Its warped front brake disks, this is the case 8 out of 10 times, its caused by repeated heavy braking without enough time for the metal to cool before the pedal is stomped on again. before you go and shell out money for new gear why dont you take your disks to a brake place and see if surfacing them will help, when i got my car it had a bad shudder under braking so i got them surfaced, and they are fine now, only took .5mm off to balance them, so the heat dispersion difference is nothing to worry about it, but you can only do this once maybe twice before you will need new disks, if more then 1.5mm gets taken off you start to affect the disks ability to disperse heat. If new disks are what you are after do NOT buy cheap weak metal ones.