Koni Special Actives installed. Smooth but crashy?

[IamFODI]

Installed Koni Special Actives on my new-to-me 2012 5. Kept the springs, which I'm pretty sure are stock. New strut mounts & shock mounts. New bump stops in the rear because the originals were disintegrating. Front bump stops seemed okay so I kept them (though my opinion of what seems okay might not be worth much).

The ride and handling are excellent for this kind of car, with one exception: it kind of crashes a bit over big bumps. It's not hideously unpleasant; just harder than it feels like it should be. Very out-of-character vs. the rest of the ride quality. A member of our extended family has a 2010 5 on Bilstein B4s and said ours feels crashier on big bumps.

Front LCA bushings seemed okay but could be original for all I know. Same with the ARB bushings. The tires are no-name specials that I plan to replace soon. Any chance any of those could be contributing to the problem? Or is this crashiness a known characteristic of Koni Special Actives?

 

[Silentnoise713]

Had to google Specials Actives but they seem to be renamed/repackaged FSD, likely retuned. B4 pair very well with OE springs (I have them). *Guessing* the stock springs may not match (too soft?) the Special Actives?

Do you have any intentions of lowering/stiffer spring? If so, you may be happier with B6s (inverted mono tube) for V50 (need a add a few washers (or find wider bushings) to fill some space on the trail arm mounting bolt).

 

[IamFODI]

Had to google Specials Actives but they seem to be renamed/repackaged FSD. B4 pair very well with OE springs (I have them). *Guessing* the stock springs may not match (too soft?) the Special Actives?

Do you have any intentions of lowering/stiffer spring? If so, you may be happier with B6s (inverted mono tube) for V50 (need a add a few shims to fill some space on the trail arm bolt).

Yep, Special Active is the new name for FSD.

Probability of switching to a different damper is basically zero at this point. Don't want to duplicate the expense and time. Also don't want to lower the car at all. In theory I might be interested in stiffer springs that keep the same ride height, if that even exists...

Special Actives aren't designed specifically for lowering springs AFAIK, so there shouldn't be a problem in that respect.

If this is just how life is with Special Actives, I'll just have to live with it for a while. The car rides brilliantly aside from that one flaw. What I want to do now is see what else I can do short of changing dampers again.

 

[IamFODI]

Spoke with someone at Koni. Hard to communicate experiences like this over the phone, so take the following with a grain of salt.

Based on our conversation, this might just be how Special Actives are: relatively loud/harsh on the biggest bumps, excellent everywhere else. He pointed out that the FSD mechanism kicks in only on rebound and doesn't affect compression damping at all. So, it ought to take the initial hit about as well as stock, but rebound will be much faster because of the "blow-off" effect of the FSD. Maybe that's what I'm feeling.

I floated the idea of a longer bump stop so that it would engage sooner but ramp more gradually, thinking that might mitigate the harshness of hitting the bump stops. He said a longer bump stop could easily make things worse; hitting the bump stop is a high frequency event, so it'd result in more undamped rebound.

Let's see what happens once my new FCABs, front ARB hardware, and tires get installed.

 

[Silentnoise713]

Spoke with someone at Koni. Hard to communicate experiences like this over the phone, so take the following with a grain of salt.

Based on our conversation, this might just be how Special Actives are: relatively loud/harsh on the biggest bumps, excellent everywhere else. He pointed out that the FSD mechanism kicks in only on rebound and doesn't affect compression damping at all. So, it ought to take the initial hit about as well as stock, but rebound will be much faster because of the "blow-off" effect of the FSD. Maybe that's what I'm feeling.

I floated the idea of a longer bump stop so that it would engage sooner but ramp more gradually, thinking that might mitigate the harshness of hitting the bump stops. He said a longer bump stop could easily make things worse; hitting the bump stop is a high frequency event, so it'd result in more undamped rebound.

Let's see what happens once my new FCABs, front ARB hardware, and tires get installed.

Sounds like it is behaving as it should. Pothole dodging is a way of life/sport!


This confirms the feedback from GRM.

The way they work is that they have a second set of bypass valves in them that open up when the dampers compress or rebound short distances. So when you drive over small roadway imperfections and tiny bumps, the fluid goes through the bypass and the dampers don't really provide much damping force. This makes it feel like you have the dampers set softer than they actually are, making for a more comfortable ride. When you corner hard or hit a big bump, the bypass valve slams shut and they act like a stiffer shock.

Koni special active shocks? Worth something?

Koni special active shocks? Worth something?

grassrootsmotorsports.com

 

[IamFODI]

Sounds like it is behaving as it should. Pothole dodging is a way of life/sport!


This confirms the feedback from GRM.

Koni special active shocks? Worth something?

Koni special active shocks? Worth something?

grassrootsmotorsports.com

Interesting.

Not sure that post is 100% accurate. The poster says FSD activates on compression as well as rebound; Koni told me rebound only. Also, big bumps tend to be high-frequency events – exactly what FSD is supposed to excel at....

However, that thread led me to another one: Talk to me about Koni dampers

Special Active... has a weak point in that it tends to hit the bumpstops hard if you're at all limited on travel. I did some comparison driving in a Mustang at the SEMA show and we did get into the stops hard a couple of times. Felt good overall ... Just be aware.

This sounds exactly like what I'm experiencing!

 

[Silentnoise713]

Keith Tanner's advice is always golden. He is the founder/race car enthusiasts of Flyinmiata.com and wrote a few books on performance.


I read/understand the conclusion to be the same; Koni Special Actives seem to be working as designed. If you want to dig further or see if you can optimize your setup, I suggest reaching out to Automotive Suspension Artisans | The Home of Ride Harmony | Fat Cat Motorsports, Inc.. The founder/owner, Shaikh has some great advance educational videos https://www.youtube.com/user/SuspensionTruth/videos. They are really cool to talk to and first 15 min is free just to get your though/concern out there.

 

[IamFODI]

Installed new front LCAs, ARB bushings, and ARB end links. Massive improvement in the crashiness. Still seems to hit the bump stops unusually strongly but the event is a lot less unpleasant.

Only thing I have yet to try is fresh bump stops. Might be slow on that as I'm not super tempted to rip apart the front struts again, especially when the ride is good enough overall that I'm not terribly bothered. I'm not even sure it's worse than stock at this point. Will have to compare to another 5 on different dampers at some point...

 

[Silentnoise713]

Only thing I have yet to try is fresh bump stops. Might be slow on that as I'm not super tempted to rip apart the front struts again, especially when the ride is good enough overall that I'm not terribly bothered. I'm not even sure it's worse than stock at this point. Will have to compare to another 5 on different dampers at some point...

IIRC, Shaikh@FatCat started out making custom bump stops that pair for specific models. He has a shorter/progress bump stop specially for FSD with stock springs on Mz3/MS3 (Mz5 front would be a close match).

https://fatcatmotorsports.com/FCM_Koni_products_MS3.htm

Over the years, they've become somewhat of a bespoke ($$$) suspension design shop. They seem to have left the retail side to a partner, which actually sells these for cheaper

5X Racing Mazdaspeed 3 Bump Stop Kit

5X Racing Mazdaspeed 3 Bump Stop Kit

5xracing.com

 

[IamFODI]

IIRC, Sheik@FatCat started out making custom bump stops that pair for specific models. He has a shorter/progress bump stop specially for FSD with stock springs on Mz3/MS3 (Mz5 front would be a close match).

https://fatcatmotorsports.com/FCM_Koni_products_MS3.htm.

Over the years, they've become somewhat of a bespoke ($$$) suspension design shop. They seem to have left the retail side to a partner, which actually sells these for cheaper

5X Racing Mazdaspeed 3 Bump Stop Kit

5X Racing Mazdaspeed 3 Bump Stop Kit

5xracing.com

Oh wow. Now THAT looks promising.

I'm familiar with Shaikh and his offerings. Had a great convo with him once and almost went with a Stage 3 kit for my E90 M3. Friends of mine have used his stuff and taken his advice to great effect.

Might have to try this out. Thanks!