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      09-25-2013, 09:51 AM   #1
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Adaptive vs. Passive Suspension

I've read a few comments happy to see/preferring M passive suspension, in the new M3/M4.

I was wondering the reason for this?

Wouldn't adaptive sus be preferred, since the stiffest adaptive setting would be greater than even the passive suspension?
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      09-25-2013, 10:36 AM   #2
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That's what they want you to think...
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Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."
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      09-25-2013, 10:41 AM   #3
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Honestly, some people don't like the "goldilocks" nature of adaptive suspensions. I've had them, and I get tired of switching modes. Maybe i've never had a good one.

Usually they are ruined by the softest mode needed. That mode dictates very soft springs, which then means the dampers are forced to work extra hard to control the car's motions. Usually, it's the dog's breakfast.

Possible on this car that because whatever Comfort mode won't be all that comfortable, it'll actually work.
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      09-25-2013, 10:44 AM   #4
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^I think the 3-stage adaptive on the E9x models is great. I'll be speccing adaptive again, and hope the Comfort mode is similar as the softer suspension is the fastest setting on most roads as it absorbs midcorner bumps. I just leave this car in C, unless it's a track day.

On my E60 I also loved the system, expect that was a softer setup so my day to day was Normal and, as the N mode adapted automatically, I never used C or S in that car.
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      09-26-2013, 11:33 PM   #5
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I'm a chassis engineer and I've tuned these types of suspensions on a couple cars at the OEM level. Sach's latest adaptive system on the F30's and E9X ZCP's are pretty good. The 3rd generation magneride on the ATS and C7 is comparable. A lot of the other technologies out there, including older versions of both of those, aren't that great. Too soft in comfort mode, too stiff in sport mode, and not very linear or natural feeling.


At the end of the day, any suspension technology is only as good as the guy who tunes it. A well tuned Semi-Active suspension is going to out-perform a well tuned passive system every time (considering OEM options only). I'd check the option box, no question.

Edit: Since this is now linked to in a sticky, I should make some corrections here for clarity:

1. The F30 I drove did not, in fact, have the adaptive suspension.
2. Tenneco is the supplier of the F30 adaptive system, NOT Sachs. They are different systems with different performance capabilities.

Last edited by Racer20; 04-15-2014 at 08:07 PM. Reason: Corrected some info . . .
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      09-27-2013, 08:02 AM   #6
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Racer20, do you know details of how things have evolved and improved since the Exx M cars "EDC" (which I realize was not BMW's first active suspension offering, but it is the first one that many people here are likely to be familiar with) to today's Fxx generation "DDC". Also, how do today's M and non-M implementations differ? Are there distinguished hardware systems, or is it all in the software?
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      09-27-2013, 11:39 AM   #7
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Quote:
Originally Posted by Racer20 View Post
I'm a chassis engineer and I've tuned these types of suspensions on a couple cars at the OEM level. Sach's latest adaptive system on the F30's and E9X ZCP's are pretty good. The 3rd generation magnaride on the ATS and C7 is comparable. A lot of the other technologies out there, including older versions of both of those, aren't that great. Too soft in comfort mode, too stiff in sport mode, and not very linear or natural feeling.


At the end of the day, any suspension technology is only as good as the guy who tunes it. A well tuned Semi-Active suspension is going to out-perform a well tuned passive system every time (considering OEM options only). I'd check the option box, no question.
Thanks for the info.
It's nice to hear from an engineer that's worked on these systems.

mkoesel, brings up some good questions.
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      09-27-2013, 11:49 AM   #8
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I may check the box. I quite liked the EDC in my previous E9X M3's despite rarely ever changing modes.
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      09-27-2013, 11:56 AM   #9
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I only change modes on the track. The rest of the time it is on soft mode.
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      09-27-2013, 12:29 PM   #10
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Quote:
Originally Posted by Racer20 View Post
I'm a chassis engineer and I've tuned these types of suspensions on a couple cars at the OEM level. Sach's latest adaptive system on the F30's and E9X ZCP's are pretty good. The 3rd generation magnaride on the ATS and C7 is comparable. A lot of the other technologies out there, including older versions of both of those, aren't that great. Too soft in comfort mode, too stiff in sport mode, and not very linear or natural feeling.


At the end of the day, any suspension technology is only as good as the guy who tunes it. A well tuned Semi-Active suspension is going to out-perform a well tuned passive system every time (considering OEM options only). I'd check the option box, no question.
I'm surprised you rate the F3x adaptive suspension. I think it sucks. BMW have admitted to making the Sport setting overly stiff by request of the marketing team, to ensure the owners 'feel' what they paid for. What a disastrous approach. The F30 is the first road car I have experienced 'jacking' with, and been speed limited in the 'Sport' setting.

On the other hand the M6 has a decent system. Hopefully the F8x will have something similar to this.
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      09-27-2013, 12:49 PM   #11
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Quote:
Originally Posted by Sedan_Clan View Post
I may check the box. I quite liked the EDC in my previous E9X M3's despite rarely ever changing modes.
What mode did you end up leaving it in?
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      09-27-2013, 01:01 PM   #12
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Quote:
Originally Posted by Mahlzeit View Post
What mode did you end up leaving it in?
Almost always in Sport with the Power button engaged, but occasionally in Normal. Comfort was too soft for my tastes; I prefer a stiffer ride. I was also lowered on H&R Race springs, so the differences between the modes became more apparent.
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      09-27-2013, 01:09 PM   #13
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I had DDC on my F10 and didn't like:

- Flipping to sport mode every time the car was started.
- Since the springs are passive they have to be tuned for the softest mode.
- The electric dampers were not strong enough to overcome the weak springs.
- The car felt under springed and overdamped in all modes except the softest.

Now, this might just be in my head but I would think the springs and dampers can only be tuned to work optimally with each other in one setting. With passive dampers this is what all tuning has been spent on. Making sure the springs and dampers are optimally match to each other and to the car. I'm not checking the DDC box other than if in a test drive the softest modes feel better than the passive setup.

Last edited by solstice; 09-27-2013 at 01:43 PM.
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      09-27-2013, 01:39 PM   #14
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I love having ZCP with EDC. I'm in comfort 80% of the time on the road but will use both normal or sport on the road depending on the surface conditions and how aggressive I want to be. For track its sport setting. I think there is a noticeable difference and use for all three settings. It's subtle, but all 3 have their uses.
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      09-28-2013, 01:51 PM   #15
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Quote:
Originally Posted by solstice View Post
I had DDC on my F10 and didn't like:

- Flipping to sport mode every time the car was started.
- Since the springs are passive they have to be tuned for the softest mode.
- The electric dampers were not strong enough to overcome the weak springs.
- The car felt under springed and overdamped in all modes except the softest.

Now, this might just be in my head but I would think the springs and dampers can only be tuned to work optimally with each other in one setting. With passive dampers this is what all tuning has been spent on. Making sure the springs and dampers are optimally match to each other and to the car. I'm not checking the DDC box other than if in a test drive the softest modes feel better than the passive setup.
From what I've heard from other chassis engineers who tune these types of suspensions, the F10 adaptive suspension is not tuned that well, and the new 6 series is MUCH better (edit: referring to non-M's here). The F10 was one of the first vehicles tuned under BMW's new strategy of less sport/more comfort.

Your theory is a bit off . . . There's a lot of physics and engineering behind it, but passive dampers are ALWAYS a compromise. Adaptive dampers are one step closer to being able to optimize damping for any road condition and driving behavior. It's only in the past couple years that the hardware, software, AND tuning ability of the engineers has really synched up to allow these systems to perform better than a passive set up in all conditions.

Last edited by Racer20; 09-28-2013 at 02:27 PM.
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      09-28-2013, 01:58 PM   #16
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Quote:
Originally Posted by Carlos_Danger View Post
Why would you criticize your own car so much, 1) its not a mainstream complain the f3x adaptive suspension 2) Where did you read that the marketing team requested this? seems to be off their jurisdiction, and if they did do that they wouldn't publicly comment on it 3) Have you tracked your f3x? Maybe it'll feel just right on the track the sport setting
I don't understand, should you turn off your judgement when you own something?

A magazine article revealed this after an interview with the BMW marketing team on the 4 series. If you look on the 4 series forum, you will see the article.

It will feel fine on a billard table smooth track, add bumps or ripples and you will have to back off while the comfort mode car dives past. How Sporty is that?
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      09-28-2013, 02:10 PM   #17
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Quote:
Originally Posted by mkoesel View Post
Racer20, do you know details of how things have evolved and improved since the E9x M cars "EDC" (which I realize was not BMW's first active suspension offering, but it is the first one that many people here are likely to be familiar with) to today's Fxx generation "DDC". Also, how do today's M and non-M implementations differ? Are there distinguished hardware systems, or is it all in the software?
Unfortunately I don't know the exact details of each BMW model. However, here are some things that could make the differences (Ignoring Magneride):

Hardware:
Triple tube dampers systems have a solenoid on the side that controls the damping pressure based on how much current is applied. The rebound to compression ratio (key to ride and handling performance) and min/max damping capability is determined by the passive valves in the damper, just like a normal shock.

Double solenoid triple tubes have TWO solenoids on the outside of the damper to allow separate tuning for rebound and compression. This allows faster response and more tunability.

Sachs newest system has the variable damping valve inside the shock absorber. I haven't seen one of these taken apart, but from what I understand they are very good. I would imaginee that the damping response time and hysteresis is better than an external solenoid system.

Software
One of the challenges that arises with these systems is making the car feel natural. You don't want to feel the damping changing as you're driving it, except for right when you change the modes. Tuning these systems involves a bunch of damping force maps and look up tables and "if X condition is detected, go to Y damping force table" type stuff, and getting all these different conditions and tables to blend well without jerking the car around is tough, and can be very time consuming.

Newer tuning and control software is "smarter" and some of them may have more accurate vehicle models embedded in them, and make it easier to blend these modes together with less manual tuning of complex damping force tables.

Vehicle
The more sensors you have, the more accurately the suspension ECU knows what's going on, and the better it can control the dampers. Ideally, you'd have lazer height sensors reading the ground, accelerometers on the sprung and unsprung mass at all 4 corners, a yaw sensor, and accurate GPS (In addition to steering/throttle/brake sensors) but all these sensors are expensive. So normally you get a couple accelerometers and maybe a yaw sensor. That means the system has to derive the rest of the information it needs mathematically, and the result is less accurate and increases response time.

The moral of the story is that these systems are very complex, and how it drives on one car has nothing to do with how it may drive on another. There is huge progress being made every year on this stuff, and there's really no question at this point that they ARE better than passive dampers in most respects.

Last edited by Racer20; 04-15-2014 at 08:08 PM.
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      09-28-2013, 02:14 PM   #18
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Quote:
Originally Posted by solstice View Post
I had DDC on my F10 and didn't like:

- Flipping to sport mode every time the car was started.
- Since the springs are passive they have to be tuned for the softest mode.
- The electric dampers were not strong enough to overcome the weak springs.
- The car felt under springed and overdamped in all modes except the softest.

Now, this might just be in my head but I would think the springs and dampers can only be tuned to work optimally with each other in one setting. With passive dampers this is what all tuning has been spent on. Making sure the springs and dampers are optimally match to each other and to the car. I'm not checking the DDC box other than if in a test drive the softest modes feel better than the passive setup.
Exactly.......

......the plain fact is....for a given car (sprung/unsprung mass, weight distribution, ARB stiffness, suspension design) there is ONE ideal compression and ONE rebound rate that works with a given Spring rate.

Sure you can play around with fine adjustments (and I mean fine) to suit different drivers/conditions, but even these are generally REBOUND only, and also usually want to go softer rates

So when you realise that BMW change both compression AND rebound on the F3x, and exaggerate the settings in such a way that the driver feels the big difference, that is not a well engineered solution.
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      09-28-2013, 02:16 PM   #19
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Quote:
Originally Posted by NISFAN View Post
I'm surprised you rate the F3x adaptive suspension. I think it sucks. BMW have admitted to making the Sport setting overly stiff by request of the marketing team, to ensure the owners 'feel' what they paid for. What a disastrous approach. The F30 is the first road car I have experienced 'jacking' with, and been speed limited in the 'Sport' setting.

On the other hand the M6 has a decent system. Hopefully the F8x will have something similar to this.
Making sure the customer can "feel" the difference is very important, and all OEM's have this concern. Can you explain what you mean by jacking?

Speed limiting has nothing to do with the suspension or suspension mode.

It's also important to know what version of the F30 you're referring to and what tires were on it. The one I drove exhibited good body control, felt linear and natural, and was relatively plush. The tires had some impact noise, and the electric steering poorly tuned, but those are separate issues and not a function of the adaptive suspension.
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      09-28-2013, 02:23 PM   #20
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Thanks for the reply Racer20. So like other car tech, it's evolving quickly, and they're getting it sorted pretty well. It will be interesting to see results if someone conducts an active vs. passive test for the F8x.
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      09-28-2013, 02:25 PM   #21
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Quote:
Originally Posted by NISFAN View Post
Exactly.......

......the plain fact is....for a given car (sprung/unsprung mass, weight distribution, ARB stiffness, suspension design) there is ONE ideal compression and ONE rebound rate that works with a given Spring rate.
With passive dampers, there is definitely a "sweet spot," which is what you're referring to. But, the fact is when adaptive dampers are considered, this is simply not correct.

Quote:
Originally Posted by NISFAN View Post
Sure you can play around with fine adjustments (and I mean fine) to suit different drivers/conditions, but even these are generally REBOUND only, and also usually want to go softer rates
This is also not correct. There are lots of times that you'd want to adjust compression, and lots of times you'd want to add rebound.

Dampers (even passive ones) are one of the most complex components on a vehicle. The information that is out there an available to consumers and racers (even things like the Penske tuning manual) is stuff that you learn the first day on the job as an OEM damper tuner, then throw out the next day because you realize it's kid stuff.

Unless you've tuned shocks at either the OEM level or for an F1 team, you've only got about 5% of the picture.


Quote:
Originally Posted by NISFAN View Post
So when you realise that BMW change both compression AND rebound on the F3x, and exaggerate the settings in such a way that the driver feels the big difference, that is not a well engineered solution.
I'm not sure where this quote comes from, but it's most likely BS, either as an excuse or for some other reason. I've NEVER seen marketing dictate to chassis engineers how to tune a vehicle.
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      09-28-2013, 02:26 PM   #22
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Quote:
Originally Posted by mkoesel View Post
Thanks for the reply Racer20. So like other car tech, it's evolving quickly, and they're getting it sorted pretty well. It will be interesting to see results if someone conducts an active vs. passive test for the F8x.
Exactly. Electric power steering will be the same way.
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