Adaptive vs. Passive Suspension

[NISFAN]

Originally Posted by Racer20

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.

Jacking is the term used to describe the phenomenon when the suspension, when hit with a series of bumps is unable to 're-set' it's ride height between bumps, meaning that each compression 'jacks' down the ride height. This is generally experienced on vehicles with soft spring rates and high rebound rates. F30 adaptive in Sport mode exhibits this behaviour.

My car was an F30 330D with 19" M403 wheels and Bridgestone RFT, all factory fit.

I have swapped to a passive suspension F30 and it is miles better, perfect (if still softly sprung) spring to damper rates.

F30 has a cheap ass Adaptive, which I am sure F8x won't have.

[NISFAN]

Originally Posted by Racer20

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.

So when tuning a suspension for 'road use' do you go for anything other than the 'sweet spot'? Answer is NO, we are not tuning a car to gain 10th's round a race track, and taking out understeer for turn 11, we are making life comfy for Joe Bloggs on the A543.

Originally Posted by Racer20

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.

See above, we are not talking track here.

Originally Posted by Racer20

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.

Wow, OK I guess me having years of experience tuning my own 3 way adjustable dampers on my racing car puts me in the 5% bracket. That explains why I think the F30 adaptive is a steaming pile.

Originally Posted by Racer20

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.

It was posted on this forum from a 4 series launch interview.

Comments on how poor the 4 series suspension is have been echo'd by motoring journo's including the well revered Chris Harris, maybe because he isn't an F1 driver, he also doesn't know what he is talking about?

Please note, my comments are about the F30 system, which is a standard 'cheap' F20 twin tube damper, fitted with a solenoid adjusted valve. The M6 adaptive feels much better than this system, but still get the feeling that a well tuned Monotube system would be superior.

[solstice]

No doubt the F8X will have better HW and SW but for me it doesn't change anything. Unless the softest mode is significantly better ( it needs to offset additional costs, new and replacement and reliability concerns ) for my preferences than the passive system this is one box I will not tick. It's a solution to a non existent problem since I always thought BMWs sportiest passive suspensions on the sportiest cars been superbly tuned for me.

[NISFAN]

Originally Posted by solstice

No doubt the F8X will have better HW and SW but for me it doesn't change anything. Unless the softest mode is significantly better ( it needs to offset additional costs, new and replacement and reliability concerns ) for my preferences than the passive system this is one box I will not tick. It's a solution to a non existent problem since I always thought BMWs sportiest passive suspensions on the sportiest cars been superbly tuned for me.

You are hopefully correct, the F8x programme can support a more advanced system than F3x, so would imagine both Passive and Adaptive systems will be better. Being an M car, they are also able to tune Sporty rather than comfy.

[Racer20]

Originally Posted by NISFAN

Jacking is the term used to describe the phenomenon when the suspension, when hit with a series of bumps is unable to 're-set' it's ride height between bumps, meaning that each compression 'jacks' down the ride height. This is generally experienced on vehicles with soft spring rates and high rebound rates. F30 adaptive in Sport mode exhibits this behaviour.

My car was an F30 330D with 19" M403 wheels and Bridgestone RFT, all factory fit.

I have swapped to a passive suspension F30 and it is miles better, perfect (if still softly sprung) spring to damper rates.

F30 has a cheap ass Adaptive, which I am sure F8x won't have.

I'm embarrassed to say that I just made a phone call and found out that the F30 I drove did not have the adaptive suspension option. So, with that in mind, I will retract my comment about the F30 adaptive suspension being good, as I have not driven it. Looking at your picture, I'd say you're right in that the F30 suspension is not the latest and greatest.

Your definition of jacking is also correct.

You're still wrong when it comes to the practicalities of tuning passive vs. active suspension though. A damper has two main jobs: Control the motion of the bodies mass on the springs (~1.5Hz) and control the wheel's motion due to road inputs (~10Hz). Because there are two very different masses being excited at a large range of frequencies, there's no way there can be one optimal setting for all conditions.

You seen to know quite a bit about this stuff. However, I do this for a living . . . I'm currently developing a next generation semi-active suspension for a 2018 product. I'm not saying they don't have their flaws, but right now, there is no question that, if tuned properly, they ride and handle better than a passive system.

[Racer20]

Originally Posted by NISFAN

Wow, OK I guess me having years of experience tuning my own 3 way adjustable dampers on my racing car puts me in the 5% bracket. That explains why I think the F30 adaptive is a steaming pile.

I

We've had guys come in who have spent years tuning their race car with $6000 triple adjustables, and who think they know about shocks. But when they're given a kit full of raw valve parts and told that they have to make a car ride, handle, steer, carry loads, and be safe, they realize they don't know NEARLY as much as they think they did.

These guys are fun to work with, because they tend to think that race car engineer > OEM engineer, and invariably get smacked down by their manager when they waste 3 months and the car still rides like shit. They then come back to me and I show them how we do things on the production side.

Can you tell me why dampers have hysteresis? Or how to eliminate valve noise? Calculate the gas pressure and maximum damping capacity of your shocks?

[NISFAN]

Originally Posted by Racer20

I'm embarrassed to say that I just made a phone call and found out that the F30 I drove did not have the adaptive suspension option. So, with that in mind, I will retract my comment about the F30 adaptive suspension being good, as I have not driven it. Looking at your picture, I'd say you're right in that the F30 suspension is not the latest and greatest.

Your definition of jacking is also correct.

You're still wrong when it comes to the practicalities of tuning passive vs. active suspension though. A damper has two main jobs: Control the motion of the bodies mass on the springs (~1.5Hz) and control the wheel's motion due to road inputs (~10Hz). Because there are two very different masses being excited at a large range of frequencies, there's no way there can be one optimal setting for all conditions.

You seen to know quite a bit about this stuff. However, I do this for a living . . . I'm currently developing a next generation semi-active suspension for a 2018 product. I'm not saying they don't have their flaws, but right now, there is no question that, if tuned properly, they ride and handle better than a passive system.

I'm yet to be convinced about adaptive. All the systems I have experienced have not been positive.

[solstice]

Racer20 except for the actual damping there are other just as important factors for the suspension as chassi communication and predictability. Often these are in direct contradiction with the goals of an adaptive suspension. Sometimes being as focused as an insider as yourself on perfecting the technical goals of a component you lose sight of the emotional factors that adds to excitement and feeling connected to the car. EPS is a technology that suffers from this same issue. You have great knowledgable input on the tech but what is objectively "best" is not always subjectively the best for the raw driving experience.

[NISFAN]

Originally Posted by Racer20

We've had guys come in who have spent years tuning their race car with $6000 triple adjustables, and who think they know about shocks. But when they're given a kit full of raw valve parts and told that they have to make a car ride, handle, steer, carry loads, and be safe, they realize they don't know NEARLY as much as they think they did.

These guys are fun to work with, because they tend to think that race car engineer > OEM engineer, and invariably get smacked down by their manager when they waste 3 months and the car still rides like shit. They then come back to me and I show them how we do things on the production side.

Can you tell me why dampers have hysteresis? Or how to eliminate valve noise? Calculate the gas pressure and maximum damping capacity of your shocks?

No, I am not a damper designer, and I will concede to knowing <5% in the field of damper design. (I have some contacts in the suspension dept of a large tier 1. They have some impressive kit to test damper performance including hysterisis, so have a feel for the depth of the subject ).

I could never work in OEM dampers, unless it was for Ferrari or similar. In general OEM, the task is to assemble a damper on a tight budget. Afterall, there is nothing 'sexy' to the marketing team about a damper, so the less they spend the better.

However, the 5% I am familiar with, is the use and set up of them. I also know a good set up from a poor set up, and what is fundamentally wrong with it.

[LDSM]

Originally Posted by Racer20

........


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.

Racer20, thanks for the insight.

It'll be interesting to see how BMW tunes the F8x active vs passive suspension

[Needsdecaf]

Originally Posted by solstice

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.

My thoughts mirror your own, as well as my experience with adaptive suspension (4C by Ohlins / Monroe) on my Volvo V70R. Hopefully the M car, being a performance machine, won't have such a wussie "comfort" mode and the range will work better.

I somewhat regret not getting PASM in my Cayenne because the roads in Houston simply suck ass. They are really, really bad. If I end up with an F80, I'll want to drive one with active suspension as well as passive too, to see if I can live with the passive only.

[Needsdecaf]

Originally Posted by Racer20

II'm currently developing a next generation semi-active suspension for a 2018 product. I'm not saying they don't have their flaws, but right now, there is no question that, if tuned properly, they ride and handle better than a passive system.

What's your take on Mercedes Magic Body control? Looks quite like the cats pajamas. But $$$

[Racer20]

Originally Posted by solstice

Racer20 except for the actual damping there are other just as important factors for the suspension as chassi communication and predictability. Often these are in direct contradiction with the goals of an adaptive suspension. Sometimes being as focused as an insider as yourself on perfecting the technical goals of a component you lose sight of the emotional factors that adds to excitement and feeling connected to the car. EPS is a technology that suffers from this same issue. You have great knowledgable input on the tech but what is objectively "best" is not always subjectively the best for the raw driving experience.

Believe me, I agree with you. I hated adaptive suspensions until I got a crack at playing with them on my own, because every car I had driven with them felt unnatural, not linear, and unpredictable. But with the right software and the right person tuning it, those traits are not difficult to achieve.

With a passive damper, you already have the damping rate changing as the suspension goes through its motion, because there are three different stages of valving in a passive damper. Blending those three stages smoothly so they flow into each-other without creating inconsistencies in the damping on the vehicle is one of the "black arts" of damper tuning. It's difficult, but it can be done.

The same is true for a semi-active damper. It's all about blending the different modes and tables together, and making sure that when the damping increases and decreases, it does so smoothly.

EPS is a bit of a different situation. One big problem with EPS is that OEMs use them for too many functions, like lane-keeping, torque-steer mitigation, NVH filtering, road-crown compensation, etc. All those additional functions sometimes directly interfere with driver input. Get rid of all those auxillary functions, and good EPS system should be able to come pretty close to a hydraulic system. Again, the skill of the person tuning it is a BIG factor. Bigger than you'd think.

[Racer20]

Originally Posted by Needsdecaf

What's your take on Mercedes Magic Body control? Looks quite like the cats pajamas. But $$$

It does look impressive. In reality, it's just a software improvement to ABC (as far as I can tell anyway). Additional sensors that give the already-proven hardware more information to work with. If they can integrate the algorithms properly, it should be pretty good.

I've never driven an ABC car, but I'd like to. Other OEM's and suppliers are working on similar camera-based predictive systems.

[Racer20]

Originally Posted by Needsdecaf

My thoughts mirror your own, as well as my experience with adaptive suspension (4C by Ohlins / Monroe) on my Volvo V70R. Hopefully the M car, being a performance machine, won't have such a wussie "comfort" mode and the range will work better.

I somewhat regret not getting PASM in my Cayenne because the roads in Houston simply suck ass. They are really, really bad. If I end up with an F80, I'll want to drive one with active suspension as well as passive too, to see if I can live with the passive only.

If it makes you feel any better, I've driven an 06 Cayman S with PASM . . . It's a Bilstein system, and I was less than impressed with the ride quality. It's pitchy and busy, and doesn't do a good job of keeping the car flat on bumpy roads. It's good for body roll and steering, but honestly, that's pretty easy to do with a semi-active system.

The tech has improved significantly since 06 though, so I'm sure later PASM systems are much better. I'm not sure what system the Cayenne uses, and I've never driven one.

[Racer20]

Originally Posted by NISFAN

I could never work in OEM dampers, unless it was for Ferrari or similar. In general OEM, the task is to assemble a damper on a tight budget. Afterall, there is nothing 'sexy' to the marketing team about a damper, so the less they spend the better.

This is true to an extent, but it's not as bad as you might think. These days OEM's are looking for every edge they can get. Some pretty pedestrian cars are coming out with some surprising technology these days that aren't necessary advertised as such. A few sub $30k cars have valving similar to Koni FSD, and there has been a shift back to monotubes at a couple OEM's that you'll see in products coming out over the next couple years.

Even with basic dampers, the tuning process is one of the coolest things you can do on a car. Shocks can make the difference between an unsaleable, un-driveable basket case, and the best drivers car on the road. The process of getting there is a huge challenge and very interesting.

I've worked on Mexican market B-cars, heavy duty trucks, 650hp sports cars, luxury sedans, and everything else. Other than the actual car you're driving, there's not a huge difference in the actual work you're doing.

(Going to the Nurburgring for work is a decent perk too).

[NISFAN]

Originally Posted by Racer20

This is true to an extent, but it's not as bad as you might think. These days OEM's are looking for every edge they can get. Some pretty pedestrian cars are coming out with some surprising technology these days that aren't necessary advertised as such. A few sub $30k cars have valving similar to Koni FSD, and there has been a shift back to monotubes at a couple OEM's that you'll see in products coming out over the next couple years.

Even with basic dampers, the tuning process is one of the coolest things you can do on a car. Shocks can make the difference between an unsaleable, un-driveable basket case, and the best drivers car on the road. The process of getting there is a huge challenge and very interesting.

I've worked on Mexican market B-cars, heavy duty trucks, 650hp sports cars, luxury sedans, and everything else. Other than the actual car you're driving, there's not a huge difference in the actual work you're doing.

(Going to the Nurburgring for work is a decent perk too).

Yes, being paid to lap Nurburgring (provided it is a good car you are setting up) is a fantastic perk

[Racer20]

Originally Posted by NISFAN

Yes, being paid to lap Nurburgring (provided it is a good car you are setting up) is a fantastic perk

Out of curiosity, is the name of the supplier labelled or stamped anywhere on that F30 shock in that photo?

I was under the assumption that the F30 system was supplied by Sachs, but that looks different that what I'm familiar with.

[Needsdecaf]

Originally Posted by Racer20

If it makes you feel any better, I've driven an 06 Cayman S with PASM . . . It's a Bilstein system, and I was less than impressed with the ride quality. It's pitchy and busy, and doesn't do a good job of keeping the car flat on bumpy roads. It's good for body roll and steering, but honestly, that's pretty easy to do with a semi-active system.

The tech has improved significantly since 06 though, so I'm sure later PASM systems are much better. I'm not sure what system the Cayenne uses, and I've never driven one.

The system on the Cayenne is pretty decent. The last one I drove was in DC, and it wasnt enough to sway me. However, it might have been different if I had driven it here.

And I would have gone with PASM and full Air suspension.

[Racer20]

Originally Posted by Needsdecaf

The system on the Cayenne is pretty decent. The last one I drove was in DC, and it wasnt enough to sway me. However, it might have been different if I had driven it here.

And I would have gone with PASM and full Air suspension.

Good to know.

[dreamspeed]

As your average car enthusiast who tracks occasionally (not the M3 though), I love the EDC on my E92. I have the default set to comfort and I switch it to sport for canyon runs. I do feel the springs are a bit soft but its sufficient for anything I would do on the street.

When it comes time to switch to the M3 as my track car I would just go with an aftermarket setup if necessary.

[NISFAN]

Originally Posted by Racer20

Out of curiosity, is the name of the supplier labelled or stamped anywhere on that F30 shock in that photo?

I was under the assumption that the F30 system was supplied by Sachs, but that looks different that what I'm familiar with.

No, sorry, I can't read any supplier info off the label. I don't have the car any more as I swapped for a passive suspension version. It does say (made in) Spain if that means anything?

The passive system says it was made in Poland.