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Thread: Sand Driving Tyre Pressures

  1. #21
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    I like these tyre pressure threads...............all the variations confirm an exact pressure is not necessarily something to obsess over so long as the pressure is within a range that is safe for the speed, load, distance travelled. Temperature is the biggest concern, if you can maintain a constant and correct belt temperature for the tyre you are using you have the correct pressure for the speed, load and distance.

    Pressures for sand, mud, rocks should be the highest you can use to achieve traction and the lower you go the slower you go, or you can reduce weight, which is not usually practical.

    I use (used to use, it just spat the dummy so the tyre dogs are back on)a rather expensive tyre pressure/temperature monitoring system and run 26 front and 28 rear (defender unloaded and Cooper ST maxx ) with a 2-3 psi increase at running temperature. Add a bit of weight and I might have to go to mid thirties or higher to maintain correct temperature. Most tyres are way, way over inflated for road use.

    Rick

  2. #22
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    Quote Originally Posted by bushrover View Post
    Most tyres are way, way over inflated for road use.
    Why do you say that Rick? I am not trying to be a smart-ass just interested in your views on this.
    At a defensive driving course I did almost 20 years ago they taught us that running on-road tyres at 35-40psi was better for several reasons:
    - flatter contact of tyre to road surface
    - better dispersion of water
    - more even tyre wear
    Maybe that was the case 20 years ago and is not any more due to changes/improvements in tyre design?

    I appreciate that high-20's gives a more comfortable ride than high 30's on the road.

    For my off-road jaunts, I rarely drop much below 20psi on 255/85R16 BFG KM2's (or previous Maxxis Bighorn 255/85R16) and have never had any real problems. I have been afraid to drop to sub 10psi in case I pop a bead on my 16" rims. Heartened to hear the 16" P38 rims are rated well in terms of non-bead-popping

    Cheers, Paul.
    My toys, projects and write-ups at PaulP38a.com

  3. #23
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    Quote Originally Posted by PaulP38a View Post
    Why do you say that Rick? I am not trying to be a smart-ass just interested in your views on this.
    At a defensive driving course I did almost 20 years ago they taught us that running on-road tyres at 35-40psi was better for several reasons:
    - flatter contact of tyre to road surface less road grip and can be dangerous if overinflated for conditions.
    - better dispersion of water as above, less road grip at high pressure, slow down to allow the tyre to disperse water. It is the tread pattern that disperses water, slow to a speed to let the tyre work.
    - more even tyre wear [COLOR="rgb(244, 164, 96)"]and much greater potential to do tyre damage. At the correct pressure for the weight and speed a tyre will wear evenly. Over inflation causes crown wear and centralised heat buildup at the crown[/COLOR].
    Maybe that was the case 20 years ago and is not any more due to changes/improvements in tyre design?

    I appreciate that high-20's gives a more comfortable ride than high 30's on the road. [COLOR="rgb(255, 140, 0)"][COLOR="rgb(244, 164, 96)"]I am not interested in comfort. Just tyre life and road grip[/COLOR].[/COLOR]

    For my off-road jaunts, I rarely drop much below 20psi on 255/85R16 BFG KM2's (or previous Maxxis Bighorn 255/85R16) and have never had any real problems. I have been afraid to drop to sub 10psi in case I pop a bead on my 16" rims. Heartened to hear the 16" P38 rims are rated well in terms of non-bead-popping [COLOR="rgb(244, 164, 96)"]I have dropped to 6psi to get out of trouble and re-inflated immediately after. Low low pressure equals low low speed. At 10psi you should be able to idle out of most situations in sand. Big revs digs holes and spits tyres, but looks impressive.[/COLOR]

    Cheers, Paul.
    I am no tyre expert, but in my last role my tyre and tyre management budget was around $15M so management was very interested in extending tyre life. Tyres pressures on the side wall are usually at maximum rated load and rated speed for that tyre type. For any particular trip, pressures should be adjusted to suit the changing travelling conditions. If you are on bitumen, I think the biggest advantage of increased pressures is fuel economy and less rolling resistance, but correct pressure is best and that is not the same as your mate in his vehicle or anyone's recommendation from their vehicle. Different tyres, different driving styles, different weight, different speed, distance to be travelled, road surface conditions all determine tyre pressure required. Pressures should be the lowest possible to be safe for the conditions. However, we all compromise.

    Rick

  4. #24
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    We were worried about popping a bead too, and pumped them back to 20ish as soon as we were through. The back rim was about 2 inches off the ground.

    Ive always thought in a passenger constructed tire you can get away with lower pressures, but on an lt carcass you dont want much flex in it at all. Weve run 65 in the rear whilst towing and they were a lot cooler than at 40 which ive always thought had a direct bearing on tread life too - but who knows.

  5. #25
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    Quote Originally Posted by benji View Post
    Ive always gone 16psi front and back if im lightly loaded, and 18 if im loaded. 26 would be way to high.
    Agreed , that's what's I have used with 32 and 33" tyres on 16 inch factory rims

    Never popped a bead , but I have had grit and sand become trapped between the rim and the tyre causing a slow leak
    The pre set / adjustable tyre deflation valves can make life easier , recommend Staun Brand , and "no loss"valve caps

  6. #26
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    Quote Originally Posted by RoverMac View Post
    Agreed , that's what's I have used with 32 and 33" tyres on 16 inch factory rims

    Never popped a bead , but I have had grit and sand become trapped between the rim and the tyre causing a slow leak
    The pre set / adjustable tyre deflation valves can make life easier , recommend Staunch Brand , and "no loss"valve caps
    I also use the staunch presets, 16 up front and 18 in the rears on the 265/75/16's on the standard RR 16" rims.

    Gary

  7. #27
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    HI

    I started out with 16 all round but dropped it to 14 all round to help get out of a pretty gnarly spot.

    Steve

  8. #28
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    And you did well my son.
    Showed those D3-4s how to do it.
    Pity about the back bumper on your race down the dune to get to the climb out. But who needs plastic anyway.
    And we now know how good Evoques are in sand .NOT!!
    Regards Philip A

  9. #29
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    Quote Originally Posted by PhilipA View Post
    And you did well my son.
    Showed those D3-4s how to do it.
    Pity about the back bumper on your race down the dune to get to the climb out. But who needs plastic anyway.
    And we now know how good Evoques are in sand .NOT!!
    Regards Philip A
    Hi Phillip

    I think the main advantage the P38 had over the Disco was sheer brute force, the situation required momentum and the 4.6 V8 was able to accelerate faster than the diesel Disco so I hit the slope at a higher initial speed.

    Yeah the plastic fantastic bits are in my sights now, time for the Bauhaus approach

    Steve

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