The coil springs only support the vehicle's weight. I truly feel that has nothing to do with it. The bounce is controlled by the shock absorber in the assembly. That is what I feel is simply no good. The only way to confirm would be to take the assembly apart and when the shock is no longer under coil spring tension, see if they move up and down easily. It shouldn't. It should require a lot of pressure to move up and down.
Note: Taking the assembly apart requires a spring compressor. Do not simply unbolt the upper strut mount. It can be very dangerous.
If you look at the pic I attached, I highlighted the shock portion of the assembly. That is the part I feel is bad.
Since they are new, I would return them and request a new set. That is the only thing that can be causing it to bounce excessively.
Let me know if I can help and what you determine.
Monday, March 14th, 2022 AT 7:36 PM