caliper rebuild question

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i cleaned and put new seals in my caliper. pistons were a real bear to get by the seals and were really tight. i put the assembly back on the bike w/ the pads installed and applied air pressure. the pistons pushed the pads into contact w/ the disc and when i released pressure the pads receded about a 64 th. is this normal? the haynes manual says they should move. well they move but they're really tight. thanx, rick
 

L.A.B.

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Under normal running conditions, the pistons do not pass through the seals each time the brake is applied.

The piston seals are distorted by movement of the pistons, so the part of the seal in contact with the piston moves with it each time. When the brake is released, because the seals are distorted they pull the pistons back slightly as they return to their normal shape, which stops the pads from dragging on the disc. So some piston retraction is to be expected.
The pistons only pass through the seals as the brake pad material wears down.
 
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