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GM rear disc brake caliper

 
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WZ JUNK
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PostPosted: Wed, Feb 15 2017, 6:21 pm    Post subject: GM rear disc brake caliper Reply with quote

My rear disc brake conversion for my 9 inch rear uses a GM caliper that were originally on early 80's Tornado/Rivera/Eldorado. It has a lever activated mechanical emergency brake that adjust the piston in the caliper each time you set the emergency brake. There is some kind of internal ratchet device. I bought rebuilt calipers when I did the brake conversion. Today I finally got all the parts to hook up the emergency brake. This system needs the emergency brakes to work so that the automatic adjusters keep the slack out of the pads, and keep the brakes working correctly. I can not get the calipers to adjust and take up the slack. My search of the net did very little to help me, except some recommendations to only use new, not rebuilt calipers. Can anyone help me? I am so frustrated by the poor quality of parts today.

I looked at some older calipers and I noticed that if you remove the emergency brake arm, you can rotate the shaft and it moves the piston out. I was afraid to try this on mine until I found out more about how this adjustment system works. I do not have a manual that shows anything about these calipers.

John

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WZ JUNK
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kb426
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PostPosted: Wed, Feb 15 2017, 9:25 pm    Post subject: Reply with quote

Will this answer your questions?
https://youtu.be/i0fRR1kueQg

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WZ JUNK
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Location: Neosho, MO

PostPosted: Wed, Feb 15 2017, 9:59 pm    Post subject: Reply with quote

kb426 wrote:
Will this answer your questions?
https://youtu.be/i0fRR1kueQg


Thanks, I watched some videos this evening and I read a couple of tech articles. It is a real goofy system but I will try to figure it out. I may have found why mine is not ratcheting. Since there is so much space the piston maybe rotating and not adjusting. I will give it a try in the morning.

My patience is not what it once was, but my temper is still functioning. I threw a hammer the other day. I broke the handle of the hammer. So I made a new handle this last Sunday morning. I wrote on the new handle with a marker that the hammer is not for throwing. Maybe that will help.

John

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WZ JUNK
Chopped 48 Chevy Truck
Former Crew chief #974 1953 Studebaker
Past Bonneville record holder B/BGCC 249.9 MPH
http://purplesagetradingpost.com/sumner/hooley/hooley-2006-Story.html
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wayne petty
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PostPosted: Thu, Feb 16 2017, 1:38 am    Post subject: Reply with quote

i wonder who made this video a while back.. https://youtu.be/7CIBkoHNZx0

please be very careful when removing the parking brake lever.. i usually bend the Tab that holds the cable end only a few degrees to make it easier to wiggle out of position.. then either a small pair of channel lock pliers or a pair of duckbill pliers.. or even a pair of long nose pliers to push the spring forward just slightly to disengage it from the tab on the parking brake lever..then it will come off.


please USE EXTREME care that you don't let the high lead screw vanish into the back of the caliper.. you may have to only partially remove the nut and allow the hex to rotate or force it to rotate .. its either 14MM or 9/16 hex on the shaft.

all you have to do is get close... to eliminate the excessive freeplay shown in the video above.

when you get the parking brake lever adjusted properly.. the lever should not come off the hard stop more than 11MM or 7/16.. if it comes off a little farther... you cannot come close to hitting the cable casing bracket..

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WZ JUNK
Baron


Gender: Gender:Male
Joined: 15 Feb 2004
User's Age: (67)
Posts: 1849
Location: Neosho, MO

PostPosted: Thu, Feb 16 2017, 10:27 am    Post subject: Reply with quote

I have them working and adjusted.

After studying all the information I could find, I determined that the device works like a ratcheting friction jack inside the brake piston. I did not need to take it apart to make it start working. My reasoning was that for some reason, debris or rust was keeping it from working. I used my air hammer to vibrate the caliper and act as a sonic agitator being careful not to over do the hammer, but to use it only to vibrate. I hammered for awhile, and then I would stop and manipulate the parking brake arm, then I would hammer away some more. After several tries, it freed the mechanism, and it adjusted the slack.

"When all else fails, beat on it with a hammer", John.

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WZ JUNK
Chopped 48 Chevy Truck
Former Crew chief #974 1953 Studebaker
Past Bonneville record holder B/BGCC 249.9 MPH
http://purplesagetradingpost.com/sumner/hooley/hooley-2006-Story.html
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