I know this video does not have a BMW in it but this shows how much better the VW Haldex system is than the other competitors.

http://briskoda.net/forums/topic/159259-4x4-systems-tested/

And remember that that Passat in that video has a much older system than the Yeti.

I too use winter tyres and can't begin to tell you how much better then are in cold temperatures than the summer ones. And yes I don't even mention snow as there is now comparison then. The winter tyres are eons better.

This is actually a very good video, it certainly shows the Haldex system in good light although the Subaru faired better in the test. As you point out the Passat had the older Haldex system, does the Haldex 4 cure the issue of no drive with only 1 wheel gaining traction or does this remain an issue to to the asymmetric layout?

This is actually a very good video, it certainly shows the Haldex system in good light although the Subaru faired better in the test. As you point out the Passat had the older Haldex system, does the Haldex 4 cure the issue of no drive with only 1 wheel gaining traction or does this remain an issue to to the asymmetric layout?

I think Agerbundsen tried to answer that in his post of the thread the video is from linked above:

"I assume that the Passat, like the Yeti, does NOT have a transfer case or center differential. The output to the front and rear axles are always tied together. In normal dry conditions, the front wheels drive and the Haldex coupling is open, transferring only the power to the rear, which is caused by internal friction in the open Haldex. For the Yeti, most situations are rather clear to me - except one. Loose traction on one rear, and the rear axled Haldex differential lock ties the rear axle halves together and rotates both rear wheels at the same torque. If there is no traction on the front axle, the torque is transferred to the rear - and the front wheels should rotate at the same speed as the rear with traction. The question comes if only one front wheel has traction and the other three not. If the electronics are smart enough to brake the spinning front wheel, then all is well and the car would transfer the torque to the other front wheel. If not, then the same would happen as happened to the Passat in the video.

My guess is that the Yeti is smart enough and does the right thing."

I think Agerbundsen tried to answer that in his post of the thread the video is from linked above:

"I assume that the Passat, like the Yeti, does NOT have a transfer case or center differential. The output to the front and rear axles are always tied together. In normal dry conditions, the front wheels drive and the Haldex coupling is open, transferring only the power to the rear, which is caused by internal friction in the open Haldex. For the Yeti, most situations are rather clear to me - except one. Loose traction on one rear, and the rear axled Haldex differential lock ties the rear axle halves together and rotates both rear wheels at the same torque. If there is no traction on the front axle, the torque is transferred to the rear - and the front wheels should rotate at the same speed as the rear with traction. The question comes if only one front wheel has traction and the other three not. If the electronics are smart enough to brake the spinning front wheel, then all is well and the car would transfer the torque to the other front wheel. If not, then the same would happen as happened to the Passat in the video.

My guess is that the Yeti is smart enough and does the right thing."

I was really just looking for some confirmation as he has a ''guess'' that the Yeti is smart enough. I found this video not sure if anyone here has noticed it before, the X5 does quite well in it, second (I think) furthest up the hill to an Allroad.

Edited 23 May, 201115 yr by servicepoint

As I understand it, the Yeti is the same as the Octavia Scout and 4x4.

The front wheels are controlled by an Electronic Diff Lock (i.e. dabs on the brake on the spinning wheel, actuated like the ESP), and so progress will be made if either one of the front wheels has traction.

The problem is that if both fronts have no traction, both rears need traction because the rear axle has an open diff. While an electronically controlled rear differential is a part of Haldex 4, it is not deployed in the Octavia or Yeti to my knowledge, it is just the upgraded Haldex clutch on the drive to the rear axles.

Can anyone confirm or otherwise? This is shown @ http://briskoda.net/forums/topic/188394-haldex-iv/

Edited 23 May, 201115 yr by London Les

To be honest I think we have now got to the stage where we are arguing semantics. Can we not accept that the Yeti is bloody good and it does everything it says on the tin?

To be honest I think we have now got to the stage where we are arguing semantics. Can we not accept that the Yeti is bloody good and it does everything it says on the tin?

+1

To be honest I think we have now got to the stage where we are arguing semantics. Can we not accept that the Yeti is bloody good and it does everything it says on the tin?

+1

Ok so where are we with this, does anyone actually know for sure what the Yeti system is.

Haldex Gen 4 or previous?

Will ABS act as a locked LSD on the rear axle?

Is there a limited slip clutch on the rear axle differential?

Is the electronic diff lock only on the front?

A few conflicting opinions on this thread so I've tried to pull them together as best I can for someone to clarify as I'm getting more and more confused but determined to be clear in what I'm buying into.

Please be patient with me and my lack of knowledge on the Haldex system.

All Yeti literature states Haldex 4............

refer to the Haldex website for more info...

Add.

Thanks for those kind words, peoples.

I've just changed the front tyres on Dewi and now have Kumho's fitted. They are a not marked as All Season but are much more agressive than those fitted previously. Now all I've got to do is wear the back ones out!

Ideally the new tyres should have been fitted to the rear.

No - I think it's good to understand the mechanics and their limitations.

I've read NZ website which talks about an LSD on the yeti - that would be supported by this demo:

But that's not very convincing - it would be better if the Scout could do the same on a hill.

Rockhopper - re my steep hill - have a look at Canonbie Road on google streetview especially to the East side. Amazing for so close to central London I reckon.

Ideally the new tyres should have been fitted to the rear.

Blimey, Onesque, you're brave. It takes a real geezer to start the debate over where the two new tyre should go. I didn't fancy spending all night trawling the net to add up all the 'pro fronts' vs the 'pro rears' but just spent five minutes and would agree that, almost certainly the "new on the rear" lobby has it. There are countless tyre authorities, AA, reputable tyre companies and manufacturers agreeing with that...but also a few, equally, seemingly, authoratative sources taking the opposite view, with Joe Public on the forums mostly favouring the rear.

The most obvious answer is to swap them round to equalise wear and change all four at once. That way you don't have to enter the debate...and I always have a slightly warm and satisfied feeling knowing I've got four brand new boots on board. Could be a rubber fetish or the smell of new rubber under my nose - or, more boringly, you know you've got good grip for good while.

Blimey, Onesque, you're brave. It takes a real geezer to start the debate over where the two new tyre should go. I didn't fancy spending all night trawling the net to add up all the 'pro fronts' vs the 'pro rears' but just spent five minutes and would agree that, almost certainly the "new on the rear" lobby has it. There are countless tyre authorities, AA, reputable tyre companies and manufacturers agreeing with that...but also a few, equally, seemingly, authoratative sources taking the opposite view, with Joe Public on the forums mostly favouring the rear.

The most obvious answer is to swap them round to equalise wear and change all four at once. That way you don't have to enter the debate...and I always have a slightly warm and satisfied feeling knowing I've got four brand new boots on board. Could be a rubber fetish or the smell of new rubber under my nose - or, more boringly, you know you've got good grip for good while.

I did think twice before posting as I did not want to open up the debate again or hijack this thread by changing the topic.

I used to be in the 'fit new tyres to the front' camp until I went on a Tyre Technical Course at Michelin and was taught the errors of my thinking. They had a saying which I always remember "Best to Back".

In very basic terms you should try to ensure that there is no likelihood of the rear of the vehicle breaking away from you as this is almost impossible to control. Hence new tyres with better tread should be fitted to the rear, 'Best to Back".

I was just surprised by Graham's suggestion the new tyres had been fitted to the front?

Phil

I did think twice before posting as I did not want to open up the debate again or hijack this thread by changing the topic.

I used to be in the 'fit new tyres to the front' camp until I went on a Tyre Technical Course at Michelin and was taught the errors of my thinking. They had a saying which I always remember "Best to Back".

In very basic terms you should try to ensure that there is no likelihood of the rear of the vehicle breaking away from you as this is almost impossible to control. Hence new tyres with better tread should be fitted to the rear, 'Best to Back".

I was just surprised by Graham's suggestion the new tyres had been fitted to the front?

Phil

I've started a new thread for this as it is quite interesting. Please keep this one OT from now.

http://briskoda.net/forums/topic/202473-pair-of-new-tyres-fit-them-to-front-or-back/

I did think twice before posting as I did not want to open up the debate again or hijack this thread by changing the topic.

I used to be in the 'fit new tyres to the front' camp until I went on a Tyre Technical Course at Michelin and was taught the errors of my thinking. They had a saying which I always remember "Best to Back".

In very basic terms you should try to ensure that there is no likelihood of the rear of the vehicle breaking away from you as this is almost impossible to control. Hence new tyres with better tread should be fitted to the rear, 'Best to Back".

I was just surprised by Graham's suggestion the new tyres had been fitted to the front?

Phil

Thanks for that explanation and description of your experience at the Michelin course.

Perhaps the matter should rest there, as you say, for fear of hijacking the topic.

EDIT. Just seen Johann's reply.........all noted with thanks.

Edited 24 May, 201115 yr by oldstan

This is actually a very good video, it certainly shows the Haldex system in good light although the Subaru faired better in the test. As you point out the Passat had the older Haldex system, does the Haldex 4 cure the issue of no drive with only 1 wheel gaining traction or does this remain an issue to to the asymmetric layout?

The asymmetric layout argument sounded extremely weak to me. It was not explained how torque steer at the front could affect the ability of the rear wheels to deliver drive. Some of the other technical "explanations" were poor as well, like the justification for the Forester not being able to climb the ramp when all four wheels were slipping. The stuff about "power will always take the path of least resistance", while valid enough in itself, was just waffle - all four wheels were on rollers so there was simply no traction! I also noticed that they didn't do the "only one wheel with traction" test with the Forester (although they did with the Legacy).

It all smacked to me as being very much a marketing puff piece cunningly contructed with just enough engineering-like content to sound convincing to an uncritical audience.

All Yeti literature states Haldex 4............

refer to the Haldex website for more info...

I don't think there is any doubt that the Yeti has Haldex IV. What is still unclear in my mind at least is how the drive to the rear works. In the paragraph that Johann quoted above, Agerbundsen mentioned the "rear axle Haldex differential lock". However, other posters on other threads - such as here and here - have suggested that the differential on the Yeti's rear axle does not lock, rather that traction is controlled in the same way as at the front ie by braking a wheel which is slipping. Additional potential for confusion seems to arise from the fact that Haldex XWD as used on the Saab 9-3 and the Opel Insignia uses both the Haldex IV coupling and the Haldex electronic Limited Slip Differential (eLSD) - but AFAIK that's not the setup that the Yeti has.

Bottom line: I am still unclear at to whether the Yeti has a clever differential on the rear axle, or a conventional differential and clever brakes.

However, it all seems a little academic when, in the real world, the car can do the sorts of things it does in these vidoes:

and

(in particular at approximately 5min 30s onwards)

I just point it in the right direction and press go. It seems to work and it doesn't make my brain hurt. Don't over complicate life.

I just point it in the right direction and press go. It seems to work and it doesn't make my brain hurt. Don't over complicate life.

+1

ejstubbs,

''The asymmetric layout argument sounded extremely weak to me. It was not explained how torque steer at the front could affect the ability of the rear wheels to deliver drive. Some of the other technical "explanations" were poor as well, like the justification for the Forester not being able to climb the ramp when all four wheels were slipping.''

''It all smacked to me as being very much a marketing puff piece cunningly contructed with just enough engineering-like content to sound convincing to an uncritical audience.''

It was a marketing piece without question,lots of the videos are, it also doesn't make it wrong.

As for the video you posted, this too is a marketing video and a poor one at that, I certainly wouldn't buy a car on the strengths of what it shows (it does however confirm the Yeti has a Haldex Gen iv), some of the amatuer videos available on youtube show the Yeti performing better.

On asking the question,

When equals amounts of torque is sent to the four wheels but all of the wheels have different weights and elements acting on them the equality is reduced. Subaru has developed the Symmetrical All Wheel Drive which is a perfectly (or very close to) balanced all wheel drive system. There are no external parts, axles or shafts on either the left or right to offset the symmetry as there are in other all wheel or four wheel drive systems. The entire drivetrain is along the center line of the vehicle and balances the weight and power distribution on both sides. The weight of the drivetrain is also spread out from front to rear. It may not be symmetrical from front to rear but it is better than many all wheel drive systems.

Examination of other manufacturers’ AWD vehicles reveals that a good many of them have transversely mounted engines that necessitate changing the direction of torque from the engine by 90 degrees. These are primarily front-wheel-drive vehicles with rear-wheel drive on demand.

Even vehicles with longitudinally mounted engines tend to have external driveshafts for the front wheels, along with other components outside the centrally located powertrain.

Edited 24 May, 201115 yr by servicepoint

It was a marketing piece without question,lots of the videos are, it also doesn't make it wrong.

No, but it does mean that it is less likely to tell the whole story. And I don't believe any reasonable explanation has yet been offered for the statement in the video that the asymmetrical drive train was the reason for the Passat not meeting VW's claims.

As for the video you posted, this too is a marketing video and a poor one at that, I certainly wouldn't buy a car on the strengths of what it shows (it does however confirm the Yeti has a Haldex Gen iv), some of the amatuer videos available on youtube show the Yeti performing better.

I wouldn't buy a car on the strength of a video, full stop. The first video I posted (the flickr link that didn't embed in the posting like the Youtube one did) is an amateur video.

On asking the question,

What question? What I would like is for someone to give me definitive (ie preferably with independent evidence) answer as to the drive system in the Yeti's rear axle . The information you provided doesn't help me there I'm afraid - it seems to be about dynamic balance and weight distribution, as well as being perhaps a litte defensive towards Subaru. If my earlier posting came across as attacking Subaru then that was not my intention; my car before the Yeti was an Impreza and I kept it for ten years so I think I qualify as someone who appreciates the features and benefits of their technology if not necessarily their marketing department . I'm just trying to get an asnwer to what on the face of it is a fairly straightforward question but which so far seems to be beyond the normally impressive capability of this forum to answer

The Yeti brochure states:

EDL: the Electronic Differential Lock continually compares the rpm of the drive wheels, and if it identifies a difference between them which could lead to an individual wheel spinning, for example if the two wheels are on different types of surface or accelerating on wet leaves, the system brakes the wheel affected until uniform rpm of all drive wheels is restored.

But it does not state where this little megafter lives! And even so all it is to my mind is the very same ABS sensors that also control the Tyre Pressure Monitor that senses the spin and the central computer telling an individual wheel to be braked. So there is no megafter that looks like a differetial anywhere to be found. :no:

I'm sure TP will come with a long answer with pictograms shortly!

Technically I don't understand exactly how the haldex system works on the Yeti but I do know for sure that it got me down a spanish mountain road after a massive flood caused a pretty bad landslide, has gotten me on and off sand, shingle and pebble beeches, has easily got me across wet fields, through the worst that the Swiss alps had to throw at me and even around an off road course filled with specialist, custom built 4x4's. So, for me at least; it works very effectively indeed.

The first video I posted (the flickr link that didn't embed in the posting like the Youtube one did) is an amateur video.

You calling me an amateur?................

No, but it does mean that it is less likely to tell the whole story. And I don't believe any reasonable explanation has yet been offered for the statement in the video that the asymmetrical drive train was the reason for the Passat not meeting VW's claims.

In the video they only ''suggested'' that possibly the reason the Passat didn't meet the claims of VW were that in 2007 the engine was configured transversly with the transmission moved towards the driver side, thus having obvious potential for torque steer, as they can't find any other reason for the lack of drive, perhaps this is why.

''I wouldn't buy a car on the strength of a video, full stop. The first video I posted (the flickr link that didn't embed in the posting like the Youtube one did) is an amateur video.''

I wasn't suggesting you would buy a car from a marketing video, it was not my intention for you to take it this way, I perhaps should have been clearer, I was suggesting that we know these are marketing films and we must form our own opinions by taking any unbiased information available from them. Most marketing films and brochures are as you put it cunningly constructed, I'm sure we have all at some time picked up a car brochure for information knowing that it will not advise of any depreciation.

Edited 24 May, 201115 yr by servicepoint

What is still unclear in my mind at least is how the drive to the rear works. quote]

There was a very detailed discussion of the drive systems some time ago, but I am not good at going back and finding the thread. Also, the Haldex site used to have more detailed descriptions, but alas, no more.

Here is a brief description as I understad it:

The drive to the rear axle is from a power take-off on the gear box. No center differential, just a fixed output shaft. So the drive shaft to the rear axle is always rotating, driven from the gear box. Withe the Haldex coupling in the normal open condition, only a small amount of power is delivered to the rear axle, probably determined by friction in the Haldex coupling.

The Haldex coupling, rear differential and limited slip coupling are all built into the same rear differential housing, supplied by Haldex. The electrically powered hydraulics operate both the "Haldex IV" couplng, delivering power to the rear axle and the limited slip coupling, locking the two rear drive shafts together.

The number of inputs to the system and the interaction of the various control scenarios are very complex and confusing. If you look at various videos, where the YETI lifts a rear wheel completely off the ground, notice that this wheel does not rotate. If the two axle halves were just locked together, that wheel should rotate at the same speed as the other wheel on that axle - but it does not.

In Johann's video of fooling around on a snow covered parking lot, TCS is off, and clearly all four wheels are driving and spinning = Haldex coupling and LSD in action. If you try to do the same with TCS on, the result is very confusing, as the ECS (?) control tries to figure out where you intended to go and selectively brakes individual wheels in some sequence, trying to stay on track. This works well in "normal" road situations, but not where you are deliberately trying to go well beyond available tration as Johann demonstrated. When there is not enough friction between road and tyres, the electronics have nothing to work with.

A rather complete description of the Haldex 4 system here: http://en.wikipedia.org/wiki/Haldex_Traction

Originally developed for SAAB as XWD, but released after the first year exclusivity agreement as Haldex 4. The LSD (Limited Slip Differential) clutch is clearly inclúded in the Haldex 4.

Edit: Addition of Wikipedia reference.

Edited 25 May, 201115 yr by Agerbundsen