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So, I upgraded to the 12" PBR rear disc setup, and it's great overall, but I'm having a problem with one of the calipers. I finally understand (mostly) how the parking brake actually works. The "collar" that the parking brake lever (on the caliper, not the lever in the car) sort of "binds" on the piston, pushing it into the pad. My passenger side seems to work perfectly in this manner (after adjusting the set screw on the opposite side.
However, the driver's side just... doesn't work. Like, no matter how far in our out the set screw is, you can move the lever (by hand) all the way out, and it doesn't even remotely engage the pad. In fact, it doesn't seem to "catch" the piston at all. It just moves freely in and out with no effect whatsoever.
I also noticed that the set screw was missing when I first looked! I'm using a substitute to test, until I can get a replacement. (same threads).
Could something be damaged? Causing the "collar" to not snag the piston at all?
Kind of at loose ends here. It's driving me crazy.
Also, slightly related, where can I get a replacement parking brake cable? (The one from the handle to under the car, a NON self-adjusting one, my car is an 87)
I took a video today, showing what I'm talking about. The adjustment screw (the funky one I'm testing with) is all the way backed out, meaning it's adjusted for the least possible free play, but the brake isn't grabbing at all. I can move the lever almost all the way back and the collar just slides, no grab on the piston. I can try to examine the internals of the caliper, but I'm not even sure what to look for, for this problem.
I’ll take a stab at this one. I have pretty similar issues to what you are seeing. Mine work somewhat, but should definitely be grabbing harder than they do. There are two disc brake parking brake setups from the trans tunnel linkage to the e brake lever: an early model for the junk iron J65 brakes and the later setup for the PBR brakes. The PBR e brake lever mechanism is different than the early model style. What I’ve noticed on my 85 (previously J65) is that the adjuster bar in the tunnel doesn’t have a way of equalizing tension in the cables. The other issue I have found is that the adjustment procedure for the free travel adjuster (set screw on the caliper) doesn’t seem to work properly for converted setups. It’s almost like there needs to be some preload on the cables for the adjustment to work right. Might try pulling it a click or two and then seeing what that gap between the lever and caliper body is. Try adjusting with the lever in a semi-pulled position. I’m totally spitballing here, but I would love to find a solution to this problem.
To elaborate up on this, the PBR lever/linkage setup in the tunnel is supposed to be self adjusting vs the J65 threaded adjuster. The Junk65 brakes had a ratchet adjustment on the caliper itself, so there was no need to have an adjustment mechanism on the lever/linkage. No such adjustment exists on the PBRs so that’s all done at the lever/linkage in the tunnel.
FWIW, the service manual states that the brake pedal must be applied "lightly" prior to adjusting the screws in the caliper. I guess that's to take up any pad to rotor gap. I finally got mine adjusted and working really well. Turns out I was going the wrong direction with the screw. Sometimes trial and error seem to be the only thing that works for me.
I've followed those step, for the most part. Everything is brand new, so nothing is gunked up or anything. Also, the pads and rotors are brand new, so no warping/tapering.
The problem is that even with the screw all the way out (least free travel, according to manual) it still doesn't "grab" the piston, as you can see in the video. I can move the lever by hand, almost the entire range of motion, and it does just slides the "collar" without moving the piston at all.
I also did all this with the brake pedal pressed down various amounts, no change.
Also, adjusting cables isn't helpful, since you can move the lever (on the caliper) the entire range of motion with no effect, it doesn't matter what the cables do. I'm doing all my testing 100% on the caliper.
I'm wondering if the piston and/or the "parking brake collar" are worn or bad parts? If that turns out to be the case, anyone know where I could get new parts? (as opposed to an entire caliper, since it's brand new)
I'm wondering if the piston and/or the "parking brake collar" are worn or bad parts? If that turns out to be the case, anyone know where I could get new parts? (as opposed to an entire caliper, since it's brand new)
I purchased a kit once upon a time. I'm uncertain what I used from it at this late date.
So, I think the thing that isn't working is the collar shown as item #8 on this image I attached. It looks like it's not binding as it should with item #12 (or 12b, depending on how you read it).
From looking at it, it looks like the idea is that as you push on one side of #8, it binds on the piston (#12), and any further movement moves the piston, giving you braking pressure. Which makes sense, since the adjustment procedure has you move the adjuster (#23) OUT to get LESS free play. As you move the adjuster screw back, it basically pre-angles the collar, making it engage/bind faster.
It just... isn't working on mine. I can't seem to give it enough of a pre-angle for it to bind. It just slides smoothly up the piston shaft :/
I know I'm repeating myself somewhat, I'm just trying to make sure my understanding of how it's supposed to work is correct...
Unfortunately no. I've been working on other things so I've had to pause on this for now. The next thing I'm going to try is rotating the piston 180 degrees. I'm thinking maybe the piston shaft is worn, so maybe that will make it so different areas are in contact?
I feel like I'm going to end up having to pull the caliper apart and look though. Something is clearly wrong :/
With mine it appears the lever (#18) does not give enough travel to part# 6. I put about a .040 shim between the two and it works like it should--Locked.
There is no apparent wear on either part, so I'm not sure what is going on. The shim idea is temporary as I know it will not stay in place.
I'm trying to get a new lever(#18) to compare and try. Maybe it is worn?
Thanks for your update, I will follow up here on my progress if I have any breakthroughs.
Update: I was able to source a new lever (#18), didn't make a difference. Next, I removed the caliper to the bench.
I left the flexible brake line attached and plugged it with the appropriate fitting.
I removed the caliper bracket and the pads(new). I then removed the "collar assembly"(#'s 4,6,7,8,9,10) and the "clamp rod assembly"(#'s 11,12) as one unit.
The piston in the caliper remained undisturbed. I disassembled the aforementioned assemblies for inspection with particular attention paid to parts #11"compliance bushing" and #7"preload spring".
Nothing unusual was found with the exception of how part #7 was seated against part#10. Even that seemed a minor misalignment.
So I cleaned and reassembled everything.
Using a caliper piston compressing tool to take up any compliance in the piston(and take the place of the pad and rotor) and with the "lever return spring" #31 removed, I adjusted the freeplay set screw.
Next the caliper bracket and pads(new) were reinstalled and the caliper hung back in the car(new rotor also).
After bleeding the brakes and readjusting the parking brake cable everything worked perfectly. Both wheels lock hard with the handbrake lever(in the car) at about 45 degrees.
What did I fix or change to achieve this other than just taking apart and putting back together?
Not sure. I am happy that it works now, I hope it keeps working.
I'm having the same issue with my parking brake on my stock 1991 5.7L Z28: Parking brake was working with old calipers so I haven't changed the adjustment on the--actual--cable at all, but after changing the calipers, now the parking brake doesn't lock at either side at all. The levers on both sides travel to the max with the parking brake is pulled all the way up, but the push rods are barely touched by the levers in either side, let alone pushing them in properly to push the pads against the rotors. (The holes in which push rods are passing through are rather very large and allow much transaxial free movement). Adjuster screws does not adjust them no matter what. Pulled out and reinstalled after inspection to no avail. Caliper manufacturers are different (one is Nugeon 9917265 and the other is something else; one came with the bracket and the other is swapped form the old one) so it shouldn't be a manufacturing issue since both being wrong about the parking brake mechanism is next to nothing. New Wagner pads. Never had this problem during the 30 years I changed calipers which is twice. I am planning to have two longer and thicker push rods built in a machine shop , but other than that, any ideas please?
Using a caliper piston compressing tool to take up any compliance in the piston(and take the place of the pad and rotor) and with the "lever return spring" #31 removed, I adjusted the freeplay set screw.
I am convinced this made all the difference and doing it on the bench(caliper removed) allowed me to better understand what the set screw adjustment is actually doing.
Also having the caliper on the bench enabled me to make an accurate adjustment per the Helm manual.
09-05-2021, 09:42 PM
, but other than that, any ideas please? 