Brake Shudder when pads warm up

[thefilipaneseboy]

Hey guys,

I recently went to Buttonwillow and had an issue where after about 2 to 4 hot laps my brakes would vibrate and I'd feel it through the brake pedal and steering wheel.
Stopping power wasn't affected by it, just vibration, especially during lower speeds ~40mph. The car doesn't pull to either side as well.

I've checked suspension components and brakes in case those could be the cause bit I believe I've narrowed it down to it being the brakes. Before I'd have a mix of DS1.11 pads up front with DS2500 pads in the rear with zero issue. Once I added the DS1.11s to the rear as well at Buttonwillow, the vibration happens. I bedded them in following the instructions Ferodo recommends as well so I'm not too sure what could be the cause.

Any insight would be helpful. Thank you!