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-   -   Koni FSD Review (very lengthy) (http://www.bimmerfest.com/forums/showthread.php?t=135049)

avalys 03-01-2006 09:43 PM

Koni FSD Review (very lengthy)
 
The roads here in Boston are horrendous. There's just no other way to describe them. They are mysteriously lumpy, pothole-ridden, uneven, jagged, filled with recessed seams, joints and abrupt transitions between surfaces and angles. Nearly all of the manhole covers and storm drains are at least an inch below the pavement surface: the rest are an inch above it.

BMW did a good job with the suspension on my 2003 325Ci: I never had any issues back in Connecticut. But it is hopelessly unsuited for this level of crappiness. Ever since I first came up here two years ago, every trip I've taken in and around Boston has made me wince and cringe. It's not so much the rough ride itself as the constant worry that I'm going to damage the car: driving a friend's old beater recently, it didn't bother me at all.

The highways are not so bad - it's the local roads that really suck. And it's not just the city itself - pretty much nowhere within the route 128 loop (approximately a half-circle with a twelve-mile radius) is any better. It's irritating enough that I often find myself getting on the highway and driving twenty miles to buy something that I could get within three, just to get to better pavement.

Until recently, I've just put up with this. After all, there didn't seem to be that much I could do about it: the car isn't lowered, and I have the stock seventeen-inch rims. And I certainly didn't want to compromise the handling and precision that I bought a BMW for by installing softer shocks.

Then, at the end of last summer, I read an article in Roundel about a new shock absorber that Koni has developed, that they called "Frequency-Selective Damping", or FSD. The idea is that they can respond differently to high-frequency inputs vs. low-frequency ones: there is a valve inside that sits in parallel with the rest of the oil passages, but only opens when the shock is hit fast enough with sufficient force. This means that, for high-frequency inputs (those produced by the wheel when it hits a pothole or other significant bump), it can respond softly and soak up the impact, but for low-frequency ones (produced by the movement of the car body as you brake, corner, change lanes, etc.), it can respond stiffly. So, the idea is that, theoretically at least, these shocks can improve handling and ride quality simultaneously.

This has always been at least partially possible with adjustable shocks, or systems like the Praxxis air suspension stuff. But adjustables are inconvenient - you have to decide how you want the ride before you start driving, and actually changing the settings is sometimes cumbersome. And the Praxxis system is very expensive, not to mention heavy and complicated - it requires installation of an air compressor, central control unit, and so forth. The FSDs, on the other hand, are just ordinary-looking shocks that install like any other set, and require no adjustment. They're simultaneously stiff and soft, depending on the circumstances.

Always a fan of cool engineering, I was intrigued. These sounded awesome. I did some research, and decided I'd buy a set and install them in the spring, once I had switched back to my summer tires. But sometime in January, I decided "Why wait?" and bought a set from Tirerack.

It was a bit of a risk, because I could only find one review (the one from Roundel). But I've had them on the car now for about 1000 miles, and all I can say is: they're amazing.

I was initially worried that, despite the promises, they would make the car ride like an old Buick: soft, mushy and floaty. That is definitely not the case. When I drove away from the shop that did the install, my immediate impression was that they were significantly stiffer than the stock shocks. The car feels tighter, lower to the ground (even though it isn't), and just more stable and controlled in general. The difference is especially noticeable when cornering and changing lanes - the FSDs allow a lot less initial body roll than the stock sport shocks.

But the improvements in handling are absolutely nothing compared to how these things handle bumps. For most irregularities where the pavement is unbroken (dips, rises, gentle lumps, etc.) the car still feels stiff. But anything more abrupt (usually anything that breaks the pavement - potholes, expansion joints, sudden surface elevation changes) just gets soaked up. I'd say it takes anywhere from 50% to 80% of the edge off.

It's really almost surreal, because at no point does the suspension feel soft. Yet somehow, the same bumps that used to feel and sound like driving over exploding grenades just turn into muffled thumps.

The difference is especially noticeable when driving over a patch of rough pavement that has multiple bumps and abrupt ridges in succession. There's a stretch of southbound Route 1 just north of Boston that's like that, and it's a fairly sharp curve as well (just before the Mystic River bridge, for anyone in the Boston area). Going over it before used to be miserable: I'd feel the wheels hopping around, and the rear of the car sort of squirming as they lost contact with the road and then regained it. The night after I had the FSDs installed, I drove over it, and I actually first thought that the DOT had repaired the pavement. Even in a corner, the FSDs remain stiff with respect to the motion of the car, while simultaneously handling the bumps.

These things are so good, I think I actually got a flat tire by being a little too carefree about what I drove over.

Tirerack did a test of the FSDs vs. the Koni Reds and Yellows, and the FSDs actually turned in faster lap times overall, probably because they maintain better contact with the road in corners. Best of all, they're not that expensive, at only $680 or so. Also, the shop that did the install said that the kit was excellent: well put together, fit perfectly, etc.

All in all, driving my car on these roads no longer feels like abusing it. I can't recommend these highly enough to anyone who has to travel on unpleasant pavement.

EdCT 03-01-2006 10:06 PM

Quote:

Originally Posted by avalys
It was a bit of a risk, because I could only find one review (the one from Roundel). But I've had them on the car now for about 1000 miles, and all I can say is: they're amazing.

Thanks so much for the review, I've been wanting to try these on the Z4 and yours is the first write-up I've seen outside the Roundel article.

The Z4 is very stiffly suspended, the ride's rough (especially with the run flats), but the biggest problem is how it hops and tramlines over rough surfaces.

Definitely going to put them on, thanks again.

Ed

Purpleboy 03-02-2006 07:49 PM

I've had them on for a week now together with Eibach Prokit springs. My conclusions are:

1) car corners much flatter, braking dives and acceleration lifts are reduced significantly

2) more comfortable than stock setup despite the lowering springs, you hardly feel the small, high frequency bumps

3) car seems to "stick" to the ground

4) more traction over the same corners even at much higher speeds

5) car looks really good with a lower stance

I got them cos I ordered some 19" rims and was hoping these would balance out the harshness. I'm still on 17"s now but by the feel of things, it looks like the theory is actually going to work.

As I don't track and drive in a legal fashion 98% of the time, I couldn't be any happier with the FSD's. Nothing at this price point gives you 2 seemingly opposing traits of suspension behaviour.

330ximd 03-02-2006 11:01 PM

Hi Avalys,
I am also in Boston, do you recommend them for an XI model w/out the sports suspension? These roads are making me insane, and I am also considering doing something like this maybe next year. I am hoping though that I don't see much change in suspension unless I am driving on awful roads, because I am used to the XI nonsports suspension. Anybody's thoughts are welcome, of course, thanks.

avalys 03-03-2006 01:52 AM

Quote:

Originally Posted by 330ximd
Hi Avalys,
I am also in Boston, do you recommend them for an XI model w/out the sports suspension? These roads are making me insane, and I am also considering doing something like this maybe next year. I am hoping though that I don't see much change in suspension unless I am driving on awful roads, because I am used to the XI nonsports suspension. Anybody's thoughts are welcome, of course, thanks.

I have never been in a non-sport E46, so I don't know they ride. But in short, the FSDs feel stiffer than the stock sport suspension all the time, except for the fact that they also perform very well on bad roads.

If you like the non-sport suspension, I'm not sure if you'll like the Konis. They definitely don't give you a soft ride: you get a stiff ride, just somehow, the bumps don't bother you as much.

Artslinger 03-03-2006 06:00 AM

Thanks for the excellent review.

Ace 03-03-2006 08:36 PM

Thanks for the review!! The roads here in Toronto sound similar, and I have been wondering what I can do. I might have to check these out...

Just a question for you though, did you just change the shocks? Or did you also change the springs from the OEM Sport package?

avalys 03-03-2006 09:16 PM

Quote:

Originally Posted by Ace
Thanks for the review!! The roads here in Toronto sound similar, and I have been wondering what I can do. I might have to check these out...

Just a question for you though, did you just change the shocks? Or did you also change the springs from the OEM Sport package?

No, I used the stock springs.

Koni actually says that the FSDs are only to be used with the stock springs / ride height. There are two different versions, one for the E46 with the sport package springs, and one for the E46 with the standard ones.

330ximd 03-04-2006 11:37 AM

Thanks for the feedback Avalys, excellent review as well, I'll look into it more, thanks again!

tom busby 03-05-2006 05:15 PM

Thank you for the great post.

cncmastr 03-08-2006 01:49 PM

Great review. Thanks for helping my want to spend my money...

KrisL 03-08-2006 03:27 PM

Thank you for the contribution to Bimmerfest!

KrisL 06-20-2006 02:27 PM

Avalys,

Just checking in to make sure you still have the same feelings about the FSDs. I'm thinking of picking some up for my ZHP.

Thanks,
Kris

avalys 06-21-2006 07:17 AM

If anything, my opinion has improved. It seems like they do better in the warmer weather, maybe because it affects the viscosity of the oil.

NH-SHICKS 06-21-2006 07:26 AM

I have a question. Because they effectivly reduce the high frequency bumps, do you feel you have lost any feedback or road feel?

Steve

avalys 06-21-2006 07:54 AM

Quote:

Originally Posted by NH-SHICKS
I have a question. Because they effectivly reduce the high frequency bumps, do you feel you have lost any feedback or road feel?

Steve

No. I think the mechanism is only triggered by high-frequency, high-amplitude bumps. Low-amplitude vibrations are still transmitted right through.

They feel stiffer than the stock sport suspension in every way, except they don't punish you nearly as much on heavy impacts.

andyandy 06-21-2006 04:39 PM

The streets here In Mexico are the same. Lot of wholes, storm drains lower than the rest of the road, etc

I was looking for a performance shocks, just the way you described them. Feeling soft (or kind of soft) in iregular surfaces and hard in the freeway.

Thanks for the info, I think IŽll get them:thumbup:

rruiter 06-22-2006 11:30 AM

Quote:

Originally Posted by avalys
The roads here in Boston are horrendous. There's just no other way to describe them. They are mysteriously lumpy, pothole-ridden, uneven, jagged, filled with recessed seams, joints and abrupt transitions between surfaces and angles. Nearly all of the manhole covers and storm drains are at least an inch below the pavement surface: the rest are an inch above it.

...

These things are so good, I think I actually got a flat tire by being a little too carefree about what I drove over.

Tirerack did a test of the FSDs vs. the Koni Reds and Yellows, and the FSDs actually turned in faster lap times overall, probably because they maintain better contact with the road in corners. Best of all, they're not that expensive, at only $680 or so. Also, the shop that did the install said that the kit was excellent: well put together, fit perfectly, etc.

All in all, driving my car on these roads no longer feels like abusing it. I can't recommend these highly enough to anyone who has to travel on unpleasant pavement.

Are you sure the old shocks were not worn out ? How many miles were on the old shocks ?

NH-SHICKS 06-22-2006 11:35 AM

Quote:

Originally Posted by rruiter
Are you sure the old shocks were not worn out ? How many miles were on the old shocks ?


Believe me the roads are terrible in Boston. The worst roads in AZ are better than the best in Boston.

Steve

avalys 06-22-2006 11:42 AM

Quote:

Originally Posted by rruiter
Are you sure the old shocks were not worn out ? How many miles were on the old shocks ?

Around 50,000, perhaps.

I asked the shop that installed them (Turner Motorsport) that exact question, and they said they were not worn out at all.

rruiter 06-22-2006 12:22 PM

Quote:

Originally Posted by NH-SHICKS
Believe me the roads are terrible in Boston. The worst roads in AZ are better than the best in Boston.

Steve

I know, we have great roads for me most part in Arizona. Only a couple areas where there is a lot construction have been driven to shreds but the other roads are awesome.

rruiter 06-22-2006 12:23 PM

Quote:

Originally Posted by avalys
Around 50,000, perhaps.

I asked the shop that installed them (Turner Motorsport) that exact question, and they said they were not worn out at all.

Very impressive then. Koni has always been a great manufacturer. I used to live 15 minutes away from their factory :-)

nick anderson 02-15-2007 02:35 PM

Koni FSD shocks on 1999 BMW 528iT
 
Thanks to this thread, I purchased recently a set of Koni FSD shocks that became available for the E39 5 Series wagon last year. What an improvement in ride quality! I have a 1999 528iT with the standard suspension, and Michelin MXV 4 Plus 16" tires. The standard factory suspension is substantially stiffer than that on the E39 sedan or my 1994 530iT, although not quite as bone jarring as the E39 wagon with sport suspension and low profile and/or run flat tires.

Although the handling of my E39 wagon was superb from the get go, the ride was disapointedly poor to mediocre under most road and load conditions, especially for a BMW and in comparison to my 1994 530iT wagon. This has been a common complaint from many E39 wagon owners. The only partial solution I had found previously to the poor ride was to put three 50lb bags of sand in the luggage area or load up the car with 4-5 people and luggage. I have driven several other E39 wagons so I know that this ride problem was not unique to my vehicle.

I would roughly estimate that the ride has improved (on a 10 point scale) from a 4 to a 7 (my 530iT I would rate at an 8), at the same time the handling has improved from a 7 to an 8 (my 530iT would rate a 5 or 6).

Anybody who is not happy with the strange new ride/handling balance of several other recent BMW models (Z4, X3 and X5, Mini etc) should give these Koni FSD shocks a shot. For me, it has transformed the E39 wagon driving experience and made it the finest driving experience of all the BMWs (seven) I have owned over 35 years!

Haasman 12-08-2007 10:07 PM

Koni FSD?! Questions ....a smoother ride?
 
I'm driving an 07 335i with sports suspension and it is great, I love it ... but I have noticed a bit of bobbing over rough surfaces. I would rather keep everything as stock as possible but wonder if there is something to improve the ride smoothness.

My girl has sometimes complained of feeling a bit nauseous, not from the firm ride but from the small kind of bobbing motions. I've noticed it also.

I am wondering if these other shocks would smooth the ride.

Your suggestions are appreciated,

Haasman

dynosor 12-12-2007 01:19 AM

Haasman

FSD shocks may help, but before you spend the cash try something simple:

Increase your tire pressure by 3 psi over whatever it is set to now, or at least 33/ 36 psi F/R. A stiff suspension can cause a bobbing effect on the tire sidewall if the tires are too soft. As winter has come, the shocks become stiffer and the tires softer, exaggerating this effect.

The effect is due primarily to shock friction, and will subside after the suspension is fully broken in.


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