You don't say what car you have but they're generally easy to replace. I'd be surprised if they are knocking again after such a short space of time, unless they were incorrectly fitted.
It's a good idea to replace the ARB mounting bushes at the same time, especially on an older car. Fitting new ARB links/dogbones/call them what you will, suddenly creates greater movement of the ARB itself.
It's a good idea to replace the ARB mounting bushes at the same time, especially on an older car. Fitting new ARB links/dogbones/call them what you will, suddenly creates greater movement of the ARB itself.