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Discussion Starter #1
A while back there was a discussion about adding an ABS cutout switch in which a couple of the board members - one in particular - got all huffy and uptight about how the wonderful 39channellbellsandwhistles Wabco ABS (most advanced in its time) should never be disabled - even for extreme off-roading. And, while others presented all the right arguments on why this was not the case, nobody had an external reference to back up what was being said. I saw this today and had to think of that thread: http://www.4x4abc.com/4WD101/ABS_offroad.html. Just thought I'd pass the info along as general info (plus the site is kinda neat - good info for people starting to 4-wheel).



Why ABS could be bad for you when off-road


ABS was designed to keep wheels from locking up. ABS was designed to make driving safer (in most circumstances).

Locked up wheels can no longer steer the vehicle. For example, you would not be able to steer around an obstacle with locked wheels - with wheels locked you would slide straight into it. So, even though you are able to turn your steering wheel - the vehicle can not follow this command when the weels are not rotating. ABS keeps wheels rotating.

Again, ABS makes driving safer.

Not so on a dirt road!

Sand and gravel under the tires act like tiny ball bearings when you step on the brakes. As a result there will be very little friction/traction between tires and ground.

Therefore all four wheels want to lock up immediately.

ABS would keep them from doing so.

So you keep rolling and rolling, and rolling, and rolling. You might be rolling for too long and your stopping distance is going to be that of a container ship. Too long to be safe. You might even drive off a cliff.


Here is what you get with ABS off: When you hit the brake good and hard the wheels will lock up - the tires will immediately begin to dig in pushing against sand and gravel - this builds little berms in front of each tire, which very effectively slows down the vehicle. As you see, on dirt locking wheels can be good for you! Picture a cartoon horse stemming all 4 into the dirt after a fast run.

In fact, stopping without ABS on sand or gravel can be so brutal that you better have your seatbelt on - otherwise you will end up with your face in the steering wheel. Been there.

To deal with the negative effects of ABS on dirt, some manufacturers had installed a kill switch for ABS in their full time four wheel drive vehicles (for example early 90's Mercedes-Benz G-Class) but recent changes in the law prevents them from providing this option any longer. Seasoned four wheelers have either installed their own kill switch or simply pull the ABS fuse before hitting long stretches of dirt road.

Vehicles with part time 4WD don't really have a problem with ABS - ABS does not work in combination with part time 4WD anyway.
Also, on some vehicles you have an option of using full time 4WD/AWD or part time 4WD. Its up to you to chose the right setting.

More examples

By the way:
Aside from ensuring that you can steer your vehicle even under heavy braking ABS will keep your vehicle from fishtailing.
 

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2010-2012 Range Rover MkIII / L322
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Well that horse is certainly flogged. :lol:

I'd say the only reason to remove it would be to make the system more reliable - simply by removing it altogether it won't break or be a problem. I guess that's why people rip out the EAS as well, but then you've got to ask the question, 'Why am I taking this car and ripping out its guts to improve it?' I think that's where the a 1970's Classic comes in or a Defender if you need an oil burner up front. The P38 isn't a hard core off-road vehicle.

Does it really matter though (please refer to JS's picture)? Once you've got a tall 2 tonne vehicle out of control on the rough at speed, ABS or no ABS isn't going to matter. :pray:
 

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1995-2002 Range Rover P38A
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I can see the point, none the less on dirt roads if you had to break hard and turn the steering on none ABS the chances are you would flip, ABS installed its a different scene altogerther.

With 2.7 tons on the P38 ABS works well though maybe not so on lighter rice burners
I stand to be corrected here but on the P38 ABS only kicks in at 25kph or it it 15 not to sure
 

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I'll have to look at the system operation description , but in most 4WD, AWD vehicles ABS is automatically disabled when low range is selected.
I love all the panic and unwarranted fear on this board :roll:
 

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Discussion Starter #6
Rich998a said:
I'd say the only reason to remove it would be to make the system more reliable
I think that's where the a 1970's Classic comes in or a Defender if you need an oil burner up front. The P38 isn't a hard core off-road vehicle.
It's def not about removing the ABS (which I am happy to have as a copilot 99.9% of the time), just being able to shut it off in certain circumstances. The situation that the original poster (an Ozzie IIRC) was referring to was descending longer steep inclines off road. I've been in this situation as well - luckily on a shorter incline with lots of runout room. Slush/mud mix that I know I could have done a much better job on with locked wheels. And descending quickly ( less than 20mph - not fast) with no reaction to brakes is unnerving.

I've got an oil burner in my P38. :dance: And the whole reason for suspension mods (my setup is similar to Jsmooth's), skid plates, the winch bumper I'm working on, etc. is to make it even more capable off road while retaining (most of) the RR's on road feel for long distances. And a P38 can be a very capable off-road vehicle.

viperover said:
I stand to be corrected here but on the P38 ABS only kicks in at 25kph or it it 15 not to sure
Don't know exactly how fast (because I was concentrating on pooping my pants), but I've been slow enough to be able to think long and hard about what I'm going to do... :shock:

Funny, I was looking for info on this in the Owners Handbook section of the Rave and I couldn't find anything on low speed ABS - I did find this (which I've never read before) though :lol: :

• On soft surfaces such as powdery snow,
sand or gravel, and also on very rough
surfaces, braking distances with ABS may
be greater than those achievable with a
non-ABS system. This is because the
natural action of locked wheels on soft
surfaces is to build up a wedge of material
in front of the wheels which assists in
stopping (however, ABS will continue to
provide better stability and steering
control).

I guess the reference above was unnecessary...

Have there been any advances in figuring out a way to shut the ABS off w/o creating error messages?
 

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What an Eye opening post. On a recent trip on dirt roads with extreme washboard I noticed that the brakes were completely ineffective. I was putting the peddle to the floor and hardly slowing down at all. I figured it was because the truck was bouncing off the washboarded road but now it seems it might have been the ABS. BTW I was in high range and in all likely hood doing at least 40 MPH. (fun but a little scary). After a few turns I could get the truck to slow and eventually stop but it was a little bit sketchy.
 

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viperover said:
I can see the point, none the less on dirt roads if you had to break hard and turn the steering on none ABS the chances are you would flip, ABS installed its a different scene altogerther.
With 2.7 tons on the P38 ABS works well though maybe not so on lighter rice burners
I stand to be corrected here but on the P38 ABS only kicks in at 25kph or it it 15 not to sure
I wish ABS was disabled when you went into low ratio.
I've gone down hills at a slow crawl and ABS still kicks in.

ABS is LESS safe in certain circumstances and I would like to be able to disable it when in those circumstances.
My examples are towing down steep gravel hills at low speed say 15kmh or less. With ABS it takes forever to stop. When I have had ABS disabled in those situations my car stops promptly and nicely.

This thread might be flogging a dead horse - I doubt the people that jumped in before and said ABS is wonderful all the time no matter what will learn this time either.

Here are photographs of a real example.
[attachment=1:1h5m6wwh]rangie1.jpg[/attachment:1h5m6wwh]
This first photo shows me towing my old boat up the hill. The ABS issue is when going down and then around the next two corners as shown in the next photo.
Note the horizon is not level in the above photo but I don't have the software to fix it. The hill is actually steeper than it looks you can see how when looking at the house roof which is actually level
[attachment=0:1h5m6wwh]rangie2.JPG[/attachment:1h5m6wwh]

Anyway, it doesn't really matter that some people don't see why ABS disabling is desirable to us 1% of people that do more extreme stuff. I am able to drive it as it is, but the first few times would have been much safer without ABS.

I'm not motivated enough to work out how to disable it. Only that I know, in my car a faulty brake pedal (brake light) switch disabled my ABS but left my traction control working. It was great except for the dash warning and I think the brake lights may not have worked (not sure as the switch has a failsafe so maybe they did).

Greg
 

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Discussion Starter #12
ghind said:
This thread might be flogging a dead horse - I doubt the people that jumped in before and said ABS is wonderful all the time no matter what will learn this time either.
NFK - no kidding.

ghind said:
Anyway, it doesn't really matter that some people don't see why ABS disabling is desirable to us 1% of people that do more extreme stuff.
Very well put. It seems to me that there are some very opinionated people on this board. While going through some of the ABS threads to see where we are in terms of a cutout switch I found the following:
- people who want to incapacitate the ABS can't drive
- above people are stupid because the Wabco ABS is superb, great, state of the etc.
- above people should just rip out the EAS, ABS whatever and get over it
- above people are too extreme
- and new to this thread, above people are paranoid (thanks Jim :roll: )

Just to explain myself a little so maybe people will have some more understanding: I originally thought RR's were pieces of crap (mainly because I'd worked on the electrics in a number of RRC's - especially the early 3-fuse models) and had my heart set on a MB G-Wagen which I'd driven both on and off-road. A bunch of yrs ago, pop-in-law loaned me and my now wife his RRC for a trip to the south of France. We did about 2400km's on road and some mild off-roading in the Luberon and on the beaches of the Camargue and I was hooked. A G-Wagen is quite capable off-road but not so much fun on the highway. Neither is a Defender. A RR is just as capable off-road and as comfortable as any luxury car on. This lead to my purchasing a RRC (in pieces because I was still in law school and broke) which lead to a second RRC and then to my P38 and an LM.

We have the P38 set up as our travel/off-road vehicle with 2 rooftop tents, suspension mods, etc. We do both long stretches of hwy and considerable off-road - when we are traveling, the car is quite heavy. I do not want a Defender, Jeep, G or any other 'extreme' and much more capable off-road vehicle ( :roll: ) and I enjoy working on cars. I spent over 10 yrs working as a mechanic mainly on Porsche, MB, BMW. I've autocrossed and raced (not enough time for this lately) Porsches - my other big car thing.

In short:
- I can drive
- I know a little about cars/electrics/electronics
- I don't consider myself extreme (my wife does though :p ), paranoid, or stupid ( hmmm :think: )

Sorry for the rant. Had to get that out. I think this is one tough horse.

ghind said:
I'm not motivated enough to work out how to disable it. Only that I know, in my car a faulty brake pedal (brake light) switch disabled my ABS but left my traction control working. It was great except for the dash warning and I think the brake lights may not have worked (not sure as the switch has a failsafe so maybe they did).

Greg
To recapitulate what I've read:
- pulling fuses creates error messages which can lead to an EAS hard fault/ABS fault which need to be cleared by Testbook, Rovacom, etc.
- disabling an ABS sensor causes an ABS fault that needs to be cleared

So doing the brake switch thing might be a viable alternative - especially if you follow Graham's theory on P-11 of the ABS thread. I've got my lower dash apart and it is raining - I think I'll try this out later today.
 

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I spent most of last week in the Colorado Rockies, in the dirt. I don't recall my ABS kicking in once, the TC beeped a couple times....
 

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shupack said:
I spent most of last week in the Colorado Rockies, in the dirt. I don't recall my ABS kicking in once, the TC beeped a couple times....
The Rockies are my playground, and I too have never felt my ABS kick in, and I've done some pretty extreme trails. My TC will kick in when rock crawling or if I am in loose rock, and owns the trail.

Now that I think about it, I don't remember the last time I actually felt my ABS pulse the brakes. Guess I am just not slamming the brakes in that truck.
 
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I'm not going to weigh in on one side or the other, as i have my own opinion, and that's all it is, my opinion. Being an engineer though, I deal in facts and would like to comment on a few things I have seen throughout this thread.

Stevemfr said:
So you keep rolling and rolling, and rolling, and rolling. You might be rolling for too long and your stopping distance is going to be that of a container ship. Too long to be safe. You might even drive off a cliff.[/i]
If you are driving so agressively that this is a possibility, you must be in possession of a low IQ if you are relying upon the effectiveness or otherwise of the ABS to prevent a cliff dive.


Stevemfr said:
Aside from ensuring that you can steer your vehicle even under heavy braking ABS will keep your vehicle from fishtailing.
[/i]
This is not true. Taking your previous example of excessive speed that stopping in time to prevent driving over a cliff is a risk, it has to do with deceleration and weight transferance. If you are driving fast and brake hard [with or without ABS] the weight shifts to the front of the vehicle, allowing the rear to go "light", if a turn is attempted / performed at excessive speed, the rear end will try to overtake the front end. That's simple physics.

Stevemfr said:
It's def not about removing the ABS (which I am happy to have as a copilot 99.9% of the time), just being able to shut it off in certain circumstances. The situation that the original poster (an Ozzie IIRC) was referring to was descending longer steep inclines off road. I've been in this situation as well - luckily on a shorter incline with lots of runout room. Slush/mud mix that I know I could have done a much better job on with locked wheels. And descending quickly ( less than 20mph - not fast) with no reaction to brakes is unnerving.[/i]
This is exactly the time you want the wheels to be moving and NOT locked. When descending a hill with locked wheels [especially on mud] you accelerate faster and faster as you skim across the surface with no steering and no way of slowing down. Any professional driver will tell you when descending a hill, if you lose traction and start to slide, you have to go against every instinct and accelerate until the wheels match your descent speed and regain traction, then by using engine braking, you can get down in a controlled manner.
 

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The 1995 BMW R1100GS was the first motorcycle equipped with an ABS OFF SWITCH.

I was riding the GS in 1995 on a trail ride in WV. I was about half way down a fairly steep gravel jeep trail when I noticed the ride marker pointing to a single track to the left. As the ABS let go off my every attempt to stop I thought to myself "that's what the off switch is for". Managed to keep it upright, got to the bottom of the hill, disabled the ABS, turned around and climbed back up the hill and continued a great ride.
 

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Discussion Starter #17
This is going to be my last response here as this is silly.

Mr. Range Rover said:
I'm not going to weigh in on one side or the other, as i have my own opinion, and that's all it is, my opinion. Being an engineer though, I deal in facts and would like to comment on a few things I have seen throughout this thread.

If you are driving so agressively that this is a possibility, you must be in possession of a low IQ if you are relying upon the effectiveness or otherwise of the ABS to prevent a cliff dive.
No, you didn't weigh in on one side at all. Remarkable effort on the pros and cons. And thanks, now I can add 'low IQ' to my list above.

First off, I and the other proponents of this aren't making it up. Various manufacturers shut their ABS systems off for off-road use and, as I only discovered the other day, LR put this nifty little paragraph in the owners manual of the P38 (already quoted above but obviously not being read):

• On soft surfaces such as powdery snow,
sand or gravel, and also on very rough
surfaces, braking distances with ABS may
be greater than those achievable with a
non-ABS system. This is because the
natural action of locked wheels on soft
surfaces is to build up a wedge of material
in front of the wheels which assists in
stopping (however, ABS will continue to
provide better stability and steering
control).


Second, the cliff story - which was not something I wrote, btw - is a story used by an experienced off-road driving instructor to illustrate a point. He's not condoning driving aggressively near cliffs. He's saying the same thing LR is above with a slight exaggeration for color. Above all, you seem to have misunderstood completely what he was trying to say. He was not saying rely on your ABS to keep from going over the cliff, he's saying the exact opposite: ABS may keep you rolling on an incline that you could have stopped on by locking the wheels.

I don't agree with the fishtail statement either - as I said, I didn't write it. ABS will allow you to steer while mashing the brakes, but as I've spun an ABS equipped car (due to excessive speed :eek: no cliffs in sight, tho) on a track I do know it's possible - although it is harder to do than w/o ABS as the brake bias is 'modulated' very effectively by the ABS.

Your last statement goes exactly contrary to what the LR engineers seem to think. Please re-read the quote from the owners manual above. Or spend some time actually driving off-road. Or search the internet. Or leave it be and stick to your opinions. I am not going to argue with you any further.


And while I am responding: Dennis and Jsmooth, my 'playground' is in the Vosges, which are smaller mountains only a couple of miles from here. While they are nowhere near to the Rockies (higher cliffs to fall off there :p ), there are plenty of steep inclines to go up and down. I've only had this experience 2 or 3 times, but I've been on a lot of the same trails in one of my RRC's (no ABS) and can compare directly. I don't consider it to be a huge detriment or problem, but it sort of does the same thing to me that skiing on my busted knee does: you look at a steep incline with a touch less confidence. And on trails with almost no room to turn around on and the only alternative to not driving an incline would be to back up for a km or 2... If you keep driving your P38's in the mountains, you'll likely run into this issue sooner or later.
 

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I can imagine if you've had this happen to you it must have made quite an impression. All I can honestly say is that for every steep decline I've ever driven on a mountain trail, I've stuck it in Low 1, and have had zero problems. I tend to drive slower on steep mountain dirt roads as well, as I do not wish to use my brakes too much so I can keep them cool. And I can still honestly say that I've never had my ABS kick in whilst braking offroad, which leaves me totally neutral in this conversation! LOL

Good luck to you though. I love modding, and fit-for-purpose modding always has the most satisfaction.
 

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Where engine braking is sufficient to control your decent speed, I wouldn't think you would have a problem with ABS. First low in the RR is reasonable but not awesome.

The situations I've seen where ABS is not desirable are far too steep for first low to be sufficient. Certainly when towing down the hill I pictured first low isn't enough. Speed runs away even in first low when towing heavy weights down those sorts of steep gravel hills.
 

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Guys, may you please tell me why the offroad trucks that do the DAKAR actually in the T3 category have a disable ABS switch?

I have an example of a Cayenne engaged by a Private owner in events such as Transsyberia that has this kind of switch.

I think those teams may have good engineers who did some test before doing such mods.
 
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