I have a bike with a hydraulic disk brake and have been observing some degraded performance recently.
Yesterday I finally had a close look and noticed that one brake pad permanently touches the rotor. I tried fixing this by loosening the caliper and re-tightening the screws with the brake lever pulled, but this did not solve the problem.
So I completely removed the caliper and noticed that one piston is almost completely depressed, while the other is protruding a lot. I used a flat tool to push back the protruded piston and reassembled the whole system, but now my braking power is almost completely gone. No matter how often I pump the lever, the brake will barely stop a free spinning wheel.
What has happened? Did I suddenly get air into my system by pressing back the piston? Do I need to bleed the system to get back my braking power, or is there a simpler way? I do not feel like buying the equipment required for bleeding the system at this time.
If it matters, my bike has a Shimano BL-MT200 brake lever and a BR-MT200 caliper.