TTAC Commentator 1500cc writes:
I have an odd problem with the brakes on my 2014 Cadillac ATS 2.0 AWD. It has 35k miles on the clock and the Brembo brakes up front. It started happening last spring: when I’d apply the brakes I’d feel (more so than hear) a grinding or gritty feeling through the brake pedal. The odd part was that the brakes were nice and smooth when cold, and only started to act up after I drove a little bit and the brakes warmed up. Also, it only seemed to do this in the final few feet of a stop, say from 10 mph down to zero (or maybe I just couldn’t detect it at higher speeds). The grinding was proportionate to how hard I pressed on the pedal, but pulsed a bit with the rotation of the wheels as if the rotors were warped.
So the first thing I did was pull the front wheels (for some reason it felt like it was coming from the front) and while the rotors were good and rusty, there was lots of meat left on both the rotors and pads. But just to be sure, I installed new front rotors and pads (a shop said the rotors were too gnarly to turn). Didn’t help. Okay, let’s look at the rears, then. They actually were worn to the point of needing replacement, so on went new pads and rotors there, too. But the problem is unchanged, including the pulsing sensation.
Searching the internet, I’ve seen a few forum threads with pretty much the exact symptoms (fine when cold, grindy/gritty when warm) on everything from Explorers to pickups to Porsches. Unfortunately I couldn’t find one thread that actually had the answer. There were some left-field suggestions like an overfilled master cylinder (I took an ounce or so out of mine just to be sure), but nothing fixed it. What could it be?