Switch from Koni Active to B6?

Hi Y'all, I've gone through a bit of hell over a couple of years to get my 996.2 Cab to feel right. Suspension has been fully refreshed with OEM equivalent parts. Have thicker sway bars from and rear, and new Michellin 4S tires Also added ROW M030 springs (don't want to sit any lower than this) I went with Koni FSD's so I wouldn't feel "beat up" on rough LA streets. However, I feel like the rebound control just sucks. Feels like in a sweeping higher speed corner (not on a track), or on left/right switches, I'm bounding too much, and even little course corrections send me jiggling. Once the car takes a set, the grip from the tires is there, but it doesn't feel like the car is being held down well. Like the tires are working too hard. Would a switch to B6's make a meaningful difference? I'm 20k into the car more than it's worth at this point.... feels like most things are more new than old But I don't want to feel unsafe or like the car is not "on rails" after everything I've put in. Thoughts from the group, especially from anyone who's used both? Or even Koni Sports?

Interesting. I have nothing to contribute here except that my current plan is to put Koni Special Actives on my 996.2 cab in the next month or so. Will be watching the feedback here...

Have you considered going the coil over route? Particularly a set that will allow you to keep your M030 height while providing improved performance in the areas you feel are lacking. I understand the expense concern, the rise in expenses is never ending. Bradley

Thanks. I don't want to throw another couple grand in here. Another 1500 is enough. Though I'd read about lots of people liking FEAL coilovers. In the last 3 years, looks like prices for all of these suspension parts have doubled, due to our fantastic administration......

What do you mean by 'bounding'? Is that auto-(in)correct for bouncing? If the road surface in those sweepers is rough in the sense that there are one-sided undulations over which only the left OR right wheels travel, then the stiffer ARB's are a detriment to keep the body steady and controlled, compared to stock ARB's. (They basically put more solid-axle negative side effects into your independent suspension) Do you have the combo of M030 springs and 'bump stops'/auxiliary springs as porsche lists in their parts catalogue? You should. Personally, on a 911 cabriolet I would run stock ROW springs, aux springs and stock ARBs and Koni FSD/actives. The body of a cab is just too torsionally weak/soft to run M030 and stiffer ARBs. Instead of those parts providing the necessary compliance for good road holding it now falls to the body to do so and failing at it. If you're set on the M030 springs, replace current ARBs with stock. If you're set on removing the koni fsd, I'd go for koni sport over Bilstein B6 as they will still offer better response to expansion joints, repair patches etc while offering you the possibility to set rebound damping to your preference. And replace your ARBs with stock ones. A coup� can provide the necessary body stiffness to make M030 springs, B6 and stiffer ARBs work but it will still be only great on smooth road surfaces. As you can see, the above is free of subjective criteria (whilst still not absolute). Keep that in mind when subsequent posts read along the lines of 'B6 in my cab are great', 'go for Feals, they allow you to change ride height without changing spring preload' or 'twin-tube vs monotube, I know what I would choose'.

I'm about to put Koni Sports on my RoW car, a 2004 German C4S. The roads here are generally OK, but not always, and when you hit cobblestones, you don't want harsh suspension. Which takes us to your situation. I bet the roads in your area are too rough for your setup, both the shocks and springs and stiffer sway bars. I think you are on the right track, dial back the suspension from track-performance and back to street comfort which for most of us is more than we need. If you still have the original springs, consider going all the way back to the B4 with those. The B6 are supposedly even stiffer than Koni actives, and that would be a step in the wrong direction. Just an opinion of course

Sure, bouncing. Not enough rebound control, and then the steering and chassis feel like they want to deviate from their line. This is on a NORMAL road surface. Yes, when I changed the suspension, and switched to ROW M030 springs, I switched to the correct matching bump stops for those springs. I don't know what an AUX spring is. NEVER heard that term. I could try my stock sway bars, but I'm trying to feel more on-rails, the stock amount of roll felt too "Grand Touring" for me. I'm not switching cars (unless I go get a 718 GTS down the road), and I definitely have to have a Cab.

I have an '03 Targa, which is built on the cabriolet body. Last year I replaced the factory shocks and springs with Koni Sport Yellows and Eibach lowering springs. After forty years of racing a '69 911, I was no longer interested in the hard as a go kart suspension. The Koni Sport Yellows and Eibachs are not too much different than the factory set up. It handles well and is comfortable. I have the Koni Yellows set at full soft front and rear. It handles tar strips with the same thump thump annoyance as the factory suspension. I am satisfied.

I found an interesting thread here re: rebound damping adjustment. You may find it helpful in your scenario. From what I am reading you are feeling irregularities in the road surface throw your car of course and/or feel like your car is unsettled until it reacts. Maybe you have too much damping in either the front or the rear (or both)... so the suspension is not able to conform to changes in the surface as rapidly as it needs to / as rapidly as you want it to? Not sure, as I think if bounding or bouncing as suspension skipping over irregularities, and I think of floating as vague feeling but not skipping ... https://rennlist.com/forums/racing-a...djustment.html I hope you will discover that you only need to adjust one aspect of your suspension - either the spring rates or the damping and rebound of the shocks. I don't think the sway bars will make that much of an impact unless they are binding.

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Auxiliary spring = bump stop. Was a 4-wheel alignment done after replacing the front struts and springs? That's a must.

Not sure how the bump stops are in question here. By the time you get to them, the suspension is clearly overworked. Bump stops are there as a last resort to prevent full on, metal to metal bottoming out and contact.

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The 996 cabriolet was designed alongside the coupe and was considered exceptionally rigid at the time. The 996.2 improved on that. I don't think it is too much of a noodle to handle sport suspension. Less rigid than a coupe, yes, but not a noodle. I don't know for a fact on the 911 but I do know for a fact that modern cars use the "bump stops" as part of the progressive spring rate. And I know the 996 has various bump stop part numbers. So I think it's safe to assume that it is important to: a) make sure they're in good shape, and; 2) make sure they're the right spec for the suspension. OP, what tire pressures are you using? What wheels/tires?

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There was a Panorama article that compared the various 996 suspension options, and it contained the following bits of information: "Note the decreasing height from USA standard to RoW sport with the latter about one inch shorter than USA standard in the front and around 1.5 inches shorter in the rear." "The front bumpstops are the same for all markets and suspension configurations. There are standard as well as sport rear bumpstops all of which were measured as shown in Table 5 with the rear sport bumpstop found to be 13mm shorter than the standard version." "Notice that since the RoW M030 suspension is lower, bumpstop contact occurs with less spring compression from the static loaded position than the USA M030 suspension." ---------------- I can't find the pdf article with the graphs and images, but I remember confirming visually what was described in the previous texts. The RoW M030 suspension at static ride height is very close to engaging the bump stops, especially at the front -- if I recall correctly, around 8mm of free travel. That's easily achievable during cornering or traversing bumps.

Have you thought about replacing the lower control arms?

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I'm afraid you're misled by the term bumpstop. Hence I called them auxiliary springs, the translatiom of the term Porsche uses for them in the german parts catalogue.

I am using B6 on my 99 C2, along with turbo width 18 inch twists and wide Michelin PS4's. I am not sure of the spring rate or the sway bar thickness. However, my car is not bouncy at all and it handles very well so far for me at DE and on roads like Tail of The Dragon. It is not a magic carpet ride, but it also is not a bucking bronco. It is sporty and comfortable. Re Reading your initial post, it seems to me you may just have a mismatch between the spring rate of your M030 springs, which are supposed to be: 170 lbs/in (3.0 kg/mm) front and 260 lbs/in (4.6 kg/mm) rear (per Gemini) and your shocks. Also, the M030 lower your overall height by possibly 20mm vs stock height. It could be your shocks have to be calibrated to work with the stiffer springs. It could also be that the shorter length of the M030 springs are affecting damping as your shocks may be designed assuming a full stroke of travel is potentially going to occur during compression and rebound. I am just guessing, but M030 springs are shorter and stiffer than stock springs, and the shocks need to be designed for this. Bilstein offers a B8 shock to be used for lowered 996's. B6 is the sport shock for stock height. B4 is the stock height and non sport and stock (softer) option. So, Bilstein realizes that M030 springs need a different shock than stock. Not sure if your Koni is meant for stock height or lowered?

The reason I say I'm not sure we should be looking at the bump stops (auxiliary springs, whatever they want to call them) is that under the driving conditions the OP mentioned it doesn't sound like they would be involved. Who knows. I'm more inclined to think mismatch between springs, shocks and sway bar. FW I W,

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Turns out I misremembered... Per this post by @Jalal @ Fat Cat Motorsports , the RoW M030 front suspension is actually 6mm away from engaging the bumpstop.

I have B6's on my '02 Cab, coupled with H&R lowering springs. I think this is a nice compromise between too harsh and too bouncy. Car handles great, rides okay. Any car with a 35 sidewall is going to ride a little rougher than a 40 or above series.