I made the recent discovery that cleaning sticky pistons is often what is needed to solve spongy lever feel, rather than a bleed. In the past, I had bled brakes with little improvement to lever feel, and I suspect sticky pistons were the issue.
Another important tip is to balance the pistons when the pistons advance with pads and rotors in. If one piston is advancing too quickly, use a small flathead screwdriver to push the piston back in (with the wheel and pads installed) to allow the other pistons to catch up.
I’ve also stopped lubing pistons with brake fluid; there is too much risk of contaminating the pads. The pistons get lubricated by the fluid in the system. Repeating the process of extending pistons, cleaning then pushing them back in several times seems to do the trick.
March 12, 2021, 9:25 a.m. - DMVancouver
I made the recent discovery that cleaning sticky pistons is often what is needed to solve spongy lever feel, rather than a bleed. In the past, I had bled brakes with little improvement to lever feel, and I suspect sticky pistons were the issue. Another important tip is to balance the pistons when the pistons advance with pads and rotors in. If one piston is advancing too quickly, use a small flathead screwdriver to push the piston back in (with the wheel and pads installed) to allow the other pistons to catch up. I’ve also stopped lubing pistons with brake fluid; there is too much risk of contaminating the pads. The pistons get lubricated by the fluid in the system. Repeating the process of extending pistons, cleaning then pushing them back in several times seems to do the trick.