Noises from rear suspension after lowering?

[bernard1973]

Hi

I'm wondering if anyone can help clear this up. Last year I dropped the van 30mm with H&R springs but didn't change the shocks as I'd been told the stock ones would be ok with this drop. However at low speeds there was a knocking sound from the rear so this year I've replaced the rear shocks with the shortened bilsteins from Brickwerks, but the noise is still there. Is it possible that the springs haven't been fitted correctly?
One of the rear shocks was goosed anyway so I'm not bothered about the cost of the bilsteins.

Cheers in advance

Bernard