Originally Posted by
Mattyb13
Thanks. I loosened the bleed screw, and tried to push the pistons back with the bleed screw out. Helped a little but still have some rubbing. Im wondering if I need to do this again? Dont want to let too much fluid out of the system.
Totally the wrong thing to do.
Everyone chiming in on here that doesn't actually work with these daily is really just handing you a loaded weapon without educating you on how to safely use it.
SRAM brakes... Well...let me just say I know enough of the engineers that design them that I don't like to publicly talk a lot of smack abut them but let's just say there's lots of opportunities to practice and become a subject matter expert with them.
Because of the design the pistons WILL eventually stick. Did 4 or 5 bikes this week with that problem. I have disagreed with the engineer that designed the lipseal setup. This seals are designed to have a little friction with the piston and flex as well as slide so that there is some back force to help with retraction.
It's a great idea but in the real world it's complete trash. The seals will eventually dry out enough that they essentially weld themselves to the pistons. Usually happens further down in their life. Most road users have the problem towards the end of their first full set of pads if it's taken more than a season or so. When they stick most riders don't even realize it because they end up just losing some throw towards the end of the pad life. They assume they need new pads and swap them. Then get into this situation.
You can put some oil on the pistons (to state the obvious - make sure the pads and rotor are nowhere near that oil) then cycle the pistons in and out a bunch. Saw a hack somewhere that was something along the line of putting a 4mm hex wrench in between the pistons to help keep them from popping too far out. I just do it by eye and sometimes use a half cut bleed block.
I cover a way to do it with their DOT grease in one of my YouTube channel's videos on their systems (yes Anthony couldn't hold the camera still and I apologize). I was confronted after doing that video regarding the grease. Engineer who designed it said, "don't use the grease. It will reduce the retraction." My response was along the lines of, "the brakes just won't work without it." The engineering manager said, "I have a feeling this is one of those 'it was designed to be one way but the mechanic in the field knows how it really works. Both are valid.' situations." He's a great person and an immense asset to SRAM.
End of the day - your pistons are stuck. Push them back. The master cylinder is build to bypass the fluid. No fluid was added to your system. There is a reservoir. Anyone who said you had too much fluid is so wrong it hurts. Instead, now, you don't have enough fluid and probably introduced air into your system and now need a bleed.
If you have to take it to a shop because you don't have the tools to do the bleed please know this: The vast majority of shops have absolutely no skills or ability to work on, troubleshoot, or fix SRAM brakes. They will call it in to service after trying to bleed the system 4-5x without success and SRAM will warranty them and replace them. With the current part shortages that could leave you stranded for a long time. Get them to someone that knows what they're doing.
If you had put a tiny bit of oil on the edge of the pistons and cycled them at the start you'd be done. BTW when they are floating well then be sure to clean off the excess DOT fluid with rubbing alcohol.