I think face was noticing that the request needs more general detail like: Is it on one corner of your car, feeling any vibrations, hearing any noise, pedal feel, brake effectiveness, was dis you hear brake squeal for a time before it sparked, etc.?
I was braking aggressively but I didn't know it sparked until my friends told me. I didn't feel any vibrations. Maybe some due to ABS kicking in. Brake worked like any other time. It happened on the front XP10s with slotted roters.
jyang, get someone to take a pic of you braking at night and post it up. Of course it may not get hot enough on normal roads, so I don't want to condone anything dangerous. I have seen videos of wrx's at tracks and you can see rings of sparks inside the wheels as they brake, looks badass
Its normal. Any REAL track pad will have said sparking under heavy braking. It's quite awesome. Warning...big pic: http://www.subaruworld.net/downloads/oloa07/brakefire.jpg Small:
its not your pads sparking man, its your expensive Slotted performnce disk grinding apart and catching on fire as it leaves not only your car but your wallet at the same time. small price to pay if you wanna carry a big anchor.