[Tejas@perioimpl]

Originally Posted by DirtyDan

I am guessing that the water does not create more solid ground but instead, a little water initially lets the wheels at first spin free and gain greater rpm and then dig past the water into more tractable earth. The water allows greater initial rpm if used judiciously.

A Brand French champagne with between 12 and 34 percent Pinot Meunier grape ratio works much better than water, if used at the prescribed temperature of 8 degrees, shaken not stirred.

Water helps by loosening up the muck stuck in the wheels thereby they clean faster while spinning. The clean tyre will then get better bite.

[wanderhermit]

Originally Posted by DHABHAR.BEHRAM

Dear all - Off Roading Technique On Sand? First let me tell you a short story.

The Great Escape, Rajasthan, 2002 A couple of times he got stuck. He would calmly go forwards and backwards, "break the bacK" of the dune and continue as if nothing had happened.

Dear Behram Sir,
Please let me thank you for such an informative thread.

The above post is a gem and I have saved it in wordpad to read and re-read untill I am comfortable with the sand.

I have done some basic sand driving in river beds and Sum desert in Rajasthan. The techniques you have mentioned with definitely help me to hone my offroading skills.

I have understood floatation and deflating the tyre part pretty clearly.

And am not so clear about angle of approach. Also can you please elaborate the "breaking the back" of the dune part a little more. May be with help of a pic or diagram or a video maybe?

[r_nairtvm]

Originally Posted by DHABHAR.BEHRAM

Dear all - Off Roading Technique On Sand? First let me tell you a short story.


Tyre pressure - everyone knows that on sand you reduce tyre pressure. But to what level? He showed us that day. I was merrily running 30 psi (foolish of me, I knew but I wanted to see what would happen). A mere 100 meters off the tarmac, my vehicle got stuck. Then we started reducing the tyre pressure. He came and calmly stood next to us, watching us with a bemused expression on his face. Then he showed us the masterpiece of sand dune offroading. He took my right hand as if a father would guide a child, slowly rolled my fingers into a fist and told me to hit the tyre sidewall hard with the area next to my little finger. I hit hard and got hurt. He told me to keep on reducing the tyre pressure and keep on hitting with the same intensity till the hurt level reduces, means that the tyre will deform on hitting, means that the pressure is less. But till how long? You can't deflate completely. He knowingly nodded his head and told us "till you hear a "dhummm dhummm" sould from the tyre. We followed his advice and we were pleasently surprised to hear the noise change from "phut phut" to "dhumm dhumm". He also told us to look at the tyre / wheel rim interface. "You should see the tyre deflect very slightly off and then come back on the wheel rim again, at the point where you hit". So we did this to 4 tyres. It took us half an hour to complete this exercise. He told us that it would take half an hour. After the OTR, I measured the tyre pressure. It was between 13 / 15 psi. The vehicle misbehaved totally on tarmac so it was essential to restore the tyre pressure at a petrol pump but on sand it was pure nirvana.
Behram Dhabhar

Behramji,

As I am based in Dubai, most of the OTRs hereabout are on Sand.

As a thumb rule - we reduce the pressure by about 50 to 60% of the original inflation pressure.

I believe on 4x4s usullay the inflation is aroung 30 psi +/- 3. so when we take off air on the above range it will leave us with a presuure of around 12-15.

I am amzed that the Rajastani Dunes experts "hitting method" also gives the smae end product. For us who practice deflating often enough we can feel the right presuure approaching by the changing shape of the tyre profile

I think the temperature of the sand also plays a key role here. The colder the sand (as in early morning and in winter months) it is more denser and can support about 15 + psi and when hotter we will have to go to <15 psi range. Often we start out with about 15 and then go down

I am re-posting here a few pictures of a friend of mine comming down a slope where the sand was very hot (there was a small snad avlance on that dune already if you notice) and he is using an abosolutely verical descent. This shows clearly what you were saying elsewhere never to descent slopes cross-wise.

We had come down the same route and was waiting our sweep to come down. That day we had just finished manning the TCP 01 of Abu Dhabi desert Challange (part of World Off-Road Rally Championships of FIA). You can see our vehicles and a lot of tyre ruts. We were returning to base camp in the opposite direction of the Rally route and hence the tyre tracks.

Best Regards & Drive/Ride Safe

Ram

[r_nairtvm]

Originally Posted by Sudarshan

Hi all , after going through all the discussions ,I found so much little about tyre pressure issue, I feel this aspect is almost ignored. ( except Behramjee, who has given some very interesting & usefull information )
Now can anyone shade some light regarding the following.
1) what is the safe limit to deflate a tyre ? is it 15 or 20 or 25 psi ?
2) Is there any standard about safely deflating a tyre ? & how long & on what surfaces it should not be run under low pressure ?
3) Are there any norms as per terrain ?(for example sand = 15 psi, Mud 25 psi ,Rocky dry =25 psi like wise.)

Sudarshan,

Have a look at the youtube video link below:

YouTube - Tyre Pressures and off road vehicles

It gives ome useful info on tyre pressures (at the end of narration there are some info slides) iin particular and also on off road driving.

Also below is a Landy specific link

http://www.landrover.com/gb/en/lr/ow...o-off-roading/

Best Regards & Drive/Ride Safe

Ram

[Sudarshan]

Hello Ram , watched the film a good one thanks. I am up to working up on something in this Issue .will post it later when I will reach conclusion . Its about the footprint of tyres in relation to pressure.

recently I worked up on and had experimented with it in the 'extreme offroaders OTR at 15 August .

I went up to 20% of the track with normal pressure & reduced it by 15% almost ( 35 to 30 & 28 to 25 Psi app.) it gave adiquate results . driving ease was felt notably .The terrain was mud/rock/slush

Though managed to get stuck while comming back (After Lunch, got lazy)

Thanks
Sudarshan

[rjstyles69]

Can somebody tell me what caused this Pajero to topple ?

YouTube - Mitsubishi Pajero off road crash

[headers]

I guess his approach to the edge should have been perpendicular to the edge.

One could have also averted the accident by turning into the direction of tilt when the tilt happens. But its an ACCIDENT

[sumannandy]

Hi Tanveer,

A quick question for you. Can you use 4wd low to climb hairpin bends and steep climbs for few hundred mtrs? I asked similar questions earlier and the response was yes for straight roads for few mtrs.

An ooty drive is planned. Last time my car had real problem in climbing some of the hairpins, well, I was not that experienced in Safari either. Planning to use 4L if that is okay.

Thanks in advance.

[tsk1979]

Nope, not on a turn. If its a dirt road then its okay, but on tarmac even a few meters can cause damage

[sumannandy]

Thanks Tanveer.

Then what is the way out for a steep climb or a hairpin? Half clutch?

Half clutch may not be helpful sometimes. As I had posted earlier, there was steep slope followed by a turn in a parking lot which resulted in clutch burn. I had to come back, shift to 4L, and then it was a piece of cake. I guess it cleared it without touching the accelerator.

I am trying to learn the best way. Thanks in advance.

[suman]

I don't think a few metres is going to cause any damage but that's just my opinion. Prolonged usage (of 4H) on long stretches of tarmac roads may cause what is known as "winding" but not for very short stretches.

I've used 4H climbing Rohtang (coming from Keylong) at a few places on the hairpins where the road was a mess. And 4L for a coupe of really nasty patches. Technically one may argue that it wasn't black top tarmac but it was potholed tarmac.

And I've used 4H going up the (steep) slope from Kasauli bus stand to the town. No issues.

[vardhan.harsh]

A quick question while we are discussing the 4H/4L modes on the safari. I use 4L mode in very stick situations where it would be really helpful and exclusively on non-tarmacs only. 4H too i use for mostly on non-tarmac (95%) of the time. However, i use 4H mode on tarmacs on extreme inclines where it could help in avoiding usage of the clutch. Also i use 4H mode for prolonged stretches (30km - 40km) on non-tarmacs. For e.g the road from Gramphoo - Batal recently, which has no tarmac laid. This though is not necessary, but i really feel comfortable in the 4H mode, since it provides that extra traction.

Questions:
1. Is it ok to use 4H mode for longer stretches (non-tarmac)?
2. Is it ok to use 4H mode for short very steep stretch (100m - 200m) or so.

i have not faced any issues so far using this strategy, but i would not know if it would hurt the vehicles in the longer run. Please advise.

[suman]

Originally Posted by vardhan.harsh

Questions:
1. Is it ok to use 4H mode for longer stretches (non-tarmac)?
2. Is it ok to use 4H mode for short very steep stretch (100m - 200m) or so.

IMHO -
1. 30-40 kms is quite a bit, particularly where there is no lack of traction as such. However, since it is non-tarmac, I do not think any damage is likely
2. I presume you are referring to tarmac here. Absolutely OK for short steep stretches.

[vardhan.harsh]

Originally Posted by suman

IMHO -
1. 30-40 kms is quite a bit, particularly where there is no lack of traction as such. However, since it is non-tarmac, I do not think any damage is likely
2. I presume you are referring to tarmac here. Absolutely OK for short steep stretches.

Thank you suman for the super quick response.
And yes i was talking about tarmac roads on short steep stretches.

[tsk1979]

How will 4H mode help in steep tarmac?
4L will help on steep tarmac as you will not need to half clutch as on some stretches, esp when reversing, in normal drive there is not enough torque.
in 4H, there is no change of gearing rations
1st gear in 4H is as tall as 1st gear on 2H.
So if you are on tarmac, you would need to use 4 wheel drive only if its rained etc., and you are getting wheel spin.
If the tarmac is so steep that the vehicle is tending to stall, and you need to half clutch, then you can use 4L which effectively gives you lower gearing.

Referring to question of harsh
1. 4H on dusty roads is fine, just do not cross 60kmph
2. Even in 2H mode do not cross 60 if you have not reversed the vehicle after disengaging 4WD, as the hubs are still engaged, and at speed there is chance of damage
3. For very steep slopes(tarmac) if 1st gear does not provide enough pull, use 4L for a very short distance(for example hairpins). After that try to maintain speed so that you never fall below 1500rpm in first gear
4. On Rohtang like climbs, the tarmac is severly broken. 4L can be used there as such terrain gives ample opportunity for slip. It will save your clutch as 8kmph on 1st gear 1000rpm may be too fast as you follow a slow moving truck. So instead of half clutching to proceed at lower spee, its always better to use 4L for a short distance, or if the grade is not steep and tarmac is good, fall back 4-5 car lengths.