I tried with the front lockers after I had them installed and it made a big difference.

the evil twin
20th September 2017, 11:45 AM
snip...
The weight of a laden ute does affect the footprint, & recommended pressures are, I suspect mainly for wagons & possibly less weight.


Yes and No... the issue is one of density of the medium over which you wish to travel

18 psi is 18 psi IE that is the pressure inside the tyre 'pushing' on the inside surface and the ground is pushing back with a similar pressure on the outside surface.
Yes there are other factors like sidewall stiffness etc but they are much less a factor so for the purposes of the discussion lets ignore them for the moment...

If the pressure is raised on the inside of the tyre it will 'push away' and decrease the amount of tyre surface in contact with the ground... if the pressure inside is lowered the tyre surface in contact with the ground will increase until the two forces get back in equilibrium.

Yes, the more you load a vehicle (wagon or ute, doesn't matter) the more tyre surface ends up in contact with the ground but the key is the pressure exerted per square inch has increased but the density of the sand has not so neither has its ability to support the extra pressure/weight.

The medium (sand in this case) has a certain density and will react pretty much similar to a fluid so is analogous to a boat in a way (except a boat cannot change its footpringt).
The more weight in a boat the further it sinks until equilibrium IE the deeper in the water it rides and the more power it takes to displace.

The 4WD reacts in a similar way in sand.
Lets assume the sand/mud/snow density etc will support a surface pressure of 18 psi before you sink to a point where your 4X no longer have sufficient power to proceed.
Then 18 psi is the max pressure you will be able to exert onto the surface and get through.
A tyre with say 24 psi will exert a higher surface pressure than can be supported and will bog down or mire.

Sorry for the ramble so a quick Summary maybe in order?
If two vehicles of different weight but similar power availability and drive fitted with identical tyres attempt to cross a surface the tyre pressure at which point they will succeed or fail depends on the ground pressure exerted and is independant of the actual mass of the vehicle.
If a 3 ton Patrol fails at say 24 psi but gets thru at 18 psi then a 15 ton truck will fail at 24 but get thru at 18 psi also (all other things being equal)

PeeBee
20th September 2017, 12:26 PM
If two vehicles of different weight but similar power availability and drive fitted with identical tyres attempt to cross a surface the tyre pressure at which point they will succeed or fail depends on the ground pressure exerted and is independant of the actual mass of the vehicle.
If a 3 ton Patrol fails at say 24 psi but gets thru at 18 psi then a 15 ton truck will fail at 24 but get thru at 18 psi also (all other things being equal)

ET, I am not sure you have this correct. Negating the internal pressure of the tyre, which in your example states the tyres and pressures are the same, if you raise the weight of the vehicle by 500% your unit pressure is raised on the sand also, ie if say the 3t vehicle running at 18psi, has at each wheel 100 sq inches of ground contact, so 400 sq inches across 4 wheels. 3000kg = 6600lbs/400=16.5lb/inch2 unit pressure. If the load carrying capacity of the sand is 18psi, then yes it would float across the top. Now, next vehicle, same tyres/pressure, 33000lbs/400= 82.5psi, hence it will sink if the load carry capacity of the ground is 18psi, this is assuming the actual footprint of both vehicles is the same. So mass/footprint = ground pressure, nothing to do with internal pressure.

What you need to achieve is a 'footprint pressure that is less than the resistive pressure of the ground'. What cannot be determined is what the footprint of the tyre would be at 18psi on a 3t v 15T vehicle and I think this is more the issue than the internal pressure. I admit that logically the tyres on the truck would bag out more than at 3T, at 18psi, but I think the principle lies in actual footprint pressure than internal pressure of the tyre.

In conclusion, if we put 20 tyres on the 15T truck the ground pressure would be equal to the 3T one, being 33000/2000inch2 = 16.5 psi ground pressure, assuming the footprint is the same. Does this make sense?

Touses
20th September 2017, 12:50 PM
My head is spinning! Ummm......sandshoes?

the evil twin
20th September 2017, 01:35 PM
snip...

So mass/footprint = ground pressure, nothing to do with internal pressure.

What you need to achieve is a 'footprint pressure that is less than the resistive pressure of the ground'. What cannot be determined is what the footprint of the tyre would be at 18psi on a 3t v 15T vehicle and I think this is more the issue than the internal pressure. I admit that logically the tyres on the truck would bag out more than at 3T, at 18psi, but I think the principle lies in actual footprint pressure than internal pressure of the tyre.

In conclusion, if we put 20 tyres on the 15T truck the ground pressure would be equal to the 3T one, being 33000/2000inch2 = 16.5 psi ground pressure, assuming the footprint is the same. Does this make sense?

We are saying the same thing pretty much but in different ways... except for the internal pressure bit.
Totally agree on footprint which is what I am referring to also but perhaps should have used different numbers

The internal pressure (excluding other factors prev mentioned, construction, compressability etc) has a direct relationship to the ground pressure.
Yes if you used the same tyres as the Patrol on the truck you would need more or the truck would still be sitting on the rims but adding more tyres
for the same footprint and the pressure (18 PSI) in each one to achieve the same ground pressure remains the same.

the evil twin
20th September 2017, 01:45 PM
My head is spinning! Ummm......sandshoes?

ROFL... nope, Snow shoes mate not sandshoes.

Try to cross snow drift in sandshoes you won't make it.
Put on snowshoes (lower ground pressure) you will
A skinny bloke can use smaller shoes than a fat bloke but as they exert the same ground pressure ( lets say 18 psi) they both make it.
If they swap snow shoes the skinny bloke will do it even easier but now the fat bloke won't make it even tho he is wearing snow shoes.

A tyre distributes weight mainly by air pressure rather than direct pressure therefore the air pressure in the tyre is related to the pressure seen by the ground.

Touses
20th September 2017, 02:04 PM
ROFL... nope, Snow shoes mate not sandshoes.

Try to cross snow drift in sandshoes you won't make it.
Put on snowshoes (lower ground pressure) you will
A skinny bloke can use smaller shoes than a fat bloke but as they exert the same ground pressure ( lets say 18 psi) they both make it.
If they swap snow shoes the skinny bloke will do it even easier but now the fat bloke won't make it even tho he is wearing snow shoes.

A tyre distributes weight mainly by air pressure rather than direct pressure therefore the air pressure in the tyre is related to the pressure seen by the ground.

Oh I'm so much the wiser now! Off to trade in the maxtrax for snowshoes!:icon_bonk:

the evil twin
20th September 2017, 02:09 PM
Oh I'm so much the wiser now! Off to trade in the maxtrax for snowshoes!:icon_bonk:

ROFLMAO... we don't get snow here (same as you) but keep the Maxies they'll still work... as much as I'd hate too i guess we'll need to ask the Vics or the Tassie Frozen Ones to be sure tho

Bulbous
20th September 2017, 03:10 PM
Think of driving on sand as requiring a triangle or trinity of parameters, and yes they are listed in order of importance :)

1. Flotation.
2. Momentum.
3. Power.

If all three are present, then your triangle is good and you'll get through.
If any one of them is missing, then it's still possible to drive on sand, but you're compensating for the missing parameter. Sooner or later something will change and you will lose the second parameter also. See below.
If two of them are missing, then it's inevitable that you will get stuck.

Earlier I mentioned having a couple of PSI more in the front tires than the rear - this is because the forces applied to the front (steering) wheels are greater than the rear wheels, so if any tire is going to pop off the rim it will be a front one. Hence the slightly greater pressure.

Cuppa
26th September 2017, 01:36 PM
In Tibooburra, first time we have reception since Birdsville. Did Walkers crossing track to Innamincka, up to Coongie Lakes, before coming south to Tibooburra via Old Strzelecki Track & Camerons Corner.

.............Anyway, whilst up at Coongie Lakes we had 41 degrees & a howling gale which did a pretty good job of 'fluffing up' the dunes there around the back of the lake, so I had a chance to experiment with tyre pressures. It's one thing being told lower pressures make all the difference, & another thing to experience it yourself. Tried initially without the Tvan hitched up. 18psi in the fronts & 24 psi in the rears. Purred over the dunes in 2nd or 3rd low doing between 1700 & 2000 rpm. Amazing, & as Plassy said earlier it has really helped to build confidence. Pulling the Tvan over the same dunes, with same pressures was almost as easy, generally requiring 1 gear lower.

On Walkers crossing track, once past the initial rocky gibber section & into the white sand I dropped the pressures by around 30% & had a ball driving what was a soft sand switchback for a couple of hundred kilometres.

Thanks all, especially ET for your insights.

Cuppa

GQtdauto
26th September 2017, 04:51 PM
In Tibooburra, first time we have reception since Birdsville. Did Walkers crossing track to Innamincka, up to Coongie Lakes, before coming south to Tibooburra via Old Strzelecki Track & Camerons Corner.

.............Anyway, whilst up at Coongie Lakes we had 41 degrees & a howling gale which did a pretty good job of 'fluffing up' the dunes there around the back of the lake, so I had a chance to experiment with tyre pressures. It's one thing being told lower pressures make all the difference, & another thing to experience it yourself. Tried initially without the Tvan hitched up. 18psi in the fronts & 24 psi in the rears. Purred over the dunes in 2nd or 3rd low doing between 1700 & 2000 rpm. Amazing, & as Plassy said earlier it has really helped to build confidence. Pulling the Tvan over the same dunes, with same pressures was almost as easy, generally requiring 1 gear lower.

On Walkers crossing track, once past the initial rocky gibber section & into the white sand I dropped the pressures by around 30% & had a ball driving what was a soft sand switchback for a couple of hundred kilometres.

Thanks all, especially ET for your insights.

Cuppa

Only trouble we had with that track coming from the opposite direction was the gate at the Birdsville track was bogged up badly but apart from that no issue and tyres were 24 all round .
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