Adaptive suspension vs coil overs

[jackkk]

Originally Posted by KennyPowers

no, that is not correct

these aftermarket suspensions are not active at all. they are simply systems that may have two "modes" that can be controlled electronically, using the same controls as the OEM system. so basically, imagine a "normal" and "sport" mode.

the oem adaptive systems are active systems, which are constantly adapting to road conditions and making on the fly adjustments AND have multiple modes in which they do this. they are far more advanced than the OTS systems that claim to be "electronic".

and unfortunately not, substituting the springs only will make the system perform like garbage. it would probably be a good idea to read some articles on suspension setup and geometry.

the springs are bad for three reasons. one, the OEM setup calibrates the shock length and travel length to the spring height, allowing for a specific amount of suspension travel. two, the suspension geometry and alignment are specific to a certain ride height range. three, the shocks are calibrated for a specific spring rate, which will be different than the aftermarket springs.

adding aftermarket springs on OEM shocks, or any shocks that are not shortened and re-valved to account for the new spring heights and rates is an absolutely horrible idea and will perform much worse than stock

And how about the Performance package Springs? M3 Perf. pckg has just lower spring. The same is for new M5/M6. I'm planning to go with Adaptive suspention and then switch springs tp the Perf. pckg when it will appear.

[Black Gold]

Originally Posted by jackkk

And how about the Performance package Springs? M3 Perf. pckg has just lower spring. The same is for new M5/M6. I'm planning to go with Adaptive suspention and then switch springs tp the Perf. pckg when it will appear.

the shocks are different in the ZCP package on the m3.

both need to be changed ideally. I wouldn't do it any other way

[Black Gold]

Originally Posted by Sedan_Clan

+2

Especially since a lot of race cars use Bilstein suspension components.

Toyota makes (used to) racing cars and they also make the prius and corolla

doesn't mean much. you are fooling yourself if you think some basic, and pretty cheap OEM replacement shocks have anywhere near the tech or quality of bilstein race components. its not a comparison worth making

again, in order to get a suspension that can deal with all road conditions well (ie not ride stiff / rough on regular roads or a bumpy track) you need to spend a lot of money. the money is all in the shocks.

KW v3 is not enough for my taste. substantial road comfort compromises are made, ones which make the m3 less enjoyable aroiund town, and that is not a sacrifice I would make. I would leave it stock (which I will do) or go for a proper kit with higher quality dampers.

[Sedan_Clan]

Originally Posted by KennyPowers

Toyota makes (used to) racing cars and they also make the prius and corolla

doesn't mean much. you are fooling yourself if you think some basic, and pretty cheap OEM replacement shocks have anywhere near the tech or quality of bilstein race components. its not a comparison worth making

again, in order to get a suspension that can deal with all road conditions well (ie not ride stiff / rough on regular roads or a bumpy track) you need to spend a lot of money. the money is all in the shocks.

KW v3 is not enough for my taste. substantial road comfort compromises are made, ones which make the m3 less enjoyable aroiund town, and that is not a sacrifice I would make. I would leave it stock (which I will do) or go for a proper kit with higher quality dampers.

I was referring to RACE components as I stated. Those are far from basic components.

[JoeFromPA]

Everyone knows:

1. Lower = better
2. Wheel gap = not a true racer
3. A stock suspension = never as good as what an aftermarket company can offer for $1-2.5k

....

The best blend I've ever seen on a stock sedan was an Audi RS4. The fenders bulged out OVER the tire, allowing for significant travel while visually looking both attractive and minimizing wheel gap.

However, the rear wheels at least had enormous travel for a showroom-race-car. Mind-boggling travel.

And suspension travel is an excellent thing on a tightly sprung car, as it allows the tire to be forced down into the surface even as the weight of the vehicle has been elevated.

[Sedan_Clan]

Originally Posted by JoeFromPA

Everyone knows:

1. Lower = better
2. Wheel gap = not a true racer
3. A stock suspension = never as good as what an aftermarket company can offer for $1-2.5k

You guys take this stuff beyond serious. Ever consider that people just prefer a certain look despite whether or not it causes a reduction in the overall performance of the vehicle? These are street cars after all......street cars that will spend 90% of their existence within (..or just aft of) posted speed limits.

[gee-m-w]

Originally Posted by JoeFromPA

Everyone knows:

1. Lower = better
2. Wheel gap = not a true racer
3. A stock suspension = never as good as what an aftermarket company can offer for $1-2.5k

....

The best blend I've ever seen on a stock sedan was an Audi RS4. The fenders bulged out OVER the tire, allowing for significant travel while visually looking both attractive and minimizing wheel gap.

However, the rear wheels at least had enormous travel for a showroom-race-car. Mind-boggling travel.

And suspension travel is an excellent thing on a tightly sprung car, as it allows the tire to be forced down into the surface even as the weight of the vehicle has been elevated.

Are you serious about this post and your 3 rules? None of those are remotely true.

[Sedan_Clan]

Originally Posted by gee-m-w

Are you serious about this post and your 3 rules? None of those are remotely true.

He was being sarcastic.

[Black Gold]

Originally Posted by Sedan_Clan

You guys take this stuff beyond serious. Ever consider that people just prefer a certain look despite whether or not it causes a reduction in the overall performance of the vehicle? These are street cars after all......street cars that will spend 90% of their existence within (..or just aft of) posted speed limits.

no problem at all

problem is when people belive that lowering the car with springs will "ride like stock and handle even better". that is pure BS

people are free to do whatever, but they should realize that by lowering the car with anything but the highest of quality equipment (and even then, still small compromises made) the car will be compromised. that's a fact

[signes]

Originally Posted by JoeFromPA

However, the rear wheels at least had enormous travel for a showroom-race-car. Mind-boggling travel.
.

Please tell me this was sarcasm as well...

[Joshhleee]

So oem over coils? Probably not going to track, but being able to lower your car would be nice.. Unless i replace the springs.

[IND-Distribution]

As a disclaimer:
I'm writing this off the cuff, and skipping around. This is by no means a thorough or complete document, and is meant as an overview and fuel for discussion only.

With that said, allow me to go on a bit of a rant:

There is a set amount of variables to adjust with any car, whether it is a race car or street car. Many of those variables, with respect to chassis tuning, play against each other and must be adjusted to an optimal functional medium. I might be able to make a post that will elaborate a bit on the issues suspension designers consider, to give folks an idea of what's involved in creating a good OE or aftermarket performance suspension.

Among the variables that engineers might consider, we can discuss

• geometry
• center of mass
• roll center
• spring rate
• roll stiffness
• damper valving
• compliance
• and wheel alignment

We'll leave many other factors out of the conversation, but these basics will give us quite a bit of insight into the compromises we are talking about, when discussing aftermarket coilover kits.

Many of these variables are very closely connected- changing one will compromise the other, and vice versa. Balancing these variables to create a good handling car is the art of suspension tuning.

Geometry
The term geometry typically refers to not only the base alignment of the wheels when the car is in a static position, but more importantly to the varying lengths and positions of the suspension arms.

Varying the design and lengths of the suspension arms can affect a tremendous amount of factors, but essentially the designer is chasing after just one thing- keeping as much of the tire in contact with the road as possible during all conditions- braking, acceleration, cornering, bump, and droop. There are a myriad of designs to choose from, and the benefits and drawbacks of each possible layout can create enough discussion to fill a textbook (and often does).

As we change the lengths and relative positions and mounting points of the suspension arms we can affect the sweep of the arms through space as the suspension moves through "bump" and "droop" positions (up and down, respectively). In doing so, we can determine various important characteristics of the suspension: camber curve and camber gain (the amount of camber the tire will have as the suspension moves away from it's static position, and how this camber will change progressively as the tire moves up or down inside it's wheel housing), toe curve and toe gain (the amount of toe the tire will have as the suspension moves away from it's static position, and how this toe will change progressively as the tire moves up or down in it's wheel housing).

Many other factors exist, when discussing suspension geometry itself, but we'll focus on camber and toe in this discussion. If you're interested in researching some other areas, you can read about:

• Anti squat
• Anti dive
• Bump steer
• Jacking force
• Ackerman
• Roll center migration
• Roll axis inclination

These, and literally hundreds of other factors can all be manipulated by simply changing the shape, location, and mounting positions of the suspension arms and components. Fortunately, all of these items are outside the scope of our discussion, with the exception of camber and toe.

Center of mass
Center of mass is relatively self explanatory. Each car has a center of mass, or an average point that is the midpoint between all of the masses in the car. When engineering a car, however, "mass centroid" is more relevant. Mass Centroid divides the car into many slices in the longitudinal direction, and allows us to locate the center of mass in that particular slice. This is useful because in a front engine car, for example, the engine's center of mass is much higher than the center of mass at the differential. Because most of the weight in the rear of a front engine rear drive car is located very low, the mass centroid at that particular location is also substantially lower than it is at the front of that same front engine car.

This is very useful information, and we'll relate this to roll center, later.

Roll Center
Roll center is a virtual (but very real) point, about which the car will roll as cornering force is applied. As the left and right suspension are both firmly attached to the chassis (at least ideally), when cornering force is applied one side of the suspension will compress, and one side will droop. The point about which the chassis rolls as a result is called the roll center.

It should be noted that both the front and rear suspensions have their own roll centers, which are determined by examining the respective geometries of those suspensions independently. It should also be noted that as the suspension moves, the roll center will change and "migrate", and so is only the roll center at that particular instance.

Spring Rate
Most cars are suspended by metal springs, wound into coils. Springs maintain a given ride height and geometry, while also allowing for compliance and movement of the suspension over road irregularities. Spring rate is typically measured in KG per MM, or LBS per inch, meaning that a typical spring measurement will show the amount of force necessary to compress a spring a given distance. For example, a 500lbs/in spring will compress 1 inch when a 500lbs force is applied.

It is important to note that when a spring is compressed and released, it will oscillate unless a damper is there to control it.

Roll Stiffness and Roll Moment
All this nonsense finally brings us to roll stiffness, where we can relate a few of the above factors and see how some variables interact.

Roll Moment is literally a moment, in physics terms. A roll moment is determined by obtaining a distance measurement between the (front or rear) suspension's roll center and the location of the mass centroid at that particular location. The larger the roll moment, the more the car will roll as it takes a corner.

Two notes-

• The front and rear roll moments are rarely the same.
• Roll moment will also change, as roll center migrates, as the car rolls.
• Roll moment can be manipulated by raising or lowering a car, but this will manipulate the mass centroid, roll center, and roll moment simultaneously. You can see how this can rapidly turn things into a bit of a "soup of variables", where many factors play against one another.

Roll Stiffness is the measure of the car's ability to resist roll. We typically refer to roll stiffness only as a factor of spring rate, and do not usually take the size of the roll moment into account, when making basic suspension setup decisions.

A very soft spring will not do much to resist body roll. As cornering force is applied and the roll moment does it's job, the spring will compress with relatively small forces, and your grandmother's Cadillac will rapidly raise one side of the car while wildly compressing the other, in an exciting display fit for 80s action movies.

A stiffer spring will resist these cornering forces to a greater degree, and keep your BMW M4 flat through the corners. Sway bars or anti roll bars also provide roll stiffness, and allow for a car to resist roll.

We'll get back to why this is important later.

Damper Valving
Dampers are what keep your spring from oscillating. If you've ever seen a very old car bouncing up and down on it's suspension after driving over a bump, you've seen a car with non-functional dampers. We'll discuss why this is a problem later as well.

Tuning suspension dampers is a science in itself, and good tuning requires the use of some expensive testing equipment and some very clever engineers. Fortunately the more reputable companies have the basic valving figured out for you, and leave only the fine adjustments to you. I won't discuss any more specifics of damper valving here, but we can leave it at this- entire books have been written about dampers alone.

Compliance
In order to maintain a tire's contact with the ground, a suspension must be compliant. That is to say, a suspension must adequately absorb road irregularities by allowing for the tire's movement. Compliance is typically achieved by using adequately soft spring rates, but this comes at a compromise, which I promise we will discuss soon.


And now, without further ado....

The Big Picture
The big picture is, that the job a suspension engineer is incredibly complex not simply because they must spec a car to the manufacturer's liking, but because meeting their goals involves juggling and compromising many variables that are in absolute conflict and opposition with each other.

Allow me to give you some examples-

Compliance keeps your tire in contact with the road, so compliance is good, right? This means that we should use a soft spring.

One of the negative consequences of using a very soft spring is that you cannot adequately counteract cornering forces. What you get is body roll, followed by dreaded unwanted geometry change. In simple terms, if you decided that you want 3 degrees of negative camber to keep your tire in perfect contact with the road while cornering, using a very soft spring (and the resultant body roll) will force one side of the car into very heavy compression, and one side into very heavy droop. This means, half your car has entirely too much negative camber, and half your car has nearly none! We do not have good cornering grip, and that just won't do.

So we go back to the drawing board, realizing now that unwanted geometry change is our enemy, and we use a stiff spring. We've now lost compliance, and our car's tires are skipping across road irregularities with no opportunity to absorb them! Once again, we do not have good grip.

This is just one example of the conflicting variables that suspension engineers have to deal with every day. There are literally thousands of factors to consider, nearly all of them in opposition to all the rest.


But Ilia, what is your point?
My point is as follows:

• Tuning a suspension system is a very complex undertaking indeed.
• We should not speculate on the benefits of a high ride height, soft spring rate, low ride height, or stiff spring rate untill we have compelted some analasys of the M3/M4 as delivered from BMW.
• It is not typically possible to analyze a car's performance by feel. Lap times are a half-decent indicator, telemetry data is even better.
• When designing an aftermarket performance suspension, it is important to do computer analasys, lab testing, and real-world testing to determine what combinations will yield a good result.
• Do not discount KW just yet. KW is an OE supplier for AMG (and your own BMW in the form of the KW ClubSport found on the E92 M3 GTS), and KW engineers have access to some of the most rare testing equipment in the world, along with some of the most demanding test courses- the Hockenheimring and Nurburgring. KW is one of the only suspension manufacturers in the world to have an in-house 7 post test rig, equiment that not all current F1 teams have access to. I have tremendous faith in KW to build a high quality product.
• While it is possible for a hobbyist to set up dampers by feel with no help, best results will always be found when cooperating with a trained professional who is experienced in trackside car setup. It is typically best to start with the damper manufacturer's recommended settings, especially when those settings are coupled with a suggested spring rate.
• Finally, remember that original equipment manufacturers must balance NVH, ride quality and handling. The out of the box BMW setup is of course very well designed, but typically an enthusiast that is willing to slide the scale in a different direction and make a compromise is in a position to gain some performance.

Hope that helps!

[IND-Distribution]

Oh, one more thing-

Spring rates typically work best with a given tire. Install a grippier tire, and you'll need to change your spring and damper to suit as forces acting on the car are multiplied.

So while the original spring and damper will more than likely suit the original tire nicely, upgrade your tires to sports tires or even r compounds, and it will behoove you to change your springs and dampers as well.

[Racer20]

Originally Posted by Ilia@IND

As a disclaimer:
[*]It is not typically possible to analyze a car's performance by feel. Lap times are a half-decent indicator, telemetry data is even better.

This is the only point I'll partially disagree with . . . OEM's still do quite a bit of the fine tuning by feel, especially with dampers. It's not yet possible to fine tune dampers for ride quality using objective data, and in most cases, collecting and analyzing data only slows the process down. It can take 10+ years for an engineer to become what I'd consider good at damper tuning.

The more biased towards racetrack performance a car is, the more useful a 7-post rig becomes.

[RocketBoots]

Pretty useless post. All that's common sense knowledge ever 16 yr old boy racer knows

Seriously, though, I knew it was complicated. But this is another level. Now I'm reconsidering...

Do aftermarket manufacturers, like KW, Ohlins, etc. design/test the suspensions for a specific car, in the case of "specialty" mass market sports cars, such as the M3/M4, 911, etc?? Seems like that would be the only way to do it accurately...

Also, how does adaptive or passive play into all this, for quality aftermarket suspensions??

And really, thanks for all the info.

[bmwluvr24]

Originally Posted by KennyPowers

no problem at all

problem is when people belive that lowering the car with springs will "ride like stock and handle even better". that is pure BS

people are free to do whatever, but they should realize that by lowering the car with anything but the highest of quality equipment (and even then, still small compromises made) the car will be compromised. that's a fact

I won't say anything about the car riding like stock, but the handling characteristics improved drastically with the replacement of the stock springs for H&R Sport springs. I also changed to a grippier tire with the drop. The stock ride was too floaty for my taste, so that was a relief when I tested the car after all was said and done. I do agree that people expect race car status with simple suspension mods like I have done. I thought cutting the springs was TRULY the way to go race car??

[Sedan_Clan]

Originally Posted by Ilia@IND

But Ilia, what is your point?
My point is as follows:

• Tuning a suspension system is a very complex undertaking indeed.
• We should not speculate on the benefits of a high ride height, soft spring rate, low ride height, or stiff spring rate untill we have compelted some analasys of the M3/M4 as delivered from BMW.
• It is not typically possible to analyze a car's performance by feel. Lap times are a half-decent indicator, telemetry data is even better.
• When designing an aftermarket performance suspension, it is important to do computer analasys, lab testing, and real-world testing to determine what combinations will yield a good result.
• Do not discount KW just yet. KW is an OE supplier for AMG (and your own BMW in the form of the KW ClubSport found on the E92 M3 GTS), and KW engineers have access to some of the most rare testing equipment in the world, along with some of the most demanding test courses- the Hockenheimring and Nurburgring. KW is one of the only suspension manufacturers in the world to have an in-house 7 post test rig, equiment that not all current F1 teams have access to. I have tremendous faith in KW to build a high quality product.
• While it is possible for a hobbyist to set up dampers by feel with no help, best results will always be found when cooperating with a trained professional who is experienced in trackside car setup. It is typically best to start with the damper manufacturer's recommended settings, especially when those settings are coupled with a suggested spring rate.
• Finally, remember that original equipment manufacturers must balance NVH, ride quality and handling. The out of the box BMW setup is of course very well designed, but typically an enthusiast that is willing to slide the scale in a different direction and make a compromise is in a position to gain some performance.

Hope that helps!

Thank you!!!!! This should help quiet at least some of the detractors.

[M3ryder55]

Thank u Ilia. Another reason why I love IND. Keep doing what you guys do!

[ixse]

majority of people who fiddle with suspension on vehicles like M3 (where countless hrs were spent by M division professional to set up), end up with worse dynamic vehicle. if it's worth the final esthetics (i.e lower / no wheel gap), than so be it.
I personally think F80 already comes with minimal wheel gap, and at the same time enough clearnace to cope daily driving in LA. Even with all the track times i've spent, i don't even think i can find 10/10 of this car's ability anytime soon anyway. just don't feel the need for "upgrade" in the suspension department.

[Sedan_Clan]

Originally Posted by ixse

majority of people who fiddle with suspension on vehicles like M3 (where countless hrs were spent by M division professional to set up), end up with worse dynamic vehicle. if it's worth the final esthetics (i.e lower / no wheel gap), than so be it.
I personally think F80 already comes with minimal wheel gap, and at the same time enough clearnace to cope daily driving in LA. Even with all the track times i've spent, i don't even think i can find 10/10 of this car's ability anytime soon anyway. just don't feel the need for "upgrade" in the suspension department.

To each their own though.

[IND-Distribution]

Originally Posted by RocketBoots

Pretty useless post. All that's common sense knowledge ever 16 yr old boy racer knows

Seriously, though, I knew it was complicated. But this is another level. Now I'm reconsidering...

Do aftermarket manufacturers, like KW, Ohlins, etc. design/test the suspensions for a specific car, in the case of "specialty" mass market sports cars, such as the M3/M4, 911, etc?? Seems like that would be the only way to do it accurately...

Also, how does adaptive or passive play into all this, for quality aftermarket suspensions??

And really, thanks for all the info.

KW and Ohlins test to the vehicle. KW in particular will develop the spring and damper on a car, test the car on a 7 post rig before ever driving on a race track, and then tests again at Hockenheimring and Nurburgring.

BMW used KW's Clubsport coilover on the M3 GTS, and I have a feeling BMW will continue to use KW on their higher performance models.

Originally Posted by Sedan_Clan

Thank you!!!!! This should help quiet at least some of the detractors.

Originally Posted by M3ryder55

Thank u Ilia. Another reason why I love IND. Keep doing what you guys do!

Thank you both so much for the kind words!

[aus]

Originally Posted by Ilia@IND

KW and Ohlins test to the vehicle. KW in particular will develop the spring and damper on a car, test the car on a 7 post rig before ever driving on a race track, and then tests again at Hockenheimring and Nurburgring.

BMW used KW's Clubsport coilover on the M3 GTS, and I have a feeling BMW will continue to use KW on their higher performance models.

And yet, some people think they're only worthy of a $25,000 car.

.