Disk still rubbing.

[Yellow Saddle]

If that little anti-rattle spring is strong enough to push the pistons back to their starting position then I'm a helicopter pilot.
@keithmac it ain't no shim either. It simply prevents the pads from shaking around.

 

[Kajjal]

It keeps the pads in the right position against the piston. It is not strong enough to push the piston back.

Assuming hydraulic disc brakes the below can cause rubbing :-

Warped rotor
Misaligned wheel insertion
Wheel is not done up tight enough
Pad damage
Debris on disc, pad or behind pad
Pistons need to be reset back into caliper
Caliper is not aligned properly
Too much brake fluid leading to very small pad / disc gap
Brake pads not fitted properly
Rotor is loose

Just take your time and you will soon work it out.

 

[midlife]

Easy. In hydro disc systems the piston seals act to return the piston once the lever is returned (ie you stop braking)

Is it a spring though (does it store energy to keep the pad against the piston). ....

Shaun

 

[Andy_R]

As I've said above, it returns the pads to their resting position. The spring in the brake lever determines the caliper position. The pads are floating, so the flat sping in the brake assembly pushes the pads back into place against the calipers and keeps them away from the disc, preventing un-neccessary wear. Simples...

 

[T.M.H.N.E.T]

The spring in the brake lever determines the caliper position.

The calipers in a disc brake system are fixed to the frame/fork by 2 hefty bolts.

The pads are floating, so the flat sping in the brake assembly pushes the pads back into place against the calipers and keeps them away from the disc, preventing un-neccessary wear. Simples...

No it doesn't push the pads back against the caliper, it holds the pads away from the disc and against the piston, and also helps prevent noise.