Installed Koni FSD Struts about 5 or 6000 miles ago and now hearing a strange thud noise when going over small but sharp bumps, any bump that is say a speed bump that i take slowly, no noise, but say a small bump such as a man hole cover or crack in the road i get a thud sound from which ever corner of the car took it. i thought at first is was only the front passenger corner but its all 4 i believe, now i also replaced ALL bushings and ball joints under the car at the same time, still the stock springs though. the bounce test is fine, goes down then up to original height with no delay or extra bouncing, so i feel its something else. i also installed the powerflex bushing for control arms, maybe its that, any insight would be greatly appreciated. maybe its the cold weather idk.

 

I have pretty much the exact same setup, FSD, stock springs and powerflex bushings, etc.....

Almost 70k miles on the setup and no issues.

The powerflex bushings definitely transferred more road noise into my car, not a lot but it is noticeable.
It's a pretty solid hit when I go over manholes, potholes, seams, etc.

If you have changed tires since then, that can make a difference also.

The aftermarket rear lower control arms I had would make a very pronounced clunk any time I hit a bump when the temps were below 45 degrees.
You could even feel it in the car sometimes.
Thought it was normal until I replaced them with a good set

 

did a little investigating and I believe your right, i think its coming from the rear only now and its the original bushings on the rear control arms at 90k. i have a set of powerflex to replace them just haven't done it yet, maybe it's time i just do it. also.....my exhaust hangers are falling apart, time to replace those as well i guess, the inner rings on ALL hangers are rotted and broken, probably a source of the noise too.