So I recently purchased a EG Hatch. It was bone stock other than the exhaust. I bought new wheels, tires, and coilovers to spice it up a little bit.
I went with Tein Street Basis Z coilovers, Rota Slipstream 15x7 wheels, and Falken 195/50/15 tires.
I had a mechanic buddy install the coilovers. I took it home to install the wheels myself and I noticed he didnt lock the coilovers. I kept them at the height the mechanic left them, just raised the lower lock to the spring perch to lock them. after installing all the tires there were two major differences I noticed. First, I hear so many little rocks and pebbles hitting underneath my car as if I'm driving on gravel. My road does have loose rocks to be fair, but this wasn't present before. I'm not sure if it's due to lowering, or new wheels picking up everything, or what. There's about 1.5 inches between the lower lock collar and the bottom of the black section on my rear coilvers, and my front ones are just slightly more gapped.
Secondly, and most importantly, when I drive over some small gaps in the road there's a violent bang in the cabin. At first I thought it was the spare tire, but that's not the case. Seems to be behind the driver's side. I know people say expect the ride to be more stiff with coilovers, but I don't think this is normal. The stock ones were far better. I'm sure there's something wrong, need help diagnosing. Thanks.

 

Make sure your top caps are properly installed and there is proper shaft travel clearance before the bump stop compresses against the strut body.