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  #1  
Old 18 Sep 2006
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Sand ladders / tyre pressures

Hi,
I expect this has already been discussed here several times but I'm about to set off to Tunisia and Libya in a 300 Tdi, 130 Quadtec 4. I'm on BFG All Terrains, carrying a motorbike and some tools and stuff in the back.

1). would you take ali psp style sand ladders or waffle boards ? (I've never used either as all my desert driving has been on a motorbike !
2). what is lowest pressure you can run a BFG AT on in the sand ?

I've got a Viair on boad compressor with a 2.5gallon tank. It doesn't seem to be air tight - pressure drops over a few days. Does anybody have any tips on how to stop this ?

thanks,



Simon
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  #2  
Old 18 Sep 2006
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Theoretically you can go down to zero psi.
Try 14, try 12, etc. You just want a big fat foorprint.
Avoid tight turns at speed as you can roll the bead off.
Air back up after hitting the road and before high speeds.
A valve core tool makes airing down and up quicker.

Remove the fittings, re-install with teflon tape. If you have a blow-off/dump valve, there may be some junk in it. Remove, clean, etc if needed.
Spray soapy water on all fittings and check them as you would an inner tube.
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  #3  
Old 19 Sep 2006
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looking at your probablt all up weight I would say go for heavy duty waffle boards, you can get them on ebay for about 80 quid, I'm not sure ally ladders will be strong enough for you.
running at probably over 3 tons in landcruisers this year on continental sand tyres the lowest we had to air down to was about 20psi, and with the weight we were carrying they looked pretty damn flat at that. I would tend to air down 50%or so initially , then 5-10 psi steps after that if needed, you will quickly get a feel for what is right (once you get sick of digging!).
(we were fully inflated at 45 psi on the rears)
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  #4  
Old 19 Sep 2006
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Hi Simon, hows it going ?

Yep, as Moggy says it depends on the 130's weight with the tyre pressures - run the highest pressure you can get by with - this keeps the sidewalls cooler - drop a few psi at a time - I would avoid dropping so much that the tyre looks too flat - or as mentioned theres a good chance the bead will pop during a turn.
air up over any rock fields too - not just on asphalt - its easy to get lazy and rip out a sidewall - good as BFG's are, they havent got indestructible sidewalls and they will rip out over sharp stones.
a good routine to get into is to check the tyres cold every morning so you start the day with even flotation. (id start the day with 20psi in the dunes with the 90 and drop from there - again what works for the 130)
Go with the thick 50mm red (I think) waffle boards with the 130, they work a treat, you can also put some rope handles half way along the sides - which makes it easy to carry all 4 of them !!!
I got mine from Fibregrid - shop around though.

Have a good trip, say hi to Susan !!!
Cheers
Grif

ps I ended up selling the KTM and am now Married and living in Canada !!!
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Last edited by Gipper; 19 Sep 2006 at 05:52.
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  #5  
Old 19 Sep 2006
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I'm going to throw a spoke into the wheel about tyre pressures, back in the early 1980s I worked for Isuzu Trucks and had the job of demonstrating a 4x4 fire truck to the rural brigades in Australia.

The Japanese engineers wanted everything to be just right for the demos as there were about 500 trucks over 3 years. I was about to drop the tyre pressures for the sand demo when I was told in no uncertain terms to stop. The tyre engineers at Isuzu had spent a good deal of time testing pressures, rolling resistance, footprint of tyre, etc etc. There conclusion was that in sand (or snow) its the approach angle of the tyre over the sand that counts, having a wider, softer tyre decreased the approach angle and made it harder to drive forward. Having wider tyres was better but always operated at normal pressures for the weight of the vehicle.

Over the years I've always followed their mantra, and (I now live on an island made of sand) never been let down and have on numerous occasions ending up using my '58 Landy to pull out the $80k 'cruisers, Rangies and one Hummer, all with their tyre pressures dropped so low that they risked breaking the bead.
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  #6  
Old 19 Sep 2006
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Hi Roger,
Thats a spoke alright !!! - having bogged down in sand at road pressures a good few times I have to disagree - driving into a soft patch of sand with 35psi in the tyres (fairly wide BFG 265's) results in bogging down - the only way out is to air down (and dig)

As you have mentioned - airing down reduces the tyres approach angle - therefore giving LESS resistance than at road pressure - the tyre shape is no longer round - it is flattened at the bottom - as the tyre rotates it is constantly flexing to mould to the shape of the ground - have a think about that....

This combined with the improved flotation that dropping pressure creates - a longer footprint = reduced ground pressure= less chance of getting bogged.

Its not about having the widest tyre - its about having the tallest tyre you can run with your gearing - creating the longest (greatest area) footprint.

I would also say that short, wide 'Carlos Fandango' tyres at road pressures, create a lot of resistance in sand - a small footprint with a wide, steep approach angle.

Just My opinion

Your '58 Rover has got good gearing and its relatively light - so it will perform well in sand - is it an 88 or 107 ?

Cheers
Grif
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Old 19 Sep 2006
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Got to agree with gipper there. It can't be coincidence that when you get stuck at road presures if you air down you get out!!
in a suzuki sj413 I never had to air down, but it weighed about a 3rd of what we were running the cruisers at, which is probably about double what your 88 weighs!
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  #8  
Old 20 Sep 2006
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tyre pressures

I wouldn't advocate going below 16psi, it wont help the footprint much by going lower and you will possibly run the tyre off the rim.

Hint, attach 10' lengths of lightweight rope between the rear x member and the boards, that way when you get moving you can carry on till you reach safe ground...
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  #9  
Old 20 Sep 2006
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Its a shorty, non top, but I often drag a trailer along the beach as well, record so far is 10 kids plus me, plus trailer full of camping gear. Its got 750R16s on it with a tyre diameter of 800mm, whereas my Hilux has only got 700mm diamter tyres, which are wider but the Hilux always struggles in the soft sand in comparison to the Landy. The Hilux has never managed to tow a trailer onto the beach without some help to get it onto the hard sand near the waters edge.
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  #10  
Old 20 Sep 2006
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Smile

Quote:
Originally Posted by RogerM

The tyre engineers at Isuzu had spent a good deal of time testing pressures, rolling resistance, footprint of tyre, etc etc. There conclusion was that in sand (or snow) its the approach angle of the tyre over the sand that counts, having a wider, softer tyre decreased the approach angle and made it harder to drive forward. Having wider tyres was better but always operated at normal pressures for the weight of the vehicle.
Roger,

Do you know this saying:

"In theory, there is no difference between theory and practice. In practice, there is a big difference"
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  #11  
Old 22 Sep 2006
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thanks

Hi everybody,
And thanks for all the advice. Sounds like waffle boards would be good then. I need the quick because I'm going to Tunisia and Libya next week ! I'm in London - I think there is a place called Scorpion Racing that sells that up near the North Circular ?

I've got a Viair on board air system so inflating / deflating will be simple enough.

Shame you sold Susan's KTM Gipper ! home it has a good home. We use the 130 as a back up vehicle of long distance desert rallies - the bike in the back is a 450 KTM rally bike.

I've always found that reducing airpressure helps a huge amount. On a motorbike, using Michelin Desert tyres you can run almost empty of air and just about float over sand.

cheers,


Simon
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  #12  
Old 22 Sep 2006
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I'm sure Scorpion do them. If you run out of time, get some heavy duty rubber floormats (the ones threaded together) from a hardware place - work OK in a pinch. Unless you're overloaded, airing down will get you out 90% of the time.
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  #13  
Old 22 Sep 2006
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Hi Gipper

"driving into a soft patch of sand with 35psi in the tyres (fairly wide BFG 265's) results in bogging down - the only way out is to air down (and dig)"

Did you ever try those BFG 265/85's you were thinking about ?
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  #14  
Old 22 Sep 2006
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Just not necessary

Waffle boards/sand ladders are not necessary. Good compressor thus no hesitation in lowering to correct pressure is the key. I, nor anyone on my team has EVER needed sand ladders! Leave them behind and save cash and weight - you will, though, look slightly less cool at Sainsburys!

Lowering the pressure on strong sidewall tyres should barely affect the width - it's the footprint length increase that is key.

Roger M is not correct in his assertion that tyre pressure makes no difference -sorry! Never under-estimate driver (in)competence as a major factor in getting stuck.

On a final point, slow leakage from a compressor chamber cylinder is nothing new (see the one in your workshop that also needs to briefly top up after having been left for a while). Are you really in such a rush to re-inflate each time - perhaps CTIS is what you need (at about EUR2500 for a standard 4wd)?

Sam.
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  #15  
Old 23 Sep 2006
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If you plan on getting in some deep do-do , go ahead and mount a proper size winch.
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