Knocking sound under braking possible brake disc guard

[Richardjones74]

I've just bought 2008 Audi A4 S-Line Avant and under braking there's a small knocking sound the brakes are working fine I took it to a garage who advised that it may be the disc covers behind the disc . Has anyone had a similar problem if so please can you advise

[Magnet]

Hello Richard, 

Sorry to hear of the problem with the car. Yes, I guess it could be the disc backing plates, but the usual problem with theses with a car of that age is that they rust and may distort and the disc could then rub against this distortion. If it does, it is unlikely to result in a knocking noise - more of a constant rubbing noise. I cannot see why the garage can say it ... may be..... when they should, with examination be a able to say it is or it isn't. 

Knocking noise- do you feel any pulsating at the brake pedal when this noise occurs? 

Kind regards,

Gareth.