I did my back brake yesterday and i let some of the fluid out while putting the caliper back on. After that i bleeded the breaks and put more brake fluid in. But today when i went to work i noticed i had to push the brake pedal halfway in for it to start braking. Before as soon as i touched the brake pedal it would start stopping. Could it be because i didnt put those thin backing plates back in? Or did i still leave air in the lines. please help.

 

To me it sounds like you still have air in the lines. I had done the similar goof up once and it took a while to get the air out of the line. Are you taking about the black plate that goes behind the pad? If so, that wouldn't make a dramatic difference in the amount of distance the pedal goes down.

Also, make sure you don't have a "leak" in the line anywhere. Make certain it is airtight and there is pressure.