08-06-2016, 10:44 PM | #1 |
Registered User
Join Date: Jul 2015
Location: Regina, Sk
Posts: 82
|
Rear Drum Brake Issue
My 67 C-10 was converted over by the PO to a 1978 5-lug front disc / rear drum setup. The issue I am having is only the top of the rear brake shoes are contacting the drum, the bottom 2" - 3" of the shoes look like they just came out of the box. I took it out to a gravel road and all the braking is being done by the front discs, I could not get the rears to lock up. The truck was fully restored 5 years ago and when I pulled the drum off for the first time there was little to no brake dust telling me the brakes have never worked properly since the restoration. All components appear to be have been replaced 5 years ago. I bled the rears and no air was present in the lines. Also turned out the self adjuster until the shoes were just starting to contact the drums and still the bottoms won't bite when braking. The drums measure 11 5/32" and the shoes are 2 3/4" wide. The booster & master cylinder are both new. The proportioning valve is rusty so it looks like it came off the 78. As shown in the picture below, the portion on the shoes that are contacting are a slightly different color than the portions that aren't. I wish I had measured the difference in thickness of the shoe from the top to the bottom but I forgot. Both sides have the same problem and are wearing almost exactly the same. Any ideas as to why the bottom of the shoes aren't biting??
__________________
1967 C10 SWB Small Window |
08-07-2016, 03:22 AM | #2 |
Registered User
Join Date: Dec 2014
Location: Northern California
Posts: 422
|
Re: Rear Drum Brake Issue
Are the self adjusters mounted on the correct sides?
|
08-07-2016, 07:48 AM | #3 |
Registered User
Join Date: Jul 2015
Location: Regina, Sk
Posts: 82
|
Re: Rear Drum Brake Issue
Not sure...What determines if they are on the correct side? The pic above is of the drivers side.
__________________
1967 C10 SWB Small Window |
08-07-2016, 08:10 AM | #4 |
Registered User
Join Date: Dec 2004
Location: Highland, IN
Posts: 2,326
|
Re: Rear Drum Brake Issue
I could be wrong. But if I recall the larger of the two shoes goes on the front. If this is the driver side it is backwards
__________________
Chris _______________________________ 1979 Chevy Stepside SPORT 2018 Chevy Silverado, 39 years apart My build 2008-2016. http://m.imgur.com/a/bURrE |
08-07-2016, 10:05 AM | #5 |
Registered User
Join Date: Dec 2014
Location: Northern California
Posts: 422
|
Re: Rear Drum Brake Issue
Easiest way to check is when you push the lever down (multiple times to actually see movement), the shoes should expand out. Other thing to check is if backing plate is grooved.
|
08-07-2016, 11:12 AM | #6 |
Registered User
Join Date: Jul 2016
Location: Sutherlin, Oregon
Posts: 162
|
Re: Rear Drum Brake Issue
Sounds like part of the proportioning valve has gone overcenter, a safety (?) device to isolate front from backs in case of a leak or other failure.. I had the same problem on a 67 I used to own, it had 71 brakes installed on it. i have no idea how to recenter that valve, there is a tool one can buy that screws in place of the brake failure light switch that prevents the valve from closing. Hope this helps. I think your rear shoes will center themselves when you get pressure to them.
Bob |
08-07-2016, 01:01 PM | #7 |
Registered User
Join Date: Feb 2016
Location: Weatherford Texas
Posts: 306
|
Re: Rear Drum Brake Issue
|
08-08-2016, 12:13 AM | #8 | ||
Registered User
Join Date: Jul 2015
Location: Regina, Sk
Posts: 82
|
Re: Rear Drum Brake Issue
Quote:
Quote:
__________________
1967 C10 SWB Small Window |
||
08-08-2016, 09:53 AM | #9 |
Registered User
Join Date: Jul 2016
Location: Sutherlin, Oregon
Posts: 162
|
Re: Rear Drum Brake Issue
There has to be a way to reset that valve, they are too spendy to replace every time one might get tripped. Try taking the switch out and using a pin punch see if the groove is in middle of the hole, you won't lose any fluid taking that switch out. Another hint when working on brakes, contrary to what some instructions and manuals say, the front part of the master cylinder works the rear brakes and the rear works the fronts.
Bob |
08-08-2016, 01:46 PM | #10 |
Registered User
Join Date: Jul 2010
Location: MD
Posts: 1,937
|
Re: Rear Drum Brake Issue
Threads. One with left-hand thread goes on passenger side. Right-hand thread on the driver side. That way when the lever pushes down on the star wheel it will unscrew it.
__________________
1969 c-10 Step Side Long Bed. I-6 250cid = = 1969 Pontiac GTO hard top. 400, 4-speed. |
Bookmarks |
|
|