Why do some say changing springs destroys EDC shocks??

[lucid]

Originally Posted by swamp2

Trying to get back to some common ground, agreement or disagreement, this is where I seem to differ significantly from both you and jm1234.

Yeah, we should cool this down. I think there is actually more agreement than disagreement on the table.

Originally Posted by swamp2

Can we at lesat separate the ride height issue from the spring stiffness issue? I think I "proved" with a simple thought experiment that a spring that only changed the ride height could not be "detected" by the EDC system nor enough to alter its performance.

I looked through your posts, and can't pin down which thought experiment you are referring to exactly? Are you referring to BMW swapping spring during testing? If so, yes, they must have surely done that. However, once they nailed down what they wanted, they could have optimized things further for that stiffness.

[swamp2]

Originally Posted by lucid

Yeah, we should cool this down. I think there is actually more agreement than disagreement on the table.

Optimistic. Don't think so, but it doesn't matter does it?

Originally Posted by lucid

I looked through your posts, and can't pin down which thought experiment you are referring to exactly? Are you referring to BMW swapping spring during testing? If so, yes, they must have surely done that. However, once they nailed down what they wanted, they could have optimized things further for that stiffness.

Imagine lots of passengers, full fuel plus max cargo load vs. empty tank, no cargo and driver only. You will have a significant offset of the entire suspension including shocks. It will still work fine.

[swamp2]

Here is our first guinea pig. EDC = sport at least "feels" better with aftermarket springs. This is not going to be an issue.

http://www.m3post.com/forums/showpos...98&postcount=7

[lucid]

Originally Posted by swamp2

Imagine lots of passengers, full fuel plus max cargo load vs. empty tank, no cargo and driver only. You will have a significant offset of the entire suspension including shocks. It will still work fine.

Of course it works "fine." What did you expect it to do, bounce around like the camry in that video? The question is does it perform as well is could? Meaning, if you knew the new offset with the additional weight, could you write better code for the damper to make it perform better? My answer is I don't know since I still don't understand how the system works exactly. We really do not have enough information.

Plus, how much extra offset do you really think you will get on this car with 500lbs delta load--even 0.25"? People are talking about dropping these cars 1.5"-2.0".

[lucid]

Originally Posted by swamp2

Here is our first guinea pig. EDC = sport at least "feels" better with aftermarket springs. This is not going to be an issue.

http://www.m3post.com/forums/showpos...98&postcount=7

Oh, come on Swamp, you are more thorough than that. That's just one guy saying everything is better after dropping some serious cash on a mod (I already referenced that thread in post #33 btw). What exactly did you expect him to say? Has he actually tested the car in an objective way? Of course not. I am not saying he is wrong, but you can't say he is right either.

[swamp2]

Originally Posted by lucid

Oh, come on Swamp, you are more thorough than that. That's just one guy saying everything is better after dropping some serious cash on a mod (I already referenced that thread in post #33 btw). What exactly did you expect him to say? Has he actually tested the car in an objective way? Of course not. I am not saying he is wrong, but you can't say he is right either.

Of course I am, all I did is quote the guy with "feels" in quotes for emphasis and to note it was his words. As well I called him a guinea pig. How much more conservative could I be?

On ride height: I suspect max permissible load to drop the car pretty close to the same amount as a "sport" drop. Again only trying to find common ground that we agree that the EDC system is not able to discern ride height offsets and this does not affect the robustness of it. The lowering accomplished by the weight will help the car and handling by lowering its CG and improving its frontal area but will hurt it by the extra moment of inertia and higher centifugal forces. It won't hurt the handling by messing up EDC function.

[dcaero]

I'm pretty sure all this talk/disagreement boils down to the compromises that every engineer makes on every decision. Yes models work well. Are they 99.99% accurate? Of course not. Could you have a look-up table to reduce cost and complexity? Sure but would it work as well? You get the idea.

I'm pretty sure you guys are all preaching the same ideas, and that if you all sat in a room together with all the information you would reach a comprise...just as the BMW engineers did. Either way the thread has been a fun read after work. It's nice knowing there are other professionals roaming around on these forums.

[lucid]

Originally Posted by dcaero

I'm pretty sure all this talk/disagreement boils down to the compromises that every engineer makes on every decision. Yes models work well. Are they 99.99% accurate? Of course not. Could you have a look-up table to reduce cost and complexity? Sure but would it work as well? You get the idea.

I'm pretty sure you guys are all preaching the same ideas, and that if you all sat in a room together with all the information you would reach a comprise...just as the BMW engineers did. Either way the thread has been a fun read after work. It's nice knowing there are other geeks roaming around on these forums.

Corrected your post above.

Yes, every design decision is indeed essentially a trade-off between competing requirements...

[lucid]

Originally Posted by swamp2

Again only trying to find common ground that we agree that the EDC system is not able to discern ride height offsets and this does not affect the robustness of it.

It does seem that EDC does not detect ride height somehow, but then we don't know that there isn't a position sensor somewhere. The info Greg posted is helpful, but it might not be complete.

Originally Posted by swamp2

The lowering accomplished by the weight will help the car and handling by lowering its CG and improving its frontal area but will hurt it by the extra moment of inertia and higher centifugal forces.

Putting the EDC performance/ride height/spring stiffness discussion aside, I am still really puzzled that the car is not riding as low as a 335. I don't buy the bumper/spoiler explanation. It should be trivial to design around those--the way they handled it for the 335. It is clear that there is much to be gained by lowering the CG, and there has to be a pretty solid functional reason why they didn't go for it...

[serven7]

I dont know much but I do know that the RD springs I put on today look damn good(not too low) and the ride isn't bad but I still need to take it in for an alignment it pulls to the right like my golf swing.

[dcaero]

Originally Posted by lucid

It's nice knowing there are other geeks roaming around on these forums.

As far as engineers go, is there really a difference? haha

[IWC Doppel]

Guys,

I have tried to help by providing an objective comment on how the car feels. For the record I actually do have a degree in Automotive engineering and have built F1 engines in the dim and distant past. But my comments were purely subjective.

A good friend who has owned a large number of BMW's including 3CSL's two he raced drove the car and has ordered the springs following. We both agreed on the following :

1. There is less jitter on full stiff and the feeling of being usettled on anything but a super smooth road on the stock springs. The feel is better on full stiff with the H&R springs.
2. It does not work well on comfort (I personally never drove the car in this mode)
3. It feels more planted and has more steering feel
4. Body roll is noticeably reduced
5. Comfort and ride feels a little different but does not feel noticeably worse and we both prefer it overall to stock

For both of us an improvement over stock

Regarding damaging the shocks I do not know how the stock shocks work so can't really add to the debate about 'destroying' the shocks. BUT the 15-25mm ride height reduction will be seen on a stock car on most journeys so I cannot see a logical reason for potential damage. The shocks have not bottomed out since fitment, so again I see no reason for potential damage.

Shocks are primarily about damping, with EDC this is variable I would be surprised if this also varied with ride height, very surprised and I can see no reason why it would be desirable to do so unless you intend to use the damper as support for the spring rate under significant bump. This is usually done by the rate of movement, exactly what the damper is all about. As I write I can think of a number of arguments why this would make no sense.

My only thought on potential damage would be bottoming dampers and I have not experienced this yet



I will see if I can find out more abut the EDC design and comment further.

[lucid]

Originally Posted by IWC Doppel

Guys,

I have tried to help by providing an objective comment on how the car feels. For the record I actually do have a degree in Automotive engineering and have built F1 engines in the dim and distant past. But my comments were purely subjective.

A good friend who has owned a large number of BMW's including 3CSL's two he raced drove the car and has ordered the springs following. We both agreed on the following :

1. There is less jitter on full stiff and the feeling of being usettled on anything but a super smooth road on the stock springs. The feel is better on full stiff with the H&R springs.
2. It does not work well on comfort (I personally never drove the car in this mode)
3. It feels more planted and has more steering feel
4. Body roll is noticeably reduced
5. Comfort and ride feels a little different but does not feel noticeably worse and we both prefer it overall to stock

For both of us an improvement over stock

Regarding damaging the shocks I do not know how the stock shocks work so can't really add to the debate about 'destroying' the shocks. BUT the 15-25mm ride height reduction will be seen on a stock car on most journeys so I cannot see a logical reason for potential damage. The shocks have not bottomed out since fitment, so again I see no reason for potential damage.

Shocks are primarily about damping, with EDC this is variable I would be surprised if this also varied with ride height, very surprised and I can see no reason why it would be desirable to do so unless you intend to use the damper as support for the spring rate under significant bump. This is usually done by the rate of movement, exactly what the damper is all about. As I write I can think of a number of arguments why this would make no sense.

My only thought on potential damage would be bottoming dampers and I have not experienced this yet



I will see if I can find out more abut the EDC design and comment further.

Thanks for the clarification and new information about your mod.

The suggested mode of failure for the shocks is that they might experience higher forces with stiffer springs. Higher damper forces would be caused by higher damper piston velocities. We don't have any specs on the shocks, so we don't know what the safe operation range is. So, I personally don't think we can really conclude anything about what might happen to the shocks over time with aftermarket springs.

[IWC Doppel]

I am not sure why a stiffer spring would place higher accelerations on the damper ?

For a given bump the stiffer spring would move less and pass more load into the shell. The damper would accelerate less as it will be required to move less over the same bump. There will be more forces on top mounts etc but the damper should have less movement and hence acceleration.

I am still not sure what exactly EDC does other than adjust the bump and rebound settings. The interesting point about the dampers is how they adjust in comfort or normal where they are believed to adjust damping during operation. Maybe the acceleration point refers to the sensors and their impact on variable damper settings. But again in full setting it does not lessen the damping to provide a more comfortable ride, I assume this means that the damper is full stiff and cannot stiffen any further without revalving or other mechanical changes.

If I was a betting man I would suspect that driving on full stiff on poor road surfaces with stock springs would provide more wear than any setting with marginally shorter and stiffer springs on better surfaces.

I also wonder how the US vehicles might vary to Euro spec cars, possible the dampers have different settings. I do know that a lot varies between US and Euro market specs for BMW's and Porsches.

What are peoples views of ride and feel in mid vs Full EDC for example ?

Accepting that subjective comment is only that

[IWC Doppel]

Oh, By the way I am not defending H&R or supporting any mod I do, if I didn't like them they would be off and in a box in the loft !

There are lots of things I have bought in the past I have regretted !!

If I am honest I would not have considered changing if they did not improve the looks (IMO)

[JEllis]

Great discussion here and some good info.

The best evidence or "source data" is probably the many EDC suspensions on both M5's and M6's that have been modified. So far I have not heard of any horror stories involving modified M5/6 EDC suspensions.

My gut tells me that in the long run a modified EDC shock/strut will wear faster than an un-modified shock/strut. However, EDC is a unique animal and my experience is based on none adjustable stock shocks/struts that wear much faster with aftermarket springs. Again, my experience is also with springs where the manufacturer suggested afermarket shocks and struts and this case is also unique due to the fact that H&R and RD are certifying their sport springs for use with the stock shocks and struts.... Although there is probably a conflict of interest, I would be interested to see what their responses to these questions would be.

Jason

[IWC Doppel]

I have now driven the car with H&R's for nearly 7,000 miles.

Zero problems, I came back from Europe with over 100 bottles of wine and a car FULL of cases and a passenger. The car was loaded up to the head restraints ! and in the footwells. Although the car was low I drove at speed without bottoming or any suspension issues. I will post a picture when I download the girlfriends pictures

H&R well done