Another brake question

[Houston Ben]

Thanks for all the replies,
Ran into a snapfu last night. I had the drums off to look at my true trac so while they were off I had my wife push on the brakes. The driver side rear piston did not move at all and the passenger side moves a little and it took approximately 1/2" a second to do it, real slow like. As the pistons are new I guess I will be replacing the rubber brake lines. Also, how do you the safety valve inside the proportioning valve??

Thanks again!