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Old 11th July 2010, 07:09   #76
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Who said we're not participating?
Oh you are - Sweet sweat man!

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...till we reached a small town called "Jhunjhunu". After Jhunjhunu, we barely saw anything except
Jhunjhunu is a desert town and I remember passing through it in 1989 while going to BITS Pilani from DELHI!!

BTW, Sir, your techniques are educative and I hope to see you and your steed in action "our" side of the country!


Cheers
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Old 11th July 2010, 12:57   #77
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Originally Posted by DHABHAR.BEHRAM View Post
Dear all - as the currect discussions on off road driving techniques are proceeding mainly on "how to come down a slope", I would like to give my comments in totality.

Now if you interpolate our Jeeps within the spectrum of a similar brake system supplier, take a CJ3B / CJ340 with a 5.38 down a grade with "road Mu" able to hold its own (maybe tarmac to rubber, wet tarmac to rubber, certainly not dry sand), then you will observe that the vehicle is able to "crawl" down, or rather "clamber" down the slope in a very controlled fashion with no fuss in 4 wheel drive and in low ratio and in first gear.

There is your answer. Try and use as much "non-brake system" provided braking available in your Jeep to clamber down dslowly and safely.

The fun starts with vehicles having lower axle ratios, where even the maximum use of non-brake system provided also does not give effective deceleration to clamber down. Then the "road Mu" may not hold. Then the answer obviously is to get as much retardation as you can, means low range, means first gear and then make very very judicious use of the clutch pedal as a last resort to prevent the engine from stalling. Going down in neutral is a strict no-no. Whatever happens, never ever allow the vehicle to go sideways. To prevent the tilt, go as slowly as humanly possible. If the tilt starts, try and bring the vehicle to a halt. It is easier to bring a slowly moving vehicle to a halt. It may still not halt but steer into the tilt, correct the stance and then proceed, keeping the axis of the vehicle in the line of travel as possible.
Behram Dhabhar
I agree word by word. During my numereous interactions with DB he told me 5.38 with KMT 90 and 2.1 XDPon a 80 inch wheel base is a lethal combination.

The highlighted portion indicates what i exactly did when i approached the death slope. I was driving XD3p powered invader which is considerably heavier. My tail was sliding had to correct it to prevent roll over. I just wonder what we would have done if this was a long slope with a steep decent!

I was in 1 st low, 4.88 axle ratio, BA 10 gearbox, 15 inch wheels (close to Zero thread) and 1575 kg weight! I did tap brakes was i was sliding. Compared to me Robinson slid much better, may be due to complete reliance on brakes. Some times it works specially when it is a short and steep slope.

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Originally Posted by robinson.s View Post
Good to see quite a lot of discussion around the decline incident.

Let me add to it;

I definitely agree with engine breaking. But as we know, the crawling speed for a invader is high, so you got to rely on the breaks too.
I agree with you, it has to be a combination of both. There were times when you were too fast and close to roll over, I am not with you on those menevours. But other wise i like the way you experiment.


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Just thought I'd add one more off road technique in the light of some great discussions here...

Always try to ford against the stream diagonally cutting it. This way even if the currents are a bit strong you are allowing a relatively smaller surface area of your water fording vehicle to it. Smaller the surface area offered to the toward flowing water the lesser the impact/push it can have on the vehicle, which inturn might help one avoid being washed off. Simple technique, might save your day...

Beware of what is hydro-block and how it can destroy your internal combustion motor before lunging into the waters. Rest, let the common sense prevail.

If the vehicle gets washed off or falls sidewards or worst case turtles in the water, ensure you unbuckle your seat belt, quickly open the door and stay away from the vehicle if its tumbling through with the current, but, if the vehicle is not tumbling stay close to the vehicle climb and over it as fast as possible. Remember, your vehicle is your highest and the closest possible vantage point. Dont forget to stay clear of the hot exhaust pipes while climbing on top of a vehicle that has turtled

Wearing water proof gloves and high ankle boots is always recommended.

Behram Sir, that scorpio pull looks scary. What exactly is happening out there?

Wolf,
You seem to be a pro. Well done! Were you in AKC? Would like to see you driving in person. In theory you are spot on and very informative


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When you are rolling down a steep and slimy slope there is big chance the rear of your vehicle will step out. This is due to the momentum difference between the front and rear wheels. In low gears, the rpms the front wheels are rotating at is considerably lesser than the rear wheels. Though this is marginal its enough to get your rear wheels following a different track in comparison to the front hence the vehicle slides out. The other cause is ofcos the intertia difference between the front and the rear due to difference in traction levels. That is what I was trying to say in my previous post.
Can some one validate this?


Keep your expeience coming. Iam learning!
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Old 13th July 2010, 16:01   #78
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Wolf,
You seem to be a pro. Well done! Were you in AKC? Would like to see you driving in person. In theory you are spot on and very informative

Keep your expeience coming. Iam learning!
I am no where close to the word pro, you can safely trust me on that unhesitating. No, I couldn't make it to AKC, hopefully next time, I'd pray!

I would love to show you my driving skills, whatever little I own. I am glad you find my theories informative and appreciable, thank you for your positive acknowledgement.

@Behram sir: Your narration of the Rajasthan experience is beautiful. Very informative. The "phut phut" and "dhum dhum" technique was tested by my on Sunday, I was surprised to see it does work exactly as depicted below! I do have great respect for these folks who are the masters of their terrain. Reminds me of Man vs Wild thing on discovery...

Having said the above, I'd like to add a new Off road technique to the list;
*Never underestimate the damaging potential of a tree stump cut at cross section and left alone. Its a normal tendency to drive over rocks, trees, jetting foliage etc to save the low lying diff and gas tanks but normally a tree stump that has not been cut clean with a chain saw or tree saw can leave behind extremely sharp splinters standing tall like metal spikes. These splinters can puncture, shred or shear your tire comfortably. BEWARE, spot and avoid them whenever possible!

Last edited by The Wolf : 13th July 2010 at 16:16.
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Old 14th July 2010, 11:57   #79
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Originally Posted by The Wolf View Post
Having said the above, I'd like to add a new Off road technique to the list;
*Never underestimate the damaging potential of a tree stump cut at cross section and left alone. Its a normal tendency to drive over rocks, trees, jetting foliage etc to save the low lying diff and gas tanks but normally a tree stump that has not been cut clean with a chain saw or tree saw can leave behind extremely sharp splinters standing tall like metal spikes. These splinters can puncture, shred or shear your tire comfortably. BEWARE, spot and avoid them whenever possible!
Yes I saw santosh experiencing this at Avalkonda once. I dont know if he didnt spot the stump or deliberatly climbed over it . But he had a cut tyre and had to change it on the spot.

Santosh you can clarify if you are reading this.
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Old 14th July 2010, 15:39   #80
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^^ didnt spot, i was driving alone and the stump was on the left side (just going into a left turn), and had no spotter in the front. Next thing, I hear a crackle, and a looong hissss sound - game over. Side wall torn with 2 inches of tree still stuck inside the tyre.

Note - I was too noob back then and was running on 35Psi in a forest trail...!! Last week, I had to put my jeep over a similar sharp egde of a rock, but riding @ 20Psi let the tyre wrap around the rock like a glove and the rim was a few MM away from the stone, and I could pass it in peace...!! Talk about things you learn along the way..!!
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Old 15th July 2010, 14:32   #81
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But I am not sure about the direction to use in counter steering. I was sliding to the right, front wheels turning to the right, so which way I should turn the steering gently to counter the turn? BTW, gently is not very easy to do when things go haywire in a hurry.
The mistake many make is to turn too quickly and too far because they do not get immediate results. This can cause the rear end to snap around the other way really fast and can cause total loss of control. I can attest to this with a near fatal crash of my own many years ago caused by my over-correcting. When I finally came to rest, a power poll was staring at me through the windshield where the motor used to be. I used "engine breaking" to come to a stop (Okay, bad joke.)

Especially in 4 wheel drive, just a little steering wheel input is all you need. Many times the the vehicle will right itself before you even complete the input to the steering wheel.

Of course, the best thing to do is not put yourself into dangerous situations. It would be great if, as part of an event, drivers could practice skids and steering out of them on a safe large muddy field or some such place. Arka, work on it!

Steer out of a skid by steering in the direction of the skid....but use a light touch and stay cool.

Last edited by DirtyDan : 15th July 2010 at 14:35.
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Old 15th July 2010, 14:38   #82
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Dan, what you say applies during normal driving, we just need to give very slight twitch to effect the turn. In my case the steering had turned and locked to the right with the vehicle tilting to the left in a slope. So I turned it back to left as fast as possible in a non-PS steering wheel.
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Old 15th July 2010, 15:12   #83
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Dan, what you say applies during normal driving, we just need to give very slight twitch to effect the turn. In my case the steering had turned and locked to the right with the vehicle tilting to the left in a slope. So I turned it back to left as fast as possible in a non-PS steering wheel.
Well, it sounds like you did the right thing since you didn't flip over, crash etc.

I think there are too many variables to this situation to come up with a sure fired answer for every case.

Variables such as:


how steep?
danger of toppling
how much room at the bottom of the hill, left, center, right?

I have seen drivers descending, on the brink of toppling, turn in the direction of the topple and accelerate. The effect was to slam the side coming off the ground back down into the ground, but then you have to deal with the new direction you are travelling and the speed you have picked up.
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Old 16th July 2010, 08:12   #84
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Default Tyre pressure

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.)
There is one important referance here , though it may not be applicable to off road or soft surfaces & light weight vehicles . Few years back I did a refresher course of heavy vehicle driving at C I R T Pune. One of the expert/instructers told us about the bad & dangerous effects tyres have if they are driven at low pressure with load . It weakens the tyre & the damage is internal ( it cannot be assessed from outside) This is one of the main reason why tyres burst. Is this applicable to the LMV off road tyres?
Yours Sudarshan
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Old 17th July 2010, 10:45   #85
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Originally Posted by robinson.s View Post

But in general, I dont agree to the fact that, ABC is the only way you can take a decline. It completely depends on the Vehicle you drive the surface of the track and the angle you are in.


The best example what I can remember are those drivers who carry close to one tone of load in their 4x4 major and climb the hill without any modification in their vehicles. The only change they do is, add more leaf springs to take that weight.
Let me blatantly put it actoss, with our modified jeeps, we struggle to do that.

So I guess its all about how well you manuever your vehicle in every obstacles.
I couldn't agree with you more. A same descent and every vehicle tends to behave differently.

And some of these vehicles like mine run on rebelted tryes.
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Old 17th July 2010, 13:17   #86
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I couldn't agree with you more. A same descent and every vehicle tends to behave differently.

And some of these vehicles like mine run on rebelted tryes.

That's exactly the point am trying to drive to the forum. The off road techniques are generic, it can never be specific.

Nevertheless, its always better to know those techniques to improvise further or change as per your driving style.
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Old 19th July 2010, 14:04   #87
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Reviving this thread.
I have another question related to long wheelbase vehicles.
On some of the sections I do, many times the road if blocked due to landslide etc., and a make shift route is there where one has to get off the road.
Imagine such a section
/```````
The ```` is the road and the / is the slope downwards.
Going down is easier. Gravity does all your work, and you do not have to use momentum.

But coming up is a pain. If you come up fast enough, the front wheels will climb to the road, and the center part of the vehicle can hit the road, leading to damage.
On gentler slopes. I use 4L, slow down, and near the top start turning.

For example, front right wheel will be on the road, with front left just shy of the road.
Now gently in 4L I put front left on road, turn left fully, and start climbing. There is little wheelspin, but in the end I have rear left wheel in air, and rear right on the road and vehicle turning. I time it such that center of gravity is near the road part.

All this is very doable on not so slippery slopes and not so steep ones, but sometimes, that choice is not there.
Lack of power is not an issue. Safari can start from standstill in 4L even on 40 degree inclines. But lack of traction is an issue, so momentum is needed.

So how to long wheelbasers do this.
An example is here
EXAMM/AKC - A Passenger's report-p6254343.jpg

all vehicles here had short wheelbases, and as we know jeeps gypsies can take abuse, unlike a safari which is sort of a soft roader.

So in the picture you had above, imagine an adequately powered long softroader. Like safari/Pajero/Landcruiser etc. without any diff locks and around 200mm of GC.

what is the ideal technique.
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Old 19th July 2010, 14:18   #88
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Default Ramp-Over-Angle

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Originally Posted by tsk1979 View Post
Reviving this thread.
I have another question related to long wheelbase vehicles.
On some of the sections I do, many times the road if blocked due to landslide etc., and a make shift route is there where one has to get off the road.
Imagine such a section
/```````
The ```` is the road and the / is the slope downwards.
Going down is easier. Gravity does all your work, and you do not have to use momentum.

But coming up is a pain. If you come up fast enough, the front wheels will climb to the road, and the center part of the vehicle can hit the road, leading to damage.
On gentler slopes. I use 4L, slow down, and near the top start turning.

For example, front right wheel will be on the road, with front left just shy of the road.
Now gently in 4L I put front left on road, turn left fully, and start climbing. There is little wheelspin, but in the end I have rear left wheel in air, and rear right on the road and vehicle turning. I time it such that center of gravity is near the road part.

All this is very doable on not so slippery slopes and not so steep ones, but sometimes, that choice is not there.
Lack of power is not an issue. Safari can start from standstill in 4L even on 40 degree inclines. But lack of traction is an issue, so momentum is needed.

So how to long wheelbasers do this.
An example is here


all vehicles here had short wheelbases, and as we know jeeps gypsies can take abuse, unlike a safari which is sort of a soft roader.

So in the picture you had above, imagine an adequately powered long softroader. Like safari/Pajero/Landcruiser etc. without any diff locks and around 200mm of GC.

what is the ideal technique.
Hi TSK,

I faced the same question from a TLC owner, during TPC2007, when faced with 20+ Humps in a row.

The Trick is once the front wheels cross the climb, tap the accelerator, to hop/flick the vehicle very slightly across the edge to clear the Ramp Over Angle.

On a Inverted U-Shaped Hump the Idea is to get the Vehicle facing downwards after the climb, so even if the under-chassis is fouled or beached its easier, to drive out or recover with gravity on your side. and since most of the Under-Chassis components are aligned primarily for a forward movement.

Regards,

Arka
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Old 19th July 2010, 15:54   #89
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This thread can be a treasure trove is people contribute to it well. I wanted to know this and I know there will be many noobs who wants to know this.

What is the tyre pressures for various kinds of terrain. I know it can vary from vehicle to vehicle and driver to driver. But want to know a generic recommendation. This will help us noobs to atleast know if we need to deflate or inflate.

babu
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Old 19th July 2010, 15:59   #90
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Hi TSK,

I faced the same question from a TLC owner, during TPC2007, when faced with 20+ Humps in a row.

The Trick is once the front wheels cross the climb, tap the accelerator, to hop/flick the vehicle very slightly across the edge to clear the Ramp Over Angle.

On a Inverted U-Shaped Hump the Idea is to get the Vehicle facing downwards after the climb, so even if the under-chassis is fouled or beached its easier, to drive out or recover with gravity on your side. and since most of the Under-Chassis components are aligned primarily for a forward movement.

Regards,

Arka
Arka,

I think the success rate is comparatively less by taping the accelerator when your front wheels cross the climb.
As your front wheel losses complete traction in such inclines, and unless the vehicle has front dif locks, or the surface of the track has enough grip to give traction in all four wheels, will end up spinning wheels and burning the clutch.
To avoid spin on the edge of the incline or take the risk of hitting the cross member or skid plate, one should take it with the momentum and hop over the edge.

Can you give more insight on this. Really keen to know more, as its one of the most challenging obstacle in a trail.

Regards
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