55.2-59 c4 rear end handbrake setup

[QBRacing]

Just wondering what those of you who run a c4 corvette rear ends are doing for your parking/emergency brake setup.

I used the stock c4 rear cable to a camaro/nova crossover cable, a c joiner to connect to the front pully to the factory under dash brake handle. VIDEO HERE

I have adjusted the **** out of it every way I can think but i suspect its not getting enough leverage or clamping force to make the pads hold the inside drum on the rotors so i still roll downhills unless im in park.

Its the last thing i need to sort before I get my car legal on the road over here in New Zealand.

cheers in advance.

Q

[leegreen]

looking at the video, there might be a lot of friction on those i-bolts you used as guides. The cable changes direction quite a bit there. the cable will bite the bolt as it gets tight and the friction may increase dramatically. Test that theory with a dab of grease?

Trailing arm c10s had a similar guide to change angle of the cable, but the guide was free to pivot at the frame and so moves with the cable a bit. loosening your bolts might help isolate the issue as well.

If this does seem to be the problem look for 'parking brake pulley' online, they make little pulleys in a steel strap sheave that might work for you.

grease up that factory pulley you used for the same reason, if it is dry the friction will jump fast under load

Disclaimer: I have not put a c4 rear in anything but I did earn a living doing brakes for a while

[Patina56]

The factory park brake used mechanical leverage via the flat bar that connected the front cable to the rear shoes which gave it about 2 to 1 ratio. Short of fabricating something similar into your set up you’re just fighting to get enough tension on the calipers

[57FleetsideC4]

I can't really help at this point but appreciate the video to help figure that part of my build when it comes time on my C4 truck. It's funny how you have to spend all that time on a parking brake and for me I will never use it. Steve

[leegreen]

In case you missed it this summer, google for the mercury comet crash video.
There is a lot of other stuff wrong leading to the crash, but in the last seconds leading up to impact there is a memorable moment of how an 'emergency brake' is a whole lot better than a parking pawl at stopping a moving car.

It is worth the effort to build a system that works. And using it every day is the best way to keep it working.

[QBRacing]

thanks for the replies. I have someone coming to look at it this morning before work. Here is what I think is happening.

Initially the internal star pin you rotate to extend the top of the shoes out was almost all the way in so when pulling the cable only the lower part of the shoes would have been grabbing = good leverage in the cab but no friction to stop or hold truck on a slope.

I removed the rotors and scuffed up the pads and the hub face as both were brand new.

I adjusted the star pin so that the disc wouldnt go over the pads, backed it off a couple of turns so i could slide the disc over the pads, then adjusted the join between the front cable and the nova cross over to take the slack.

What I think is happening now is that I have gone to far to the other way so that only the top of the pad is grabbing. = no leverage in the cab and no friction to stop or hold the truck on a slope.

I think I need to slacken the star pin off some more so that all of the pad face grabs the disc when applied.



anyone have pics of the factory setup i can reference. I know it ran a rod to a pivot on the chassis rail, then a cable through the pully to the middle of the truck but most if not all of everything from there out was missing or modified when I got my rig.

Cheers
Q

[leegreen]

These brake shoes would mainly wear at the top of the shoe where the lever is. If used shoes are flipped them over you may have bad mismatch of arc between shoe and drum giving a small contact area, something to check.


55 to 65(ish) were some variation of this where the two cables came to a center point where a simple leaver gave 2-1 advantage as patina56 mentioned



then from 66(ish) to 73(ish) they did away with that center pivot and used a setup of cables more like yours. it still gives a mechanical advantage as front cable pulls on the center of a run of cable. I'm not smart enough to tell you if it is 2:1 still but if my memory is correct the handbrake lever was the same on the models before and after the change so there was no additional leverage there. The reason for the change was the newer transmissions sat lower without room for the pivot under them.
The rear drum components were virtually the same all years, so the tension needed at the wheel was about the same for all years.

[fauXGT]

I've set up a bracket under the dash to use and operate like the later late 50's into 60's handle. Made a fire wall mount point and welded it in and ordered 2 park brake cable kits. One pair to intercept the rear pads and a 2nd for one to go from the handle inside the cab to the tee grabbing the rear pair. They will be run thru the stock frame arm keepers on either side and under the cab to connect together. Mine is a 51 stock frame with C4 suspension.
I have no idea what the finish function is going to be, but thought of the newer cable systems for the newer brakes utilizing an old stock under the dash handle.

[leegreen]

for my AD I ended up with a '90s GM pickup pedal ebrake on the kick panel. Had to cut and rotate the pedal to get enough travel and not have it stick into door opening when released and to get a better angle on the cable.
Factory AD brake release rod was shortened and re-used.
First picture is mocked up on kick panel before it was welded in
Second picture is installed with ebrake on, pedal is down about 1/3 travel. I'll make a cover for it someday.

[QBRacing]

So I pulled the rotors off to inspect what was going on inside and too see how the shoes were wearing to give me a clue as to how to proceed...

Found one of the brackets that bolt to the lower section of the drum system to help guide to lower brake shoe was broken, and the tab had likely destroyed part of the pad at the same time.

Looking at how much the lever in the cab moves vs the lever on the drum moves to engauge I think I have plenty of travel with the eyelets but I think one of my drums just wasn't working as designed.

No damage to drum lining

New shoes
Will report back once re installed