Manual Brakes

[Bigal75]

So I changed from power to manual brakes to make room for the HEMI. Bench bled the master bled the brakes and still have a spongy pedal. I've used the proper adjustable rod and firewall reinforcement plate. There are no visible leaks. By the way this is a 67 Coronet.
The brakes work great, it doesn't take a lot of effort but I find the pedal low. Is this normal? Have I missed something? Will lengthening the rod help?

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Does the cylinder rod bolt directly to the pedal?

 

[HT413]

The rod attaches to the pedal lever, but like half way up. Same place power or manual. I guess you changed the mc with the swap? I wonder if you have the right size mc. Too large a bore would create a really firm pedal with too much pedal effort and very little pedal travel. too small a bore creates the opposite: too much pedal travel, soft feel.

 

[A383Wing]

the rod should be one piece solid, not adjustable.....

 

[Bigal75]

I hooked it up to the pedal. So that's my mistake lol.

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the rod should be one piece solid, not adjustable.....

It's an adjustable rod...not stock.

 

[HT413]

I hooked it up to the pedal. So that's my mistake lol.

Huh, how'd ya hook it up to the pedal? This is basically what it should look like... the push rod bolts on up the pedal a bit. There's a hole on the rod to receive the bolt.

 

[Bigal75]

LOL well, theres a hole in the pedal lever where the linkage was. Originally there was a linkage and rod hooked to the pedal - I assume the rod hooks up to that instead. I pulled it all out when I removed the booster.



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Is this how it's supposed to look with manual brakes?

 

[67 coronet]

on my 67 conversion i hooked it strait to the pedal where the pivot bracket used to go.pedal does feel a bit soft and a bit low,but works great.i am not gonna change it.

 

[Bigal75]

Yeah the brakes work well but I noticed the bolt seemed long but would better fit the linkage and I also noticed the pedal is low but man its easier than my power brakes Lol.

 

[nm9stheham]

You have the brake linkage that (I think) was for certain power brake models in that car. Other manual brake models did not use that 'dogbone' linkage but had the MC rod connected straight to the pedal shaft. With the dogbone linkage, the pedal throw should be 1/2 of the normal pedal throw; throw should not be longer than normal. (At the same time, the leg force should be much higher; the booster would make up for this with power brakes but not for manuals.)

Do you have a 1" bore in the MC? And is this disc/drum or drum/drum?

When you say the pedal is spongy, if you rapidly pump the pedal several times in a row, does it become firmer and move up towards you? If so, you still have air in the system.

With the original description of low pedal, spongy, and the linkage as it is, I would suspect air is still in there.

If the system is properly bled, then I would indeed try to lengthen the rod some. Just be aware that if the rod is too long, then pistons wil not retract far enough to uncover the fluid inlet holes that sits above each piston in the MC reservoirs; these have to be uncovered to take in more fluid as the shoes/pads wear.

 

[Bigal75]

Its a drum/drum set up and it's a generic master for a 67 B body with manual brakes. Right now I've got the set up mounted to my pedal lever. are you saying I should use the linkage - and this will make it 'harder' to press the pedal? So I SHOULD be using the linkage.

The pedal does not get harder the more you punp it. It stays the way it is and seems to start applying the brakes when the pedal is 2/3's of the way down.

 

[Cranky]

The rod attaches to the pedal lever, but like half way up. Same place power or manual. I guess you changed the mc with the swap? I wonder if you have the right size mc. Too large a bore would create a really firm pedal with too much pedal effort and very little pedal travel. too small a bore creates the opposite: too much pedal travel, soft feel.

When I upgraded my 66 to a dual master, it had a slightly smaller bore and yes, it increased my travel slightly but the brakes were not soft by any means and it also lessened the effort.....

 

[A383Wing]

the dog-bone linkage is for power brakes, you need the single rod that goes from pedal to master cylinder to make the pedal work correctly and at the proper height

you will also need the correct firewall master cylinder plate to re-locate the master cylinder to the correct position for the single straight rod....that's why the dog-bone "Z" linkage is there for power brakes....

 

[Bigal75]

Ok so the way I set it up is fine. Maybe I still have air in the system.

 

[nm9stheham]

OK, I thought the pix you showed WITH the dogbone linkage was how you have it, but now I understand that you have the rod direct from the pedal lever to the MC with NO linkage. YES that is the way it should be for drum/drum manuals.

And as noted above, if the rod does not goes straight and level through the firewall to the MC but is at an angle, then you need to re-mount the MC lower on the firewall so that the rod is level. Being at an angle may be why your pedal is so low to the floor. And an angled rod will wear out the MC primary piston and seals very fast; it is not designed to have the rod at an angle.

If the pedal does not 'pump up' as you pump the brake pedal quickly several times in a row, then you should not have any air in the system. My '62 manual drum/drum system with the '67 Coronet MC goes down less than half way with the stock pedal rod.

Once you have the rod level into the MC, then adjust the rod length. You need to have the pedal hard with no more than 1/2 of the brake pedal travel. My '62 manual drum/drum system with the '67 Coronet MC goes down less than half way with the stock pedal rod.
If it goes down more than 1/3 to 1/2 of the way, you can lose theability to stop the car if half of the braking system fails, which defeats the purpose of having the dual MC system. The pedal will go waaay down in that situation; you will need ALL of the extra pedal travel that you can get if one half of the system fails.

 

[Bigal75]

I'll be working on it this weekend. The rod I have is at its shortest which doesn't seem right. I did use the correct plate and master. I'm pretty sure the rod is level but too short. Although the pedal is at the right height. Also the pedal is dependent on the spring in the master to return?

 

[Bigal75]

Well...went and tried to pull out the rod and the master cylinder piston came out with it. ..fluid all inside...back to square one.

 

[moparski]

did you change to a manuel master cylinder

 

[Bigal75]

did you change to a manuel master cylinder

Yes I did!

 

[A383Wing]

did you change to a manuel master cylinder

manual & power brake master cylinders are the same

 

[Bigal75]

bench bled, and then bled the whole system - lengthened the rod and all is great now.