Rear Brake Caliper Questions Options

[ljubodraz]

Firstly, many thanks to Eric Shea and the rest of you who have written threads that are helping me rebuild my rear brake calipers on my own.

I've got a few questions so far as I wait for parts:

1. What is the purpose of the mechanism within the brake pistons? Does it allow the piston to extend and retract beyond the limits of the adjustment bolt that threads into it?

2. Is there anything I should do to test that it's working properly?



3. I see that Eric Shea recommends and uses Permatex Ceramic Extreme Brake Parts Lubricant for assembly purposes. I've also seen other threads saying to only use some hard to find $$$ ATE paste. Aside from lubricating the parking brake mechanism that pushes the internal bolt, can't I (should I) simply use brake fluid to lube the pistons and seals during assembly? Unlike Eric's calipers, mine won't be sitting around too long before being installed preventing the brake fluid from absorbing water.

[ljubodraz]

Okay. I'm following up on my thread here from a few weeks ago....

I'd like to share something I think I learned about our rear calipers that perhaps not all of us know. From what I read in the factory service manual, the rear caliper venting clearance is supposed the be self adjusting with pad wear. It appears, however, many of ours don't do this well anymore due to age and maybe stress imposed from rebuilds. Many, including our in-house expert Eric Shea, recommend checking the clearance once or twice a year. What troubled me is that I've never read anyone here clearly stating they're supposed to auto-adjust.

This starts to answer the original question I had about the mechanism in the pistons of the rear calipers. Having removed the mechanisms for cleaning, it was clear to me that one function is to allow the piston to extend a few millimeters beyond the position of the threaded adjuster bolt when brakes are applied. In my later model mechanisms, the extension is made possible by compressing two spring (wavy)washers towards the front of the pistons.

What troubled me was the purpose of the wound up spring visible at the back of the mechanism. (See picture in my original post above.) Apparently, this spring helps the mechanism unthread the piston from the adjuster bolt just a tiny bit each time the piston is forced to gradually extend further with pad wear.

My original question was whether there is anything we can do during a rebuild to ensure the mechanism is working properly. This I don't yet know. It would take a bit of force to extend the mechanism to test the winding action. I don't want to break it.

Anyhow, this helped explain contradictions I've read here regarding the matter. In particular, there was once a post by our late Cap'n Krusty indicating in all his years of experience he has never had to adjust the rear venting clearance or parking brake between pad replacements. This was going against everything Eric Shea was indicating and it bothered me. I now think maybe the Cap'n spent more time with this when our teeners weren't as old and most mechanisms still worked. Eric is perhaps more familiar with calipers that weren't maintained by dealer mechanics.

Sorry for the long post but this is interesting to me. Please let me know if I'm wrong about this stuff as I respect the knowledge available here on the World.