Recently replaced my 2011 Justa R55 Clubman's stock shocks with Koni FSDs at 83K miles. I used the stock springs as that's what's recommended with these Koni FSDs. Did all the work myself over 2 days on the weekend.

Opinion:
Well rounded shocks great for daily drivers but wouldn't use them consistently for track or auto-x usage. They are too soft and would wear out too quickly for what you push the cars to do closer to 10/10ths driving. They are very smooth on transitions and when loaded, have a very flat/neutral response even when there are mid-transition undulations or bumps. Gives 80% of the driver control a Koni Yellow near the 10/10ths limit would get. 50% upgrade over the stock Clubman shocks, plus you're really paying for the refinement of the damping and response; translates to better driver control & comfort.
For context, this is my first experience with the FSDs but have had 5 pairs of Koni Yellow/Sport on different cars [E46 ZHP (stock sport springs), AW11 N/A (stock & ST springs) & SC (ST springs), Miata NA & NC (stock springs)]. Highly recommended as a daily driver setup + occasional track & auto-x days (2-3 sessions a year).

Bought the parts from:
- Koni FSDs 2100-4099 = Import Replacement Parts
- Lemforder Upper Shock Mount 31306772749 (2 qty)= AutohausAZ
- Lemforder Upper Shock Bushings LF-33526754123/LF-33526754124= AutohausAZ

Installation:
Overall, a pretty standard shock removal and installation process. Split it up between 2 days over the weekend.

Worked on the back shocks first which took about 3 hours all together. Included replacement, spring compression, transfer of all the suspension parts for re-assembly- bump stop, spring, shock cover, new Shock Bushings, etc..., then re-installation back on the car.

Worked on the front shocks the next day which was another 3 hours. Included replacement, spring compression, transfer of all the suspension parts for re-assembly- bump stop, spring, shock cover, new upper shock mount, etc..., then re-installation back on the car.

Pros:
- Neutral loaded response, makes the car feel very flat when you're into a corner when the shocks are loaded.
- Smoother response with big, medium and high frequency bumps, doesn't give you the jolting feeling that the stock shocks would do. Plus the damping is more responsive especially with un-even (hitting 1 side or section of the suspension) and unbalanced (different hit rates at different corners; usually due to different road conditions) situations.
- Braking response is great, no dive (in normal situations, see Cons), similar to the stock suspension; however, the FSDs are better when braking plus taking suspension hits. Stock suspension would give you an unsettling spine inducing pain upon the hit. With the FSDs it's just a slight vibration w/o the pain.
- Body roll is minimal with transitions causing the most if not the slightest amount when pushed closer to 10/10ths limit. Especially noticeable with back and forth transitions or high speed sweepers.

Cons:
- Low speed/high torque acceleration (slow roll the car then floor the gas) causes a softer response which makes the car feel like it's not valving the suspension to stiffen up. So you can feel the car tend to dig into the suspension before the hydraulic fluid builds up to stiffen the rear suspension to put the wheels torque to the ground. It could just be how the FSD is designed.
- Low speed/high torque braking, similar to the issue above, driving slow then hard braking causes the nose to dive a little more than the stock suspension. This may be due to the FSD's design but it does stiffen up the suspension when the load from the full weight of the car is applied.

It's been a great upgrade and hope this helps others decide between the stock, Bilstein, Koni FSDs, Koni Yellows on their next suspension upgrades.

 

I've had mine on for 18 months. Takes a few weeks to get full feel.

I enjoy them more that my MINI sport on my 2009 S

 

I have them on my r53 with jcw springs, I have been winning autocross's with them, currently leading STX with the local club.

I have blown the fronts though, they don't really dampen much now and bottom out easy. Yellows going in next week

 

Just curious why your not replacing the fronts with another set of FSD's?
Are you planning to lower your car and get springs this time since FSD need to be with the OEM spring.

 

because they blew out and they only have 10k miles on them

 

I should correct that, they may not be blown no leaks but they do not have enough high speed damping and I bottom out all the time, like where there's changes in pavement level from construction those types of hits bottom HARD it's friggin scary

 

The FSD have a lifetime warranty I thought (?)

However, the JCW springs are considered lowered springs and void the warranty.

 

FSDs are definitely not designed with lowering springs or heavy duty cycles for auto-x and track use; it's just how they are designed.

I talked with Sheik at Fat Cat Motorsports about it and he recommended Yellows or re-valved Bilsteins if you're serious about constant track days and auto-x.

If I went that route, I'd just get another NC or ND Miata then mod that car. It will be way more competitive.

@mega72, you won't regret going with the Yellows however keep an eye every year for leaks with heavy duty cycles. Best part is that Koni could rebuild em for a reasonable price. They can also re-valve them for both rebound and compression (2-way); stock is 1 way adjustment only, compression.

 

With the scca class changes the JCW with yellows will probably just be a daily and the track car will run smf, it has coilovers

 

I bought an R55 a few months ago, and I'm glad to find this post. I read the Koni struts are a little pricey but a big improvement. That's one of the things I noticed, potholes I never had to avoid before are met with a bone-jarring jolt. I know the dealer said one of the strut tops is cracked, but I think the problem has to be the stock struts. I'm not a mechanic, and don't really have any experience with cars and I have to do a lot of research before I spend money on expensive parts.

I'm def looking forward to upgrading the struts hopefully next year when I have the funds
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