I'm very surprised with as often as I've posted this that folks still don't know it. DO NOT EVER PUSH CALIPER PISTONS BACK INTO THE CALIPER WITHOUT DOING A FULL SYSTEM FLUSH FIRST. FAILURE TO DO THE FLUSH WILL MOST LIKELY LEAD TO STUCK OR STICKY CALIPER PISTONS AND SMOKED BRAKE PADS.
The reason is that folks do not maintain their brake system and do a flush every 2 years maximum. That leads to any sediment, oxidation debris, or just plain crap settling in the low point of the system which is the calipers. The pistons have a clearance to the piston bore about the thickness of a normal business card total or half that on each side so when you push the piston back in, you trap that crap in the bore and the piston sticks.
A normal piston seal is a square cut o-ring. When you push on the brake pedal, it moves the pads into full contact with the rotor. When you let off, the seal retracts the piston very slightly so there is no pressure on the pads and they don't drag which causes heat and eventually damage if done long enough.
The reason is that folks do not maintain their brake system and do a flush every 2 years maximum. That leads to any sediment, oxidation debris, or just plain crap settling in the low point of the system which is the calipers. The pistons have a clearance to the piston bore about the thickness of a normal business card total or half that on each side so when you push the piston back in, you trap that crap in the bore and the piston sticks.
A normal piston seal is a square cut o-ring. When you push on the brake pedal, it moves the pads into full contact with the rotor. When you let off, the seal retracts the piston very slightly so there is no pressure on the pads and they don't drag which causes heat and eventually damage if done long enough.
