What happened to my rear caliper?, Handbreak stuck on Options

[larss]

Stock 914/4 rear brakes.
Pulled the handbrake heavely when parking in a steep hill, released and got away normally (I thought).
After 5minutes of driving I felt a smell of smoke and at the traffic lights felt that the car was not rolling freely.
Got home after a few minutes ...smoke from rear right...rim hot.

Took wheel off, released cable at the caliper, still sticking.
Measured the pad to piston gaps, outer 0,20mm inner one zero.
Pulled the lever at the caliper backwords (releasing), still sticking, still no inner gap.
Pistons moves freely.
Tried to adjust the inner gap but could not get it bigger than 0,10mm how much I turned it out...got less if I turned it in so adjuster seems to work ...wheel now moves freely with 0,10mm gap even after using the foot brake hard and then pulling the handbrake and releasing.

Yes, guess its time for a caliper rebuild but just cuirios what caused the problem of suddenly no inner pad gap and if its a known phenomen?
Edit: More soecific, why did the pad gap go to zero and why could I not adjust it to more than 0.10mm?

Lars S

[technicalninja]

Age is what happened.

Maybe a bit of rust in the inner piston adjuster assembly.

Even without the complexity of the parking brake adjuster the square cut seals get HARD with age and no longer auto retract the piston when pressure is released.

A new caliper (even butt simple ones like the fronts) will visibly retract the piston with pedal release. This doesn't move back much but you can SEE it when new.

At the 5 year point you cannot see it anymore.

At the 20 year point it's not doing SHIT and you magically start burning up pads.

How old is the rubber stuff in your calipers?

The fronts are gravy to rebuild.

The rears are a PIA. I'm a master and it's not really worth it to jack with the rears.

Unless you're a freaking master OR a masochist just send the rears to PMB.

If you send to PMB they also do a better job of replating/restoring than any other rebuilder I've seen. (40+ years' experience doing this crap for my dinner)

Before shipping to PMB I would set the parking brake HARD, release it, disco the cables and see if problem still existed.

If so it's time for a box...