I installed BMW 335i calipers with 380x30mm drilled and slotted rotors and Cool Carbon ST brake pads on my E89 Z4. After the last outing I went to get gas. Pulling back into garage I had low brake fluid light come on. I found left front caliper leaking fluid. Note I had not worn brake pads enough to activate wear indicator light and caliper dust boots looked fine. They weren't cooked or cracked. Needless to say I thanked my lucky stars it hadn't happened at speed the night before. To be safe I replaced both front calipers along with new brake pads and bled the brakes. I changed rear pads as long as I was doing front. Note both calipers had been on the car for maybe 3000 miles. After finishing the repair I rebuilt calipers I took off car for spares. I was shocked when I pulled the caliper seals. Both the left and right seals had pieces of rubber missing as if they had been dug out. The left seal was leaking but the right seal was ready to let go as well. The pistons looked fine with no blemishes to damage seals. See attached photos. Has anyone seen a failure like this before and if so what is cause of this failure mode. I've never seen anything like it.
Larry
Passenger side seal ready to go.
Driver side seal leaking
Larry
Passenger side seal ready to go.
Driver side seal leaking
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