The brakes still work very well but when slowing hard from high speed they rumble loudly, increasingly so as the car slows. Brembos, Godspeed grooved discs front and rear, PF-Z pads front, kevlar rear. Any thoughts?

 

any vibration on the wheel or through the seat?

 

No, nothing unusual other than the noise when braking.

 

how old are the pads and disks? when were they last changed?

 

are you getting a whirring sound as grooved discs can produce one with heavy braking from high speed, not so much slow braking from slower speeds

 

Probably pad deposits on the disc.
Do the bed in procedure that Pagid lists on their site to get rid of the deposits.

 

No, not a whirring sound, a much deeper noise than that. I'll have a look at the Pagid site re disc deposits, thanks.

 

I had exactly the same with Godspeed discs and blue pads, you need to work them hard so they get hot, as per Pagid's website:
http://www.racepads.co.uk/downloads/...ll&Bedding.pdf

 

I bought discs and pads at the same time and bedded them in as recommended by Godspeed. The noise has gradually got worse and probably as you said earlier is caused by deposits on the discs. I'll work on them and see what can be done, thanks.