Strange sensation/sound on hard braking

[fishhouse4]

I have a new to me 2006 4.8is. Not sure if this is an X5 thing or just a general braking issue.

If I have to hit the brakes suddenly and very firmly - as if someone just cut me off, I have "thunk" that can be felt and heard.

After hitting the pedal quickly and hard it sounds/feels like there is a brief delay and then they suddenly grabs very hard. Almost as if something is loose maybe even. Just doesn't feel like I am used to with ABS.

Thinking its from the front for sure. Everything works as expected under light and normal braking = no clunks, sudden grabs, pulling to any side, pedal pulsing or squeaks/squeals (after I bedded in the brakes a week or so ago using Dave Zeckhausen's guide at https://www.zeckhausen.com/catalog/i...Path=6446_6443)

Not sure that makes any sense...it's hard to describe.

Anyone experienced this or have a clue what my issue might be?