Recently I've noticed a slight knock when braking. As far as I can make out it seems to be coming from behind the drivers seat and reasonably high up. It's not always apparent but there more often than not. When braking it will knock once about half way through the braking cycle, by that I mean 1-3 seconds after I press the pedal but before I stop. The car pulls up straight and there is no knocks going over bumps. I've checked the strut tower suspension nuts which seem tight. The sound to me sounds like something metal sliding and then hitting a stop. I've not had a chance yet to have a real good look. Don't know if it's relevant but I'm running MeisterR coil overs. Any one got any ideas?
2 things have caused this in the past for me :-
Unbolt the rear upper strut brace and bolt it back down again - if it was tightened with a wheel off the ground it can be trying to maintain an awkward tension between the struts and creak and clunk in worst cases.
Second, rare but it happened to me - I had a budget brand set of brake pads, which must have been badly manufactured and out of tolerance, resulting in them shifting and clunking in the carrier on braking, like you describe. I went and bought brembo's and problem solved.