Howdy All,
Now all we have to do is get together and go for a ride. Then after the ride sit around the camp fire and lie about how great we did Now that sounds like an idea to me

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Frank X. Morris
17 Kia Niro
08 Jeep Wrangler 4 door unlimited

I feel I have to chime in here

As for the pix of the ML running Moab trails, I won't believe it is as capable as some think until I see pictures of an ML on Hell's Revenge, Moab Rim, Golden Spike, Poison Spider, the Golden Crack or any other 4 or 4+ rated trail.

If Rallye Raids and high-speed desert-dune running is what you prefer, then Mitsubishi appears to be the spot to look, as they claimed this year's top EIGHT finishers in the Paris Dakar in the car/4wd category. That's the top EIGHT spots. In a row. I'm not trying to be coy, but where did the ML's place (I honestly couldn't find any - mainly because the main dakar site is difficult to navigate and I couldn't find much in the way of information or stats of any relevance beyond the top 10 in each category) - and I would actually like to know.

Being realistic, there are far more trails in the U.S. that offer slow, technical-driving through woods, over rocks, in mud, across moguls, and over hills where you are actually in low range. The opportunity to drive flat out at high-speed on dunes and dirt roads is not near as commonplace for your average back-country explorer, or even your avid trail-rider. Unless you live near the Mojave or the Baja, there really aren't a lot of places like that. It's also usually illegal to drive that fast on dirt roads, and quite dangerous on either if someone happens to be coming the other way. That's why the Paris Dakar is billed "the world's most dangerous race."

Coming from the midwest to the deserts of AZ, I've found all kinds of trails along the way where the order of the day is the more than appropriate motto "drive as slow as possible but as fast as necessary" and you not only need low range, but you wouldn't consider running the trail without it.

Since that other thread of ours was erased, and I had made comments regarding ETS and it's ilk, I have a comment about adding bigger tires to an ML as suggested below (these comments are by no means personal, just point-of-fact):

As G-man (I think) pointed out, ETS requires wheel-spin to activate. On the slick-rock of Moab, this can be, in some cases, deadly. Imagine climbing that 45 degree hill. (Question - was it 45 degrees, or a grade of 45%? There is a vast difference between the two). One wheel starts to slip - just enough to slightly turn the car off of perpendicular to the climb. At this point, depending on the steepness of the hill, that can be the end. Just a little slide off-center (imagine Lion's Back), with wheels already spinning, and you cannot change the laws of gravity and momentum. boom - game over.

The other point here is the idea of adding bigger tires to an ML (or any vehicle with any type of ETS, and for that matter, ABS). In the old (deleted) thread, I pointed out that you have no control over when the ETS will kick in. Will it be 30 feet up the hill where it looks like you might lose traction? Will it be after you start to slide backwards 2 feet? Will any wheels be in the air at that point? You don't know, and you can only predict, because the ETS will kick in when the computer program's algorithm tells it to.

Now you add bigger tires. Your speedometer is now off. Your odometer is now off. Your ABS is now adversely affected. I cannot imagine taking the risk of trusting my ETS to function correctly after I've now PURPOSELY thrown off the entire equation it was based upon (which was designed and calibrated SPECIFICALLY for the MFGs suggested and supplied tire choice, and, most likely, PSI).

When it comes to safety and trail-riding, I believe you should do everything in your power to protect not only yourselves, but those with and around you.

Good discussion going this time - I'm enjoying the lack of name-calling! :-)

Seems like the official Paris-Dakar site is not meant for us who don't know how to use a GPS! Actually, the M-Class finished 2-3-4 in their class, 38-41-42 or something like that overall. They participated in the unmodified category. The Mitsubishis which won all competed in the super modified.

ETS kicks in when the difference between tires is 3mph, 1.2mph at low range. Big tires won't affect the ABS, the ABS sensor only detects lockup and releases the piston when that happens. It's conditions which affect wheel lockup, not tire size. As far as traction is concerned, I don't see why ETS is any different from locked differentials. If you have no traction on one tire then you have no traction. The locked differentials allow one tire to keep spinning, ETS brakes the spinning tire. Either way you have traction on only one side so I don't see much difference. Brent care to explain why locked diffs are more desirable when fording water?

Hmm... Kuan

I feel like I am being set up on the question about water crossings Why would locked diffs be better? I'm not sure what you are getting at. My biggest water crossings were in an old Bronco2. I had water up over the hood on that thing many times. It had no lockers or any thing fancier than a good set of tires. Sometimes it would stall just shy of getting out. This was in a very powerful mountain stream. I personally wouldn't bother with more than the center lock and moderate speed. If it looked like it was going to take more than that I doubt I would drive into it. So I don't think you need either the locker or ETS for water crossings you are likely to encounter on regularly used trails.

The "spinning tire" issue needs to be addressed. With a diff lock one tire does not spin necessarily. As Koly pointed out and I stated at the outset we are talking about low speed manuvers here. With one wheel in the air the locker turns both wheels at the same speed. If you are in this situation spinning a wheel should be the furthest thing from your mind. Gently easing to the next obstacle would be more like it. So the airborne tire will turn the same speed as the tire with traction. This is a very important point that is being passed over by the ML group. Wheelspin is a BAD thing. It means a tire has lost traction and can send you off course, right now. If you have run the 4 - 4+ trails in Moab you would know that a little spin can mean an instant rollover. The positive, driver controlled lockers, are easy to predict. With ETS you wait for the computer to react. I'm sure it is quick, and maybe even somewhat predictable with some experience, but it still requires a pretty good slip to activate. The point trying to be made is that, just a little slip can be very dangerous. Selecting a locker just before you engage the obstacle avoids the slip, clean, quiet, safe, and less damaging to the surface than spinning a tire.

This is not meant to be inflammatory but, I think some of this needs to be experienced. Some of the places I have taken a Gwagen look totally impassable. Words are not sufficient to describe these situations. Lockers are like cheating. I have had to help lifted Jeeps on big tires through before. These jaded folks are amazed by the Gs abilities. I'm sure the ML is a great truck but we are really comparing apples to oranges. There is just no way the ML can compete off-road with the Gwagen, not if I can pick the road.

__________________
1995 G320
1984 280GE
1971 Unimog 416

Nope nope, my mistake. For some reason I thought it was better to lock your diffs before you start crossing water. I think I see it, I haven't experienced it yet. OK I see what you're saying. In a sense it's better safe than sorry, better safe than VERY sorry.

Kuan

Thanks for the info. So, the class that the M's competed in was what? Stock? I only pay attention to the three main classes - Trucks, 4wd cars, and motorcycles, and don't know too much about any of the other classes... Any url's you can point me to?

Some problems here:

Larger tires most definitely affect ABS. The computer that controls the ABS measures wheel speed (larger tires=slower rotation per distance traveled) and compares this to the speed it thinks the vehicle is going to determine when to use and not use the ABS. This, in turn, will affect the ETS system.

For example - w/stock tires you are travelling at 50mph and 3200 rpms. With larger tires, when you are ACTUALLY traveling at 50 mph (remember the speedo will still show 50mph=3200RPM, but in actuality at 3200 RPM you'll be doing a speed higher than 50mph, due to the larger tires) your engine revs may now only be 2900 RPM. So, you'll be farther down the engine's power and torque curve. THEN ADD TO THAT the fact that with a larger radius tire, a given torque at the axle shaft (produced by the motor at a given RPM) will produce less reactive force at the road, due to the fact that the road now has
a "longer lever" to work through in the larger tire radius (thanks Dave ;-)

The ETS will also be affected by the reduced reactive force.

As far as comparing ETS to locking differentials, there is no comparison. Here's a very simplified breakdown of how each works in one scenario:

Scenario - climbing a hill with moguls deep enough to cause extreme articulation - enough so that your front passenger side (PS) wheel and rear driver side (DS) wheel are in the air.

ETS - Without ETS, the two wheels that are hanging in the air will spin, as that is the path of least resistance for the differential. You will be stuck. Then, ETS kicks in and says "whoa! we've got wheel spin. Let's apply the brakes to those wheels that are spinning, and that will help distribute some of this unused power." The ABS braking system then activates and starts braking, which starts to distribute some of the power to the wheels with traction. The problem with this is that each wheel is not getting equal power, as some of that power is lost in the transfer via the braking and spinning.

The other problem with this is that you have already been stopped by the obstacle and have to get the hanging wheels spinning in order to activate the ETS.

LOCKERS - by equally distributing power between all four wheels at all times guarantees that any wheel with ground contact will be pushing the vehicle. You won't stop when those two wheels are airborne. It won't take wheel spin to activate the lockers. Your momentum and traction will not be lost.

Unless you have witnessed both on the same obstacle in person, you really can't get a picture of the difference. And the difference is truly amazing.

Koly,

Let's make sure we're on the same page here. ETS is the traction control which is supposed to mimic locking and limited slip diffs. ABS is antilock brakes right? ETS and ABS do not work together. ABS works only when you stand on the brakes. When the tires lockup, the brakes release. So the only difference being that for the same amount of time that the brakes release in between lockups, the larger tire will roll a little bit more. That's the only difference larger tires will make with the ABS.

I hope this link works:

http://www.dakar.com/2002/us/classementsSpecif.oft?service=DRaceServer&RaceYear=2002&RaceType=DAK&StandingType=SCR_A&StageNumber=1610&Group=T1&Class=T1.1&Category=AUTO

Kuan

In defense of ETS, it is capable of directing 100% of engine torque to a single wheel. I don't think there is a bunch of wasted power when the brakes are used to direct torque. I read in one of Tracy's links, that even after prolonged use the brakes did not overheat. So for what it is, it is very well done.

I think the potential for lost momentum is a concern. I think that more than anything I am really curious to see how well the ML would do. I don't mean that I want to try and rip the bumpers off, but I would like to see ETS in action on a real trail.

Are there any ML clubs that take them out for trail rides?

__________________
1995 G320
1984 280GE
1971 Unimog 416

Okay G, when it thaws out maybe I'll ask some of our M-friends if they wanna come up there? What say you?

Kuan

We are indeed talking about the same thing. ETS (Electronic Traction Control) and ABS (Anti-Lock Braking System) are intertwined. I do not believe that ETS is supposed to 'mimic' a locking differential. It certainly doesn't, as it allows wheels to spin and applies brakes, thusly, not distributing all the power evenly across axles (power is still being sent to the wheel w/the brakes applied - some of the power is therefore lost). A locking differential dispurses equal power all the way around. I could see ETS as a mimic for a limited slip differential, but not a locker.

As to how they are connected:
When ABS senses locked brakes, it releases and re-applies the brakes to keep you from sliding. When ETS senses wheel spin, it basically co-opts the ABS and uses it to apply and release the brakes. They both use the same system of pumps, pads, and computers to activate/deactivate the brakes. Both use the same (or similar) computer algorithm to know when to activate. Changing one of the major factors in that equation (overall wheel size) will definitely have an effect. To state that the only difference a larger tire will have on ABS is that it will roll a bit further is a bit non-chalant. Longer stopping distances and an incorrect application of the ABS's spec'd functionality is the result. And if you're standing on the brakes to try to stop, it usually means it's an emergency. With bigger tires, (regardless of ABS), it's going to take a longer distance to stop. To me, that is an extremely important change.

A small change in tire size (say, going from the stock 29" ML size tires to a 30 or even 31) will not be as noticeable as something more dramatic. It will still have an adverse affect, but, especially on day-to-day driving, not as evident as on the trail, where you WILL notice it. However, many trails I run require tire sizes of 33" or more, if for ground clearance only. With a 13% change in tire size, (besides the obvious fact that your low range is now no longer very low and you wouldn't be able to make many of those climbs), I would be scared to entrust my life to components spec'd for a drastically different setup.

Again, I'm w/G-man here. The loss of momentum, the beginning of wheel spin, and the potential for danger is too much for my comfort level. The only real way to understand is to see the two side-by-side on the same obstacles. The difference will astound you.

Question for G-Man:I was not aware of any ETS that was able to apply 100% of the engine torque to a single wheel. I would think that would be the easiest way to break an axle... Power still needs to be sent to the spinning wheels in order to apply the brake to them so the differential kicks in and takes the path of least resistance, or at least dispurses the power. Maybe I am misunderstanding something, but that is how I have seen all ETS systems function. However, if the engineers at MB came up with some other method, it wouldn't surprise me.

As to brakes not overheating - how long are the brakes applied to the spinning wheel? Nowhere near long enough to overheat them. I don't think the brakes are used nearly as hard in an ETS situation for a few seconds when compared to stop-and-go traffic braking.

Kuan - thanks for the Dakar link! But from that page, it appears that only 5 competitors in the 'scratch' field actually completed the event? Is that true? That site is really quite terrible. Perhaps if I spoke french it might make more sense?

On the ETS. Koly I think you covered it. With the brake applied (airborne wheel locked) 100% of the torque flows out the other way. But I see your point, if the wheel with traction turns, the computer must allow the airborne wheel to turn within 1.2 mph of the other. Obviously you don't get 100% in that case. Advertising hype? Works in theory? I'm not sure. On the axle breaking, MB has the technology to limit torque in the driveline. On the Europa G500s I know that they limit engine torque in low range, with the front locker engaged, as to not break anything. I suspect a similar tact was used on the ML. I know my new Chevy pick-up limits torque in low range too.

Kuan, Thaw??? Geez I was just out on the track today with some fresh snow(love those lockers). I had a guy from Allison Transmissions looking at my Chebby truck today. He was a motorhead too and was talking about his sons CJ-5 and such. Just before lunch I took him on the course in the Gwagen. He hung on a lot and commented that he didn't figure his sons Jeep had any business on that track

I'd love to see a couple MLs show up. Don't play it up too much, it is just a dirt pile in a corn field We could fill in the holes a little and see some good articulation from the MLs. It would be a perfect way to see the ETS at work. There are also a couple pretty good side hills that lean you over. I'd be up for it anytime!

__________________
1995 G320
1984 280GE
1971 Unimog 416

I've not heard of this torque limiting - I am more than intrigued as to how a system like this would work - any URL's your info you can point me to or further descriptions? I'd like to know more.

Sidenote:
Where is Verndale? it's quite funny that three of the active posters here all have Minnesota ties - I'm originally from MN, and lived mainly in DT Minneapolis for quite a while before moving to AZ.

Well, that is a tough one.I know about the torque limiting on the G from Jason @ Europa. I don't think I have seen it in print. I know it is used on my chevy because I had it thwart my efforts once. 300hp truck with 520 lb/ft of torque that can't spin its tires on loose dirt, hmmmm where did the power go. The forum dedicated to those trucks revealed that engine torque is limited in low range because of the torque multiplication. I suspect that finding out about the chevy would be easier than finding similar G material.

I know it exists, I have seen it work, I am not crazy I'm not sure how excessive torque is determined or controlled, but now that you mention it, it sounds like a subject I may follow up on.

Beautiful Verndale MN, located right in the center of the state. It is between Staples and Wadena on Hwy 10. I am about 30 miles due west of Brainerd. It may not make your map as the pop. is under 500. I actually live in Staples and work in Verndale. We moved here about 7 years ago from NE Mpls, off Broadway between University and Central. It is much quieter here

__________________
1995 G320
1984 280GE
1971 Unimog 416

I think you're missing the simplicity of ETS-4. The front and rear differentials are "open" design, in old days we old hot-rodders just called them "single-spin differentials" as is the transfer case, if you don't have a problem visualizing a transfer case as a kind of differential. With the tranfer case, if you have no problem realizing that the G-Wagon transfer case "locks", then you should have no problem visualizing the ML tranfer case as "open".
OK, so the left front wheel is in the air, or on glare ice. The tire loses traction and begins spinning. The ETS control unit "sees" this and using the pump in the control unit, stops the spin. The power, due to the "open" design of the front diff, transfers to the other 3 wheels, not just the other front, it is all shared. Actually, a small amount of power will go to the wheel that was spinning, as the ETS is constantly analyzing if the spinning tire now has traction, if you've seen this demo'd, you will have noticed the tire that was spinning "chattering" for lack of a better word, as the ETS tests for traction.
To continue, if the other front tire is now on glare ice (guess they can't both be in the air! ((well they CAN, you know what I mean)) the wheel speed will be seen by the ETS control module, and the process continues, the brakes are also applied to the other fron wheel, and because of the open design of the transfer case, the power is now going to just the rear axle, except for the small amount to the front as the traction to the front tires is monitored. And if traction is further lost at one of the rear wheels, then that brake will also be applied and power transferred to the wheel with traction. I am unsure what happens when your traction drops on that wheel, I believe the wheels will probably all spin because the ETS computer now doesn't know what good traction looks like anymore, so to speak.
The good thing about the ETS on the ML is that the mechanics of it are pretty simple and light, it's the electronics that do all the dirty work. I don't think how ETS-4 works can be categorized as imitating either a locker or a limited slip differential, it's really a unique thing.
Gilly

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Good points Gilly...

In my explanation, I neglected to point out exactly how and where the power transfers to from the spinning wheel... for simplicity I described it the way I did... your ice analogy is a good one to really show off and help explain ETS.

G-man, if you poke around any more regarding toque limiting, I'd be curious to hear what you find out. Just an interesting subject, I think - trying to figure out how those clever engineers manage to dissipate that energy somewhere is pretty cool . And after your location spotting of verndale, I have a good idea right where you're located - lots of good trails up in that neck of the woods. I had a girlfriend who's family lived in Brainerd, and when we'd go visit, I'd usually find a way to sneak out and run a trail

BTW (completely unrelated) - have you ever gone to the Ojibwe SCCA Rally?