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]

Jeff, again I sincerely thank you for taking the time to respond. Having finished rebuilding the calipers I think I understand pretty well how they work now. It's possible I'm backwards on my understanding of kick back but I'm not convinced of it just yet.

I'm starting to understand things relating to rotor deflection and slop in joints but it seems as though you are saying the system relies on warped rotors and slop to push the pistons back. Although that may very well happen in real life, I doubt it is the design intent. I believe the basic design intent for knock back is through the wavy washers of the piston mechanism I've seen and described (late models). The other incidental knock back is the piston seals returning from deformation, as you described.

Anyhow, I'm fine with the issue of knock back. The issue of whether the rear calipers were designed to auto adjust venting clearance is what I was looking for feedback on. It appears you agree that auto adjustment was the design/engineering intent of the rear calipers.

Going back to the issue of rotor deflection, I question or disagree with something else I've read from others about it. Relating to the parking brake, many say that the parking brake extends the piston on the internal side pushing the rotor against the outer pad locking it tight (kind of like the diagram in your previous post). In theory, it makes sense until I started thinking about how brake pressure is reduced when the internal piston is mechanically extended for the parking brake. In theory then, the opposite piston can retract the same amount the other piston is extended. Because of this I don't think the rotor is really clamped down from both sides. I'm getting carried away from my intended topic and I apologize but I get excited when I think I'm learning new things.

Thanks again for you thorough responses Jeff.