I am very intrigued by the Koni FSD for my `05 MCS with stock springs - my daily driver.

I have a concern about the FSD, however, as, according to their web site, the same partno is used for the Mini One, Cooper, and S, where I would expect to see different valving for what I would expect to be different spring rates for the standard, SS, and SS+ suspensions.

Does anyone know if they do actually supply different shocks for the different models?

What am I missing about this?

 

I don't know for sure, but it is my belief that the entire MINI line uses the same struts/shocks. As far as I know, Koni only offers one set of FSDs for the MINI. What I also know is that the set of KONI FSDs I put on my MCS three weeks ago changed the "ride" from very stiff and tight feeling, to a much less jarring and stiff feeling (stock springs still used). I have yet to autocross the car (it is winter here), but in all my on-ramp and back road testing I am left feeling that the cornering capability is better than stock, with no more body lean than stock, and increased control over rough pavement. I will know more about the "performance end" of the shocks when Spring finally arrives and autocross season opens -- for now, I am very pleased.

 

Paul - I like what I've heard, but what year is your car that you are comparing? (I gather that the earlier cars were stiffer...)

When I searched http://www.realoem.com/bmw/select.do...0050300&arch=0
I find a different part for the MCS vs. MC part. From 03/02:
MCS partno for the RF Strut is 31306764919
MC RF strut partno is 31306764917

Anyone with some detailed knowledge comment?

 

The reason there is a different part number prior to 3/02 isn't due to the compression or rebound - the physical shock body is different on the early cars - different swaybar mount and top mount.

Hope that helps!
Randy

 

I read mixed messages about using the FSD's with lowering springs. Is there a negative impact on the FSD's using springs that only lower 1" or so?

Thanks!

 

that is a good question, i contacted the manufacturer and have been told that they have been manufactured for stock springs and would not be a proper applications with any lowering springs including the Koni springs. I thought about it and based on what they say, having lowering springs with FSDs defeats the purpose of the shocks. They are alternatives for the stock set up, and for lowring purposes i would direct myself towards the coilovers. However, since the product is new, we do not have a chance to get long term results from those guys that use FSDs with Eibach lowering springs in Europe. There is bunch of people on Mini2 forums doing the combination that i mentioned in last sentence. I had an idea of getting the JCW springs which will drop the car 10mms, however even at that point 10mm is not very visible, so waste of money.

 

I think some folks were trying them with Hsports too. I don't know how that turned out. I would use them with the stock springs that they are designed for.

 

Thanks, Randy, but the partnos' I posted were from after 03/20 to present, so that doesn't explain it.

As to use with lowering springs, I can't imagine lowering the car for street use anyway, as I wind up scraping on something every couple of weeks with stock springs and tires that lower the car about 4mm.

Granted that it's just the plastic "snow-scraper" that sticks down an inch scraping, but I wouldn't want to chew up the exensive parts.

I guess I'll call Koni to discuss this, as it seems odd to me that they wouldn't have different valving for the different suspensions, even if they do "fit".

 

Yeah, the SS+ and SS springs are definitely different rates, the FSD can't possibly be designed to work perfectly with both.

But then again the spring rate difference might not be big enough to matter, unlike lowering springs which could be too short and too stiff.

 

Aren't the FSDs made to change between different valving though? My guess would be that they are designed with a damping and rebound range that will work with all MINI suspensions.

 

i just read the manufacturers explanation on their website and have the same thinking with Weezer.

 

I'm don't get it - the thing that puzzles me about these shocks is that the compression rate is constant, and fairly high, while only the extension rate varies. That's what makes me wonder about the match to the different springs. Apparently it works, even when my understanding leaks.


I'm also confused about the dichotomy between compression and extension: seems to me that the variable-rate feature would work well at stuffing the wheel down into a pothole quickly, but not at all when you hit the far side of the pothole (or a bump) and the shock has to compress?

I have the same lack of understanding about Koni single-adjustable shocks - I don't understand how it can give a softer ride by adjusting only the extension damping rate, and not compression.

Can anyone steer me to a "how shock-absorbers work" link that would explain this?

 

http://auto.howstuffworks.com/car-suspension5.htm

http://www.miata.net/sport/Physics/1...-The-Road.html

Can't find links that explains EXACTLY what your question ask, but if you read those I guess maybe they'll give you a clearer picture how dampers work.

I'm not 100% sure how everything works either, but I can tell you that the Koni single adjustable dampers does work. Stiffer rebound does equal stiffer ride overall. I think it has something to do with the suspension not having as much time (and thus travel) to finish moving after a bump, therefore more forces are transmitted back to the chassis.

 

Thanks for the links.

I guess this is the key - "A typical car or light truck will have more resistance during its extension cycle than its compression cycle. With that in mind, the compression cycle controls the motion of the vehicle's unsprung weight, while extension controls the heavier, sprung weight."

Looking at a graph on the Koni site, even though it is the rebound (extension) that is adjustable, the rebound damping is always stiffer than the compression, if I'm reading it correctly.

 

Yes, most typical dampers have rebound damping thats roughly about twice as strong as compression.

Anyway, the FSD works by changing how fast the fluid inside the damper moves depending on the damping frequency. A normal damper will always have more resistance when the damper is moving fast. But this will make the ride rough/hard when you hit a hothole. By having less damping at strategic moments and more damping when you're cornering, the FSD allows better control AND more ride comfort than say, a yellow Koni (single adjustable)

 

Old Rick, you asked what year my car is....it is a 2006 MCS. On the stock suspension, it did seem to ride just about the same as the 2003 MCS that proceeded it in my garage. I don't think I would have said that there was a significant change, though. After I had the 2003 for 6 months or so, I changed to H-Sport springs and rear anti-sway bar, still using the stock shocks, which I have been led to understand is not ideal for the stock shocks. The progressive H-Sport springs did give a ride that seemed quite a bit better (to me) than the standard springs, as well as lowering the car almost an inch all around, and providing great handling on the autocross courses. I replaced the H-Sport springs and roll-bar with the stock suspension before I traded the car back in, so I was re-acquainted with the "stock ride" before I got the 2006.

Somewhere here on NAM is a reprint of an article from "Roundel", the BMW Car Club of America's magazine about the FSD shocks, albeit as used on BMWs. There is a good explanation of how the shocks sense the difference in use and adapt to various conditions. Search for the article; it is one of the things I read that helped me decide that I wanted the FSD set up on the new car. I was looking for a great ride quality without converting the MINI to a Buick, so to speak, or for making it a bone-jarring experience like I have seen with some cars equipped with stiffer than stock shocks (or like I got with 25 year old rubber cones on my classic Mini). I also wanted better control on real roads, and the benefit of increased handling when I want to autocross or take the car to track days. I did not want to lower the car, because of clearance issues that I had with the H-Sports on driveways, potholes, etc. I also added an H-Sport rear anti-sway bar just because I enjoy being able to get the rear end to come around when I need it to in autocross.

All-in-all, I am quite happy with the way the car feels right now. Once autocross season starts here, I will be able to confirm my hunch that I have lost nothing in handling, and have actually improved it. But the H-Sport springs are still in a box in the garage. When you see them in "Marketplace" on NAM, you will know I am positive I made the right choice.

Good luck with your decision,

Paul

 

Simple... they don't. Anyone who thinks they're adjusting "ride" via the **** on a Koni yellow is misinformed. (although techinically, an underdamped spring can create bouncing on rebound)

What most people atribute as "ride" I a function of spring and compression damping.

My personal belief is that there's a window of acceptable damping for any particular spring/car combination, and it's fairly small. Adjustable shocks are made to help you find that window -- not for someone to crank them back and forth from soft to firm to get "ride" and "handling".

To answer someone's questions... no, the FSD's aren't going to be "ideal" for every spring rate out there. When referring to stock springs though... the rate difference is so small as to be inconsequential. Regardless of all the nitpicking, the issue is that they're probably more ideal than the stock shocks, especially when combined with the new internal technology.

In an ideal world, every car would come with double or triple [damping] adjustable shocks, AND an owner who knew how to adjust them.

I'm not going to restate what the Koni employee told me about these shocks, because I've posted it several times before and anyone who searched would have found it... and if you searched, why not just post your question in one of those other threads rather than create a new one?

 

no, they don't

You're missing that zero aftermarket shock manufacturers product more than one shock per car model. That would be a waste of money for them. The spring rates are so close that it doesn't matter anyway.

 

While the theory might be correct, I totally disagree with your statement. I had Koni single adjustable dampers on another car and changing the rebound damping from full soft to full hard definitely has a profound effect on the ride quality.

For that perticular application, full soft was slightly too soft, allowing slightly too much "up down" motion, and full hard definitely is over damped, on bumpy corners it'll "suck" the suspension down due to over damping.

Anyway, compression damping is the main determining factor of ride comfort, and also how the car feels at corner entry, but don't think rebound damping don't change the ride harshness, it definitely does.

 

Jeff, I've read the Roundel article and the more detailed Tire Rack report that appears to be the source of the article, and every thread on Mini2 and NAM that mentions the FSD.

I'm pretty sure that no-one else has asked the question about how it works with the varieties of stock springs. I'll start another new thread if I have another new question - thanks for your comments in this one.

Thank you, Paul - great detailed info. I've ordered a set of the FSD from Mini-Madness, who matched the Tire Rack price, and who will install them for 1-1/2 hours of labor. I should have them next week, and the information I've gleaned here makes me confident that they will be just what I'm looking for.

My experience with Koni yellows on my quattro coupe mirrors psionic's, although even full soft was a way firmer ride than the stock shocks. That is why I was somewhat concerned about the FSD's working with the MCS spring rates - Koni's idea of "just right" did not match mine on the yellows.

Thanks for the help, guys.

 

OK...I'm a newbie so I'll just pass along the info...

Official line: stock springs only

Unofficial line: As long as the car does ride on the bump stops the FSD feature will function properly...1" drop *should* be OK.

Dave

 

I'm not up on the theories concerning the working of shock absorbers, but I do know that I'm glad I installed the FSDs on my '04 MCS (stock springs). I had previously swapped the run-flats for a set of Avon M-tech 550s, which made a big difference, but I got another huge improvement when I installed the FSDs. They seem to filter out the little bumps and make the car much more sure-footed in the corners, especially if the pavement is rough. I'm really looking forward to driving to the Spring Thing in Jacksonville, as well as some autocrosses and a few track days this summer.

 

The KONI FSD is a great damper that improves ride and performance. The FSD does more work in order to smooth out the ride. Unfortunately, the stock MINI has limited suspension travel which means that lowering spring may cause the FSD's to bottom out with the bump stops. When this happens, the FSD interprets the bump stops as part of the road and reacts to it - which is a false reading and produces inaccurate effects. There is also potential for damaging the FSD with repeated bottoming out.

The bottom line is that the FSD's won't work correctly with lowering springs and are designed to work with the stock springs.

 

Bound = compression

Rebound = extension

Bound is tailored to unsprung weight - for the most part since we do not want small undulations upsetting the car's balance or motions.

Rebound controls sprung weight and compressed energy from the spring. So, spring rate has, or should have, a lot to do with a damper's rebound characteristics.

Determining a spring rate is done by observing oscillation cycles for a given body with given weight proportions. There are ideal ranges that point to comfort, sporting street and race applications. If I remember, on the really sporting side a spring should ocsillate 150-180 cycles per minute. This information then tells an engineer how much control or damping force must be incorporated so that the spring AND body can be controlled. Also, it is possible to develop ten different dampers with the same damping force as measured on a dyno, but all with wildly different comfort levels. How quickly do tha damping forces need to 'ramp up' for the application should be the question.

And, bound is typically 1/3 to 2/3 rebound force.

I use to know this stuff better...terms as well.

Under damping and over damping a spring can casue either nervous or lethargic responses to roll rates.

If you want to learn more about this go to Engineering Tips.com and then go to automotive or mechanical...can't remember

 

>> I mentioned in one of the other Threads that two well known Venders have told me that the FSD's will work fine on any car as long as it is not lowered more that 1". The H-Sport Springs will work fine as they do not lower more that an inch.

>> I'm having the FSD's installed on my Mini Cooper S today and they will be mounted with H-Sport Springs. I will let you all know how it works out.


>> MINIMAX 1