New answers tagged hydraulic-disc-brake
Your brake is a closed system, and your brake cable is filled with a mixture of brake fluid and air. Air is compressible, while brake fluid isn't. So, the larger the proportion of air in the system, the more compressible it will be, the more effort is required to actually stop the bike, and this is frequently described as "spongier". Now, in your specific ...
The space is normal and overfilling should not alter this (over bleeding can be used to improve lever feel though see this blog article from Epic bleed solutions). As you say the pistons will adjust automatically. The gap left should be equivalent to the displacement of both pistons by the master cylinder (lever). That said if the calliper was not centred ...
Short answer? No, it will not generally cause you a problem. This is actually a common method of parking a loaded touring bike. Don't over tension the brake lever. Remember that a hydraulic lever doesn't require excessive force to have power at the brake. A simple 6mm rubberband wrapped over the lever and handlebar should accomplish your purpose.
The metal "R" shaped piece is likely the brake return spring (#7,8 in the image below): If it is visible as you describe, you are likely missing a brake pad, and the spring is contacting your rotor. You will need to find or replace the pad to fix the issue.
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