(several?) brake issues

Gents,

I need your help, please.

Chances are that I have not only one but rather several brake problems (that interfere?).
In July I failed the 2yearly car inspection for two reasons. The total break power at the rear wheels is below the mandatory minimum. And secondly the brake force of the left rear wheel is only 50% of the right rear wheel.

What do I have: 67 Special with orginal (?) rear drums and a drum/drum mastercyclinder. Front was converted to disc (but I don't know exactly what went in, will pics later for identification) and the original 67 distribution valve.
After reading on here I understand that mc and distribution valve need to be replaced to work properly with the disc brakes.

However, my most immediate concern is how do I get left and right rear brake to perform equal? Overall looks are ok, calibration done, rear brake bleeding done several times, no dents in brake lines found, brake shoes have enough meat).
Did I mess up with the correct installation?


The self-adjuster arm does not touch the adjuster wheel (as a matter of fact it never did since I bought the car). Not original parts? Or did I make a stupid mistake. I looked at it so often now that I don't know what to do anymore.

Any help is appreciated.

Patrick

 

I would make sure the pistons inside the wheel cylinders are the same size diameter (7/8" etc). There are other sizes available so one fix could be to replace the weaker side with a cylinder that has bigger diameter pistons.

 

IF the brake hose feeding the rear brakes from the frame to the rearend is old, it'll deteriorate internally and cause braking issues. Replace it, then rebleed the rear brakes.

-Josh

 

Alright, update:
exchanged wheel cylinders and all 4 brakeshoes.
And successfully passed.

I am not able to see how this exchange cured my left, right issues though?

more questions:
do brakeshoes detoriate just from being old???
I have no clue how old these ones were but I was told they appear Rockhard.....

the pedal is not far from the bottom floor before the (new) piston start to move? The front disc is already crimping hard at this point.
Why do they get pressure so late? Something to do with valve?

 

bump.

Can brakeshoes get too old?

My front brakes already bite when the rear pistons barely started moving.
What could be the reason for this?

 

You need the correct disc/drum master & the "hold-ff" valve for the front. The fronts are applying early because the pads are in constant contact with the rotors. Whereas the rears have to overcome the force of the brake springs pulling the shoes back from contact with the drums. The hold-off valve prevents this by not applying the fronts before the rears have 300pounds of pressure 1st.

 

Thanks Tom. You are confiming what I read on the web.
And a new master cylinder as well?
Slowly things start to fit together.

I discovered the steel brake line between the T-section and the right rear brake sports a big loop. I can fit my fist into it.
That can't be original? There should only be a straight steel line like on the left side, right?

 

In your pictures it looks like the LR brakes are glazed . You said the LR braking force was only 50% of the RR . I think you cured it by replacing the Brake Shoes.

As to the brake line someone must have replaced it with a ready made length of line that was too long. They made it fit by making the loop in it. Get another lenght and Flare it at the proper length . Just be sure to double flare it.

 

The self-adjuster arm does not touch the adjuster wheel (as a matter of fact it never did since I bought the car).

This is not correct, it's supposed to stay in contact with the wheel. Otherwise there's nothing keeping it from backing off. I can't tell from the pictures what's going on.

 

Yup, I found already a couple of evidences that reflect amatur repair. Oh, well that's what happens to 48 year old cars.

Time to do the brakes properly.

 

With the new brake shoes intalled the adjuster arm now controls the adjuster wheel as it should.

 

On my to-do list.

 

You need the correct disc/drum master!!!

 

hmmm... I am trying to find out what exactly I need.
I've never done a brake job before. After the most recent experience with professional(?) shops I am convinced however that I can do it just as good, or better.

This valve?
http://www.mbmbrakeboosters.com/ind...category_id=30&option=com_virtuemart&Itemid=6
MBM offer several and I do not see much difference.
What do you think about installing an adjustable one?

and that master?
http://www.mbmbrakeboosters.com/ind...category_id=10&option=com_virtuemart&Itemid=6

Did 67 Specials have 1'' or 1 1/8'' bore?
Can I find out what I have without taking it apart?

 

Patrick, I did an MBM conversion on my '69, had power drums originally. I went for the 1 1/8" bore master cylinder. Had a few issues, but none of those were related to bore size.
From memory the factory disc master cyl was the 1 1/8" bore.
I didn't need an adjustable proporting valve, I used the MBM kit one. I did install an inline check valve for the rear drums.

Regarding the bore of your existing master cylinder, can you undo the 2 securing nuts & pull it forward enough to measure the bore? I'm not familar with the '67s to know if theres enough
'slack' in the brake line to get the master forward far enough to measure the bore.
Perhaps there is a casting number on the master cylinder you could look up?

Cheers,

Chris

 

I could be wrong on this and if i am please do chime in, but after just redoing my rear drums on my 68, the chiltons repair manual was showing that the primary shoes are suppose on the front of the drum and the secondaries shoes are on the back with the parking brake lever and adjusting lever. I am wrong with this?? Or from the pictures of the original post showing the brake shoes on the wrong sides?

Frank.

 

Short shoe to the front. Long shoe to the rear.