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      10-22-2019, 01:09 AM   #1
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Koni Speical Active Damper Data, and My Thoughts Compared to Bilstein B6s

"You don't get what you don't ask for."

Well I asked. Specifically, I asked KoniNA for damper dynos of the Special Active/FSD dampers that have piqued the interest here. Unfortunately, I didn't get quite what I asked for, but they did give me the specs they use for performance validation. It's not many data points, but does give us a glimpse into their performance, and how it compares with Bilstein B6s.

For the F3x (all F3x) Koni offers a couple of different PNs:
8745 1378L & R: xDrive front struts
8745 1318: sDrive front struts
8245 1319: sDrive & xDrive rear shocks
8745 1356: sDrive front struts (if you're replacing an OE M-Sport strut)
8245 1357: sDrive rear shocks (if you're replacing an OE M-Sport shock, but this will also fit xDrives too)

The data I was provided were the damper forces at .13m/s and .33m/s, which in more recognizable units is 5.12in/sec and 12.99in/sec. This was a bit disappointing since there wasn't a validation point in the low-speed region (0-3in/sec), which is the region that affects how well the dampers feel like they make the car handle. Dive, squat, and cornering stability are there. The higher speed regions affect how comfortable the suspension feels over sharper and shorter features.

Front Struts (blue shaded region: low-speed, red shaded region: mid-speed, green shaded region: high-speed)


Looking at the front struts, the Koni SAs have a digressive curve, like the Bilstein B6s. Digressive means the trace curves/tapers off vs continuing in a linear fashion. This is the FSD in action, maintaining a similar compression/rebound force at a higher shock velocity as a lower one. A linear piston/shock will produce too high compression/rebound forces at high shock velocities, which prevents the damper from absorbing impacts effectively and produces a harsh ride.

Compared to the B6, the Koni SAs have lower compression force (left side of the graph) across the known range (and likely in the low-speed region too). This means they probably don't feel quite as "responsive" and "stiff," as the B6s, but should have a much more comfortable ride. On the rebound side (right side of the graph) I was a bit surprised at how similar the forces were between the SAs and B6s. The SAs have an even greater rebound bias than the B6s, which means they really make you feel "sucked down" to the road after going over suspension compressing features. Over really rough surfaces or bumps (like track curbing) the suspension won't recover as quickly so you won't have as much grip. In daily driving they're more likely to keep you in your bump stops.

One thing I found interesting is that it doesn't look like there's really any difference between the Koni SA M-Sport and Koni SA regular dampers. The mid-speed has a negligibly higher compression force, but that's it. It's possible the low-speed damping could differ a bit, but for now that's in the "unknown" region.

Rear Dampers


Looking at the rear dampers there are some more interesting contrasts between the various models plotted. The B6s maintain their digressive nature, but the SAs act more like a linear piston. Where the Koni fronts have a much more digressive curve (which should be FSD), the rears look more linear in the respective compression/rebound ranges. Additionally, there's more difference between the regular SA and M-Sport SA traces. The compression side is still identical, but the M-Sport rebound is a good bit stiffer than the regular SA (which looks close to the B6 in the mid-speed range). Given that the B6's mid and high-speed rebound forces are already overdamped for our vehicles, the SA rears are VERY overdamped. Rebound like this will keep you in your bump stops making the ride harsher. Once again, with such a large rebound bias, the suspension won't recover as quickly. The compression forces are more appropriate for our vehicles, so over single and spread out bumps the SAs should be more comfortable, but over many successive bumps (like rocky dirt roads) these will be keeping the suspension compressed.

I was really hoping the Koni SA rear shocks would have more compression force, and much less rebound bias. That would produce a comfortable and controlled ride on our platform.

Overall I think the Koni SAs are a better match in the front than the B6 for OE and most lowering springs. Neither is really ideal for the rear, although the SAs are probably better than the B6 for daily driving. For smooth surfaces, or the track, where overdamping doesn't show as many negatives, I would take the B6s over the SAs.

Last edited by FaRKle!; 10-22-2019 at 01:57 AM..
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      10-22-2019, 07:01 AM   #2
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Quote:
Originally Posted by FaRKle! View Post
"You don't get what you don't ask for."

Well I asked. Specifically, I asked KoniNA for damper dynos of the Special Active/FSD dampers that have piqued the interest here. Unfortunately, I didn't get quite what I asked for, but they did give me the specs they use for performance validation. It's not many data points, but does give us a glimpse into their performance, and how it compares with Bilstein B6s.

For the F3x (all F3x) Koni offers a couple of different PNs:
8745 1378L & R: xDrive front struts
8745 1318: sDrive front struts
8245 1319: sDrive & xDrive rear shocks
8745 1356: sDrive front struts (if you're replacing an OE M-Sport strut)
8245 1357: sDrive rear shocks (if you're replacing an OE M-Sport shock, but this will also fit xDrives too)

The data I was provided were the damper forces at .13m/s and .33m/s, which in more recognizable units is 5.12in/sec and 12.99in/sec. This was a bit disappointing since there wasn't a validation point in the low-speed region (0-3in/sec), which is the region that affects how well the dampers feel like they make the car handle. Dive, squat, and cornering stability are there. The higher speed regions affect how comfortable the suspension feels over sharper and shorter features.

Front Struts (blue shaded region: low-speed, red shaded region: mid-speed, green shaded region: high-speed)
[img]
View post on imgur.com
[/img]

Looking at the front struts, the Koni SAs have a digressive curve, like the Bilstein B6s. Digressive means the trace curves/tapers off vs continuing in a linear fashion. This is the FSD in action, maintaining a similar compression/rebound force at a higher shock velocity as a lower one. A linear piston/shock will produce too high compression/rebound forces at high shock velocities, which prevents the damper from absorbing impacts effectively and produces a harsh ride.

Compared to the B6, the Koni SAs have lower compression force (left side of the graph) across the known range (and likely in the low-speed region too). This means they probably don't feel quite as "responsive" and "stiff," as the B6s, but should have a much more comfortable ride. On the rebound side (right side of the graph) I was a bit surprised at how similar the forces were between the SAs and B6s. The SAs have an even greater rebound bias than the B6s, which means they really make you feel "sucked down" to the road after going over suspension compressing features. Over really rough surfaces or bumps (like track curbing) the suspension won't recover as quickly so you won't have as much grip. In daily driving they're more likely to keep you in your bump stops.

One thing I found interesting is that it doesn't look like there's really any difference between the Koni SA M-Sport and Koni SA regular dampers. The mid-speed has a negligibly higher compression force, but that's it. It's possible the low-speed damping could differ a bit, but for now that's in the "unknown" region.

Rear Dampers
[img]
View post on imgur.com
[/img]

Looking at the rear dampers there are some more interesting contrasts between the various models plotted. The B6s maintain their digressive nature, but the SAs act more like a linear piston. Where the Koni fronts have a much more digressive curve (which should be FSD), the rears look more linear in the respective compression/rebound ranges. Additionally, there's more difference between the regular SA and M-Sport SA traces. The compression side is still identical, but the M-Sport rebound is a good bit stiffer than the regular SA (which looks close to the B6 in the mid-speed range). Given that the B6's mid and high-speed rebound forces are already overdamped for our vehicles, the SA rears are VERY overdamped. Rebound like this will keep you in your bump stops making the ride harsher. Once again, with such a large rebound bias, the suspension won't recover as quickly. The compression forces are more appropriate for our vehicles, so over single and spread out bumps the SAs should be more comfortable, but over many successive bumps (like rocky dirt roads) these will be keeping the suspension compressed.

I was really hoping the Koni SA rear shocks would have more compression force, and much less rebound bias. That would produce a comfortable and controlled ride on our platform.

Overall I think the Koni SAs are a better match in the front than the B6 for OE and most lowering springs. Neither is really ideal for the rear, although the SAs are probably better than the B6 for daily driving. For smooth surfaces, or the track, where overdamping doesn't show as many negatives, I would take the B6s over the SAs.
Excellent write-up and analysis! Thanks!

I've got a 335ix with the Koni SA's and Eibach mild drop springs. (along with H&R sways & a Front Strut Bar)

My second choice would have been the Eibach springs and the Koni Yellow Sport Shocks. I would have chosen those over a Bilstein product since the Koni Yellows are adjustable. My overall goal was better handing but also to smooth out the harshness of the stock suspension for daily driving and especially on long trips where highway road seams were teeth rattling. I thought the adjustability would help me to dial out harshness where with the Bilsteins I'd be stuck with however they were designed and setup to be.

I'm curious if you could please speculate on the Koni SA's vs the Koni Yellow's? If you don't have any data on the Yellows, perhaps you might take a look at them sometime? Thanks again!
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      10-22-2019, 02:17 PM   #3
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Quote:
Originally Posted by johnung View Post
I'm curious if you could please speculate on the Koni SA's vs the Koni Yellow's? If you don't have any data on the Yellows, perhaps you might take a look at them sometime? Thanks again!
I don't have any data on the Koni Yellows. If someone gets that from Koni though (I'll probably look like too much of a tire kicker if I ask them right now), I can probably take a look at it and offer my thoughts.
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      10-22-2019, 02:55 PM   #4
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Quote:
Originally Posted by FaRKle! View Post
Quote:
Originally Posted by johnung View Post
I'm curious if you could please speculate on the Koni SA's vs the Koni Yellow's? If you don't have any data on the Yellows, perhaps you might take a look at them sometime? Thanks again!
I don't have any data on the Koni Yellows. If someone gets that from Koni though (I'll probably look like too much of a tire kicker if I ask them right now), I can probably take a look at it and offer my thoughts.
I know someone who I can ask. Exactly how should I phrase the question to make sure that I get the correct information?
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      10-22-2019, 07:58 PM   #5
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Quote:
Originally Posted by johnung View Post
I know someone who I can ask. Exactly how should I phrase the question to make sure that I get the correct information?
I'd just ask for the damper dynos. I don't know how many adjustments the yellows have, but you'll probably want to ask for the dynos at different settings. For example, if they have 10 adjustments, Maybe ask for dynos at positions 1, 3, 5, 7 and 9.

What was missing from the SA info I got was a data point in the low-speed region (0-3in/sec, 0-.0762m/s). If they have data there, we'd want that too.
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      10-22-2019, 09:49 PM   #6
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Quote:
Originally Posted by FaRKle! View Post
I'd just ask for the damper dynos. I don't know how many adjustments the yellows have, but you'll probably want to ask for the dynos at different settings. For example, if they have 10 adjustments, Maybe ask for dynos at positions 1, 3, 5, 7 and 9.

What was missing from the SA info I got was a data point in the low-speed region (0-3in/sec, 0-.0762m/s). If they have data there, we'd want that too.
Thanks for your response. I put in a request for the information. I will send it to you when I receive it.

In my research for the part numbers I found the attached graph from Koni concerning their Yellow Sport shocks. The FAQs say that they are shipped at the lowest softest setting. I believe that there are about 10 settings. It says to adjust them in response to the aftermarket springs and suspension installed. They said that it is rare to run them at the firmest setting.

Below is the stated difference between the Koni Special Actives and Koni Yellow Sport shocks from the Koni FAQs.
"The KONI Special (red) has been engineered to maximize the ride comfort with good handling performance for each vehicle application. The KONI Sport (yellow) typically starts at a higher initial valving baseline to give a sportier feel and work on vehicles with higher performance parts. In some instances, KONI will only offer a Special or Sport valving and not both. Some modern cars come from the factory with higher tech suspension systems and wheel/tire packages so they would move directly into the Sport range, however they are still valved to give a comfortable ride with very good handling capabilities."
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      10-26-2019, 01:39 AM   #7
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Koni Yellows

johnung took the initiative and asked Koni for data on their Sport/Yellow shocks and then sent me the data. I've added them to the plots as well as my thoughts/interpretation of what Koni said about them.

Quote:
Originally Posted by Koni
Unfortunately, dyno charts or graphs are not something that we have readily available for all shocks. What I can provide are the production spec. compression and rebound numbers the dampers are tested to during assembly. We do not have available these rates at all different speeds. These numbers are with the shocks tested in the full soft positions. The rebound damping is approximately 100% from full soft to full firm.
Koni stated that the data they provided johnung was with the yellow shocks at their softest setting. Apparently they don't test the stiffer settings for validation/quality control at the end of the production line. From the marketing plot johnung posted previously and this statement, the yellow shocks only adjust rebound, not compression. It also seems like the max rebound is 100%, or 2x that of the softest setting. That's the basis I used for the below plots.

Front


From the limited data Koni provided us, the yellows have the same compression damping as the SAs. On the rebound side the softest setting is a bit softer than the SAs, which is probably a bit better for rebound bias. Since they're adjustable, they can always be turned up to match/exceed the SAs. I wouldn't go anywhere near the max stiffness on these though. That's a huge rebound bias.

Rear


The yellows have more compression and rebound vs the standard SAs. When I looked at the SAs I thought they could probably use some more compression force, so this is a good thing the yellows have more. Compared to the "M-Sport" SA replacements, the yellows still have the increased compression, and start a bit lower on the rebound side. At their softest they don't have quite as much rebound bias.

Overall, it looks like the yellows might be a bit more ideal than the SAs, unless there's more to the SA graphs that isn't captured in the data they provided us.
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      10-27-2019, 07:36 AM   #8
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Interesting analysis !

Following up from our discussion on the thread on EDC dampers (https://f30.bimmerpost.com/forums/sh....php?t=1296041) plus various testimonies makes me think that indeed Bilstein B6s are too harsh and I was leaning towards Koni as well, with the (not so great?) loss of EDC.

I think the interest in SA lies with the dual frequency management that these graphs may not show? At least the principle of the SA makes me like them more than the yellows, although both get very good reviews in this forum.

What do you think?
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      10-27-2019, 02:18 PM   #9
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Great work, FaRKle!

Do you have any idea how B8s would graph?

Murf
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      10-28-2019, 01:09 PM   #10
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I went from stock non-sport suspension to Koni Special Actives for M sport with M sport springs. Thanks FaRKle! for the spring part numbers!

The new set up definitely feels more comfortable than the stock set up. At low driving speeds, the car contours the road very well and feels planted. At these speeds the car feels stiffer. At higher speeds, the shocks seem to suck up bumps and it is very comfortable but the car doesn't feel as responsive to the road bumps. Large bumps will be very stiff and unsettle the car - possibly riding the bumpstops on these. The car never feels floaty or disconnected - the Koni shocks seem to level out the bumps with a softer compression and keep contact with the road with a fast rebound. The stock shocks would feel floaty over a series of bumps - it is stiff on initial compression and rebounds slowly.

I can see how some people don't like it as it feels "softer" over bumps and doesn't feel responsive and sporty compared to Bilstein which typically are stiff on compression. For me, it feels great in every day driving as it's more comfortable than the stock shocks while feeling more planted than the stock shocks.
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      10-28-2019, 04:33 PM   #11
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Quote:
Originally Posted by Lancelot View Post
Interesting analysis !

Following up from our discussion on the thread on EDC dampers (https://f30.bimmerpost.com/forums/sh....php?t=1296041) plus various testimonies makes me think that indeed Bilstein B6s are too harsh and I was leaning towards Koni as well, with the (not so great?) loss of EDC.

I think the interest in SA lies with the dual frequency management that these graphs may not show? At least the principle of the SA makes me like them more than the yellows, although both get very good reviews in this forum.

What do you think?
I'm still a little unsure about what FSD entails in its entirety. Most of the marketing statements (including the McLaren racing ones), and even video of the piston movement simulation really only make it seem like FSD is producing a digressive damping curve, and that there isn't really much to the whole frequency aspect of it. Shorter and sharper features typically fall in the high speed damping range, so it can easily just be marketing jargon/renaming.

I've only ever seen one marketing brochure that separated high speed damping and frequency statements, however, even then it wasn't very clear. Until I see some data, I'm assuming the damping forces behave the same whether you hit a single high speed damping road feature, or hit multiple of them in fast succession (not including hysteresis effects).

As to which ones to pick between SA and Yellow, well that will come down to how the damping forces, and ultimately damping ratio come out to when calculated as a whole with your corner weights and spring rates.


Quote:
Originally Posted by Littlebear View Post
Great work, FaRKle!

Do you have any idea how B8s would graph?

Murf
I'm pretty confident the B8s will have the same damping curves as the B6s. Given how over damped the B6s are, it wouldn't make sense to over dampen further.
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      11-05-2019, 03:08 PM   #12
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FaRKle! do you have any idea where the stock EDC dampers would be on this graph?
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      11-05-2019, 03:14 PM   #13
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Quote:
Originally Posted by Lancelot View Post
FaRKle! do you have any idea where the stock EDC dampers would be on this graph?
I only have dyno plots of my OE EDC dampers in full stiff mode (not powered). In reality they don't normally operate near that profile. Additionally the dampening curve rotates as the valve is adjusted. Not sure how helpful that'd be since we don't know what the "in actual operation" curves look like.

In the unpowered state with stock spring rates (or slightly higher like F80 non-ZCP) it was very stiff and harsh! With F80 ZCP spring rates it's not too bad (some might even call it an upgrade), but still a bit overdamped. In daily driving the control of overdamping feels nice, however, when pushed you start to notice the loss of grip.
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      11-05-2019, 10:08 PM   #14
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Quote:
Originally Posted by FaRKle! View Post
Koni Yellows

johnung took the initiative and asked Koni for data on their Sport/Yellow shocks and then sent me the data. I've added them to the plots as well as my thoughts/interpretation of what Koni said about them.

Quote:
Originally Posted by Koni
Unfortunately, dyno charts or graphs are not something that we have readily available for all shocks. What I can provide are the production spec. compression and rebound numbers the dampers are tested to during assembly. We do not have available these rates at all different speeds. These numbers are with the shocks tested in the full soft positions. The rebound damping is approximately 100% from full soft to full firm.
Koni stated that the data they provided johnung was with the yellow shocks at their softest setting. Apparently they don't test the stiffer settings for validation/quality control at the end of the production line. From the marketing plot johnung posted previously and this statement, the yellow shocks only adjust rebound, not compression. It also seems like the max rebound is 100%, or 2x that of the softest setting. That's the basis I used for the below plots.

Front


From the limited data Koni provided us, the yellows have the same compression damping as the SAs. On the rebound side the softest setting is a bit softer than the SAs, which is probably a bit better for rebound bias. Since they're adjustable, they can always be turned up to match/exceed the SAs. I wouldn't go anywhere near the max stiffness on these though. That's a huge rebound bias.

Rear


The yellows have more compression and rebound vs the standard SAs. When I looked at the SAs I thought they could probably use some more compression force, so this is a good thing the yellows have more. Compared to the "M-Sport" SA replacements, the yellows still have the increased compression, and start a bit lower on the rebound side. At their softest they don't have quite as much rebound bias.

Overall, it looks like the yellows might be a bit more ideal than the SAs, unless there's more to the SA graphs that isn't captured in the data they provided us.
After reading this thread a few times your last paragraph struck me:

"Overall, it looks like the [rear] yellows might be a bit more ideal than the [rear] SAs, unless there's more to the SA graphs that isn't captured in the data they provided us."

Makes me think a bit. Are you saying that for our platform an ideal mix may be Koni SA's on the front and the adjustable Koni Sport Yellows on the rear?

I just remembered a suspension conversation I had with Dinan almost two years ago when I first got a BMW. We talked about Dinan 3/4" drop springs for the Xdrive. Dinan made a big deal about using Koni Sport Yellows on the front but these were custom damped to Dinan specs. I kept assuming that they were also using the Koni Sport Yellows for the rear also. But Dinan said no, we think the stock rear shocks are fine so we leave them. Still surprises me.
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      11-05-2019, 10:28 PM   #15
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Quote:
Originally Posted by Lancelot View Post
FaRKle! do you have any idea where the stock EDC dampers would be on this graph?
I added my OE EDC dampers to the plots (unpowered state).

Front Dampers


Rear Dampers
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      11-05-2019, 10:33 PM   #16
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Quote:
Originally Posted by johnung View Post
After reading this thread a few times your last paragraph struck me:

"Overall, it looks like the [rear] yellows might be a bit more ideal than the [rear] SAs, unless there's more to the SA graphs that isn't captured in the data they provided us."

Makes me think a bit. Are you saying that for our platform an ideal mix may be Koni SA's on the front and the adjustable Koni Sport Yellows on the rear?

I just remembered a suspension conversation I had with Dinan almost two years ago when I first got a BMW. We talked about Dinan 3/4" drop springs for the Xdrive. Dinan made a big deal about using Koni Sport Yellows on the front but these were custom damped to Dinan specs. I kept assuming that they were also using the Koni Sport Yellows for the rear also. But Dinan said no, we think the stock rear shocks are fine so we leave them. Still surprises me.
I meant "more ideal" in the sense that they have higher compression and lower rebound than the SAs. From my experience they'll probably pair better with our platform due to this, however, it might still not be optimal depending on your vehicle weight and spring rates (still need to do critical damping calculations to see).
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      11-10-2019, 05:05 PM   #17
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Good thread. I ended up with the Koni SA after finding out the B6's were backordered several months. They've been great with stock xdrive springs. Pretty much what I expected the car to be from the factory.

Since I did rear shocks first and then front struts a few weeks after, I don't know what the car would have felt like with just the front struts though. I might have tried it out if I'd have seen this thread first, but I'm happy with the setup. No more floating, body roll cut in half. I do kind of find it hard to believe the stock rear shocks could be adequate with how easy they were to compress (by hand) and how incredibly long it takes for them to rebound.
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      11-10-2019, 06:51 PM   #18
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Quote:
Originally Posted by ouengineer View Post
Good thread. I ended up with the Koni SA after finding out the B6's were backordered several months. They've been great with stock xdrive springs. Pretty much what I expected the car to be from the factory.

Since I did rear shocks first and then front struts a few weeks after, I don't know what the car would have felt like with just the front struts though. I might have tried it out if I'd have seen this thread first, but I'm happy with the setup. No more floating, body roll cut in half. I do kind of find it hard to believe the stock rear shocks could be adequate with how easy they were to compress (by hand) and how incredibly long it takes for them to rebound.
My experience as well. Except I didn't consider the B6 first. With the way the rear felt stock, I can't imagine not doing them.
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      11-16-2019, 09:32 AM   #19
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Are we saying the koni SA are more comfortable/absorb small imperfections better?

I do primarily motorway driving
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      01-06-2020, 12:05 AM   #20
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Im also wondering whats the verdict? I need struts for my F30 thats stock with S704A springs.. Im stuck between Bilstein B4 / B6 or Koni SA's
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      01-19-2020, 03:16 AM   #21
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Quick feedback, i had decided on Koni SA but Koni advised against it on lowering springs and recommended Koni sport, which makes sense.

i'm settling for that, will report back in a couple of weeks when they are installed.
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