i have a quesion about the "pistons" in the calipers. do both of them push in? (outside one, pushing pad towards the car, and inside one pushing out from the car). do they both squeeze the pads into the rotors, or is only one suppose to move?

i thought btoh move. but i been told only one does. if i am right i mght have a stuck piston, and how would i fix this? thanks

ned

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198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05