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  1. #1
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    Default Tyre pressure in sand

    Look at the difference low tyre pressure make in sand. And don't you love that system with a coiled pipe from storage tube at each wheel for inflation / deflation?
    https://www.youtube.com/watch?v=BPwNVQqAiQY
    Mike Nieuwoudt
    '89 LR 110 V8

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  3. #2
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    Default Re: Tyre pressure in sand

    Next level in/deflate.
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    Louis Le Grange

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    Default Re: Tyre pressure in sand

    When driving in sand the objective is to get the largest "footprint" of your tyre, and if possible to achieve this on all four wheels. You will then have the maximum float on all wheels as well as no wind up on the drivetrain. Every vehicle is different due to make of tyres, weight of the vehicle on the said day.

    You can achieve this by doing the following. You will need 2 x steel rulers, a tape measure a tyre pressure gauge and 2 x A4 pieces of paper and a pen.

    Front tyre

    1 Start by parking the vehicle on a paved or level hard surface
    2 Place the 2x A4 paper one at the back of the right hand front tyre and the other at the front of the tyre
    3 Measure the distance between the paper as well as the height from the ground to the bottom of the rim.
    4 You will now have the footprint of the tyre at normal tyre pressure as well as the height of the tyre from ground to rim.
    5 Remove the paper and start reducing the air pressure say by ,2 of a bar and remeasure as above, keep doing this until the footprint stays the same. You will now have the maximum footprint of the front tyres, make a note of the pressure as well as the ground/rim height. Suggest you write it down for future reference. As the front tyre and axel will stay constant.

    Rear tyre

    1 Repeat the exercise as above, until maximum footprint has been achieved. You will notice that the rear tyre pressure will be different to the front tyres, this will be due to the said weight of the vehicle on the day depending on how the vehicle is loaded. Note the pressure and the ground and rim height for future reference.
    2 You now will have the correct pressure for the maximum tyre footprint for your vehicle for your sand driving on the day.
    3 You will have to repeat the exercise for the rear tyres on your trips day depending on the load the vehicle is carrying.

    Your vehicle should run lake a sand crab Maximum tyre footprint achieved and no windup on the drivetrain

    Another good tip is gearing.

    1 Drive your vehicle in first gear up to say 4000rpm in 4x4 high range, make a note of the speed on a piece of paper
    2 Repeat in every gear 1, 2 3 & 4
    3 Repeat the exercise in low range
    4 Now compare the speed between the gears, you can then select the easiest gear for sandy terrain for your vehicle

    Enjoy Feel free to pm me if you have any questions
    Neil Sauls

    2011 Isuzu KB 300LX 4x4 D/C

    VW Cross Up

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  6. #4
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    Default Re: Tyre pressure in sand

    Superb video, really like those pipe thingies,

    No man 4x2, diff lock, 4bar and drop the clutch my ou. My bakkie is te swaar gelaai vir daai pap bande
    Last edited by julius caesar; 2020/10/07 at 11:07 AM.
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  8. #5
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by NeilMac View Post
    When driving in sand the objective is to get the largest "footprint" of your tyre, and if possible to achieve this on all four wheels. You will then have the maximum float on all wheels as well as no wind up on the drivetrain. Every vehicle is different due to make of tyres, weight of the vehicle on the said day.

    You can achieve this by doing the following. You will need 2 x steel rulers, a tape measure a tyre pressure gauge and 2 x A4 pieces of paper and a pen.

    Front tyre

    1 Start by parking the vehicle on a paved or level hard surface
    2 Place the 2x A4 paper one at the back of the right hand front tyre and the other at the front of the tyre
    3 Measure the distance between the paper as well as the height from the ground to the bottom of the rim.
    4 You will now have the footprint of the tyre at normal tyre pressure as well as the height of the tyre from ground to rim.
    5 Remove the paper and start reducing the air pressure say by ,2 of a bar and remeasure as above, keep doing this until the footprint stays the same. You will now have the maximum footprint of the front tyres, make a note of the pressure as well as the ground/rim height. Suggest you write it down for future reference. As the front tyre and axel will stay constant.

    Rear tyre

    1 Repeat the exercise as above, until maximum footprint has been achieved. You will notice that the rear tyre pressure will be different to the front tyres, this will be due to the said weight of the vehicle on the day depending on how the vehicle is loaded. Note the pressure and the ground and rim height for future reference.
    2 You now will have the correct pressure for the maximum tyre footprint for your vehicle for your sand driving on the day.
    3 You will have to repeat the exercise for the rear tyres on your trips day depending on the load the vehicle is carrying.

    Your vehicle should run lake a sand crab Maximum tyre footprint achieved and no windup on the drivetrain

    Another good tip is gearing.

    1 Drive your vehicle in first gear up to say 4000rpm in 4x4 high range, make a note of the speed on a piece of paper
    2 Repeat in every gear 1, 2 3 & 4
    3 Repeat the exercise in low range
    4 Now compare the speed between the gears, you can then select the easiest gear for sandy terrain for your vehicle

    Enjoy Feel free to pm me if you have any questions
    Or you could simply deflate your tyres to 1 bar and give it a try, if we are talking dune sand. From there on simply play around a bit with the pressures and feel the result. 4x4 and sand driving is more about feel than bare numbers.
    Depending on your type of tyres, trying to push an A4 sheet of paper against the front and rear of the thread will be a bit of a hit and miss I would think, unless you drive racing slicks. But a decent MT tread pattern might make it a bit more difficult with large blocks and lugs.
    And what happens once you got your "maximum footprint" achieved and you drive around a bit, the tyre heats up, pressure builds up again and your maximum foot print is somewhere a few km behind you.
    Personally I'd rather spend time driving in sand then pushing paper...
    Last edited by HugoNotte; 2020/10/07 at 05:40 PM.
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  10. #6
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    Default Re: Tyre pressure in sand

    And there is backup when he gets stuck . Just offload the dozer for some help
    2011 FJ Cruiser
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by NeilMac View Post
    When driving in sand the objective is to get the largest "footprint" of your tyre, and if possible to achieve this on all four wheels. You will then have the maximum float on all wheels as well as no wind up on the drivetrain. Every vehicle is different due to make of tyres, weight of the vehicle on the said day.

    You can achieve this by doing the following. You will need 2 x steel rulers, a tape measure a tyre pressure gauge and 2 x A4 pieces of paper and a pen.

    Front tyre

    1 Start by parking the vehicle on a paved or level hard surface
    2 Place the 2x A4 paper one at the back of the right hand front tyre and the other at the front of the tyre
    3 Measure the distance between the paper as well as the height from the ground to the bottom of the rim.
    4 You will now have the footprint of the tyre at normal tyre pressure as well as the height of the tyre from ground to rim.
    5 Remove the paper and start reducing the air pressure say by ,2 of a bar and remeasure as above, keep doing this until the footprint stays the same. You will now have the maximum footprint of the front tyres, make a note of the pressure as well as the ground/rim height. Suggest you write it down for future reference. As the front tyre and axel will stay constant.

    Rear tyre

    1 Repeat the exercise as above, until maximum footprint has been achieved. You will notice that the rear tyre pressure will be different to the front tyres, this will be due to the said weight of the vehicle on the day depending on how the vehicle is loaded. Note the pressure and the ground and rim height for future reference.
    2 You now will have the correct pressure for the maximum tyre footprint for your vehicle for your sand driving on the day.
    3 You will have to repeat the exercise for the rear tyres on your trips day depending on the load the vehicle is carrying.

    Your vehicle should run lake a sand crab Maximum tyre footprint achieved and no windup on the drivetrain

    Another good tip is gearing.

    1 Drive your vehicle in first gear up to say 4000rpm in 4x4 high range, make a note of the speed on a piece of paper
    2 Repeat in every gear 1, 2 3 & 4
    3 Repeat the exercise in low range
    4 Now compare the speed between the gears, you can then select the easiest gear for sandy terrain for your vehicle

    Enjoy Feel free to pm me if you have any questions
    The Rocket science behind this will be a flat tyre at 0 Bar. The second best will be a tyre at 0.5bar.

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  13. #8
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    Post Re: Tyre pressure in sand

    Quote Originally Posted by Mike N View Post
    Look at the difference low tyre pressure make in sand. And don't you love that system with a coiled pipe from storage tube at each wheel for inflation / deflation?
    https://www.youtube.com/watch?v=BPwNVQqAiQY
    Thanks Mike this is what I am trying to tell the forum since joining in 2007. Best video I have seen thanks. You need to drop pressure on the trailer as well. But yes for some unknown reason people are afraid to deflate.
    Last edited by grips; 2020/10/07 at 09:24 PM.

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  15. #9
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by grips View Post
    But yes for some unknown reason people are afraid to deflate.
    too lazy to inflate, and of course the other word...ego...

    Have seen it time and again.

    One thing I have found interesting on a number of occasions. Take a group out, all driving their own cars. Call it training of you will.
    A nasty obstacle starting with a sandy climb, I stand at the bottom, stop each car individually and give instructions. At least 60% of the male participants will sukkel, tyres spinning and limiters bouncing and then stuck.

    90% of the female participants will make it, question is why? Because they listen and followed instructions because they don't have ego issues.

    Same in the dunes, manne kom ons stop en blaas bande aff. Nee vir wat my bakkie het 400kw en ek is nie lus vir tyd mors. And guess what happens next...
    Walter aka "Meerkat"
    slightly modded 02' 105 series 1FZ-FE
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    My heart beats to an African Bush drum...

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    Default Re: Tyre pressure in sand

    Quote Originally Posted by AboutAfrica View Post
    too lazy to inflate, and of course the other word...ego...

    Have seen it time and again.

    One thing I have found interesting on a number of occasions. Take a group out, all driving their own cars. Call it training of you will.
    A nasty obstacle starting with a sandy climb, I stand at the bottom, stop each car individually and give instructions. At least 60% of the male participants will sukkel, tyres spinning and limiters bouncing and then stuck.

    90% of the female participants will make it, question is why? Because they listen and followed instructions because they don't have ego issues.

    Same in the dunes, manne kom ons stop en blaas bande aff. Nee vir wat my bakkie het 400kw en ek is nie lus vir tyd mors. And guess what happens next...
    So true. But then I have gave up on tyre pressure and sand driving threads.

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  19. #11
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by grips View Post
    Thanks Mike this is what I am trying to tell the forum since joining in 2007. Best video I have seen thanks. You need to drop pressure on the trailer as well. But yes for some unknown reason people are afraid to deflate.
    I think the problem is a lot of people don't carry a compressor? Mine was stolen at Sodwana from the back of my bakkie after paying R100 to "park on the beach."

    I usually run my Amarok on 1.8-1.9 Bar and by the time I hit Dbn I am at 1.7ish which is fine for the beach in Dbn, and there is a garage just down the road if I do need to inflate. If you try that in Sodwana you will sink as soon as you hit the beach (I know) and you need to be closer to 0.5-0.7 bar.

    I learnt on this forum the importance of the trailer as well. Stupid not to think of this, but I had always just dragged the trailer through the sand but with a bigger boat I am now very aware of dropping trailer pressures as well.

    Beaches are like boat ramps. There are always people waiting around for the poephoel to come and provide some amusement and you don't want to be "that guy." As you say, always better to drop the pressures early and make sure you have a compressor. In sodwana I just drop the pressures the when we arrive and leave them soft until we head home, but I am very careful to drive very slowly and take corners very gently with the tyres that soft.

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  21. #12
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    Default Re: Tyre pressure in sand

    doesn't the Russian Tatra trucks (possibly others) have in cab tire deflator / inflators?
    My Life Loving It


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    Default Re: Tyre pressure in sand

    Many Russian military trucks have in-cab tire deflation/inflation systems. Typically they have very visible external pipework which looks pretty vulnerable.

    Quite a few American military vehicles also have in-cab tire management (including the Humvee), but much more neatly done. It is also available on the modern Unimogs as a factory option. It is quite easy to do if you have portal axles.

    I am actually surprised that those MAN's don't.
    Last edited by Peter Connan; 2020/10/10 at 05:34 PM.
    Beat-up rat rod of a '96 Nissan Patrol that bears the evidence of many wonderful adventures (and a few stupid indiscretions).

  23. #14
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    Default Re: Tyre pressure in sand

    The MAN does not have portals but planetary hub reduction, then its always difficult.
    Mike Nieuwoudt
    '89 LR 110 V8

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    Default Re: Tyre pressure in sand

    Quote Originally Posted by Peter Connan View Post
    Many Russian military trucks have in-cab tire deflation/inflation systems. Typically they have very visible external pipework which looks pretty vulnerable.

    Quite a few American military vehicles also have in-cab tire management (including the Humvee), but much more neatly done. It is also available on the modern Unimogs as a factory option. It is quite easy to do if you have portal axles.

    I am actually surprised that those MAN's don't.
    The Unimog had tyre pressure adjustment system since the 1990s. Many milityary trucks got that feature, it is even available from MAN:https://www.oemoffhighway.com/electr...m-13290-4x4-bb
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by grips View Post
    Thanks Mike this is what I am trying to tell the forum since joining in 2007. Best video I have seen thanks. You need to drop pressure on the trailer as well. But yes for some unknown reason people are afraid to deflate.

    How many times have I come across people stuck in the sand? In nearly all cases I have been assured that they have deflated their tyres.
    When I check the pressures they have usually been deflated to 2 bars!! What is it about air pressure? Price of air?
    As I spend 50% of my off-road time in the sand [work and play] my rule of thumb is 1 bar on vehicle and trailer. If I feel its not enough 0.8 bar is next.
    On the boat trailer its 0.5 bar from day 1 until we go home. 20 minutes with my built in compressor to inflate on departure morning.
    Last edited by Dave Hill; 2020/10/12 at 07:18 AM.

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  27. #17
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by Mike N View Post
    Look at the difference low tyre pressure make in sand. And don't you love that system with a coiled pipe from storage tube at each wheel for inflation / deflation?
    https://www.youtube.com/watch?v=BPwNVQqAiQY
    I took a coach across the Andes (Chile to Argentina) years ago. The coaches and many of the trucks on the route (hundreds of switchbacks) had the ability to add/reduce pressure in the tyres on the fly. The rig is a thin rod carrying a tube that runs into a connection concentric to the hub (so it doesn't twist). Not sure how it would work in sand. Apparently this is to allow for the change in pressure when driving from sea level to the pass @ 3800M
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  29. #18
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    Default Re: Tyre pressure in sand

    Quote Originally Posted by CanAmSteve View Post
    I took a coach across the Andes (Chile to Argentina) years ago. The coaches and many of the trucks on the route (hundreds of switchbacks) had the ability to add/reduce pressure in the tyres on the fly. The rig is a thin rod carrying a tube that runs into a connection concentric to the hub (so it doesn't twist). Not sure how it would work in sand. Apparently this is to allow for the change in pressure when driving from sea level to the pass @ 3800M
    Will not work in ZA - no anti theft device to prevent mischief. Once you stop, that device will be relocated
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    Default Re: Tyre pressure in sand

    Reducing tyre pressure has almost nothing to do with size of footprint but everything to do with the profile of the footprint.

    A hard tyre is like rolling a beer bottle across the sand - it pushes a hill of sand ahead of it, which it must then climb over. Press down on the bottle and it pushes sand away on both sides of the curve.

    A soft tyre is like a plastic bag filled with water, it rolls across the sand without making any kind of impression.

    When a tyre is at the right pressure the usual convex-ness where it touches the earth reverses into concave-ness, an ever-advancing inverted cup that rolls forward without disturbing the sand's surface or pushing it ahead, behind or sideways.

    The footprint area barely increases at all with deflation, and doesn't need to.

    (And the heavier the vehicle is loaded the better it works.)

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  32. #20
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    Default Re: Tyre pressure in sand

    I usually ask the guy if I can drive it out before starting to deflate. Deflating is PT. If that fails, well deflating helps...

    The important thing is to keep traction, and momentum. Spinning wheels have very little traction.
    For sand driving in principle , if you see spinning marks in your tracks deflate a bit more to improve traction, and floatation.
    Johan Kriel

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