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Old 01-06-2005, 02:09 AM
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possible hard pedal

hi. to rfresh a few people, i have a 63 cadillac, and i just put disc brakes on the front end. i got my assemblies from a 69 caddy donor. i also replaced my master and booster with new or refurbished 69 units. i finally got the job done with much headache, and now its at the driving point. the car seems to operate fairly normal with the exception of this possible hard pedal issue. to me, it seems i have to use more force when applying these brakes than i used to or than i remember. i pulled my vacuum line and gave it the the thumb test, and it feels like theres plenty of vacuum. and if i really step on these brakes i CAN get the car to stop. it just doesnt have that stopping power that i would have expected from disc brakes. like slamming me off the dash bord and just being all around sensitive brakes. is there something i missed? or something i could look for to find out if it stops correctly? i know that it almost feels like im getting no assist from my booster. very strange. these are all new or rebuilt parts. so any helpful hints would be apprecciated. thanx so much blackbeard

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Old 01-06-2005, 04:24 AM
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here is a cure

not a "expert" on Caddy brakes so do make sure with a someone that your conversion/brakes are correct.

Here's the cure: it's a "brake peddle" leverage problem, more leverage/less travel.

Use a slightly longer rod from the peddle into the master cylinder, as long a rod as your peddle "full up position" will allow.
It dramatically increases the mechanical advantage/leverage so less foot pressure is required, a 1/4 to 1/2" is plenty

Don't have a longer rod?
I've used an aluminum bushing, piece of 3/8" rod, etc. (loose but close to the master cylinder bore diameter) in front of the stock rod, in the master bore to make the rod longer.

Reason it takes a lot of force: probably a tiny "un-balanced" size difference between the 69 master and the still (?) original rear wheel cylinder size.

It works, done it on 5 cars, works on stock brakes with no power assist also, less travel/ less force/firmer peddle

(And I love it when the improvement/cure costs less than (?) a buck!!!!!!) .

Last edited by red65mustang; 01-06-2005 at 04:55 AM.
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Old 01-06-2005, 10:22 PM
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If you are sure you have the lines and all hooked up correctly, and the booster is working, check valve and hose are good, vacuum is good, firewall side of booster is open to atmospheric pressure, no brakeline restrictions, etc...

The longer pedal would work. An alternative would be go from your 1 1/8 bore master to a 1 1/16 bore to increase line pressure. It will drop the pedal slightly, so I hesitate to do that except as a last resort. Look for something else wrong first.

Here is a list of a few things to check:
http://www.mpbrakes.com/trouble11.htm
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Old 01-07-2005, 12:25 AM
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heres a thought

i failed to mention that i added a 1/4 spacer between the firewall and booster.. i did this because when i put it back together i noticed that my pedal height was rather high, and so i figured by shimming the booster out a 1/4 or so, it would lower my pedal height to a hair higher than my gas pedal. i was mainly shooting for comfort. heres the exact setup, pedal goes through to 1/4 in. spacer (which is made out of black micarta, it has 4 bolt holes, and of course a large hole in the middle for booster arm to connect to pedal.) anyway, pedal to spacer, then to 69 rebuilt booster, and then connected to 69 rebuilt master, then the lines head to the proportioning valve, which is brass, has 2 inlets and 2 outlets, witha dummy light post on it. this proportiong valve then connects to my old brake lines. using only one brass fitting to make them work. these lines trail off to the rear where nothing was changed, and then to the front where i added some hard line to allow me to continue using the 63 size hoses. then of course onto both disc assemblies. new pads new rotors new bearings. there is also a 5/16 spacer on my rotors to help me clear the calipers so i can keep my old rims and caps. i also had to shave some meat off the calipers because they were scraping otherwise. so that brings us to now. so about the ideas given to me. ok i think i understand the adding to of the pushrod between the master and booster.. on my old booster(63') it had a removable rod that was adjustable. on this new booster,, i dont remember seeing that. now heres what i dont get, if i added to that rod btween booster and master,, i would think it would make my pedal harder to push than it already is. i was thinking if there was less than it would give me more movement before brakes grab hold causing less pressure?? so im sure your right with your theory, i have no doubts but maybe you could help me to understand even further.. as for yesgo's thoughts. i was not aware of the atmospheric pressure thing you speak of.. could you further explain that and help me to make sense of that as well.. also now that i gave you the exact run down of whats under the hood, maybe it might help to clear more things up for readers. so again the car will stop. but the response time seems sluggish. not sure of the cause but if i "two foot" it.. it will stop. just not clean, and very sketchy feeling. in fact today i might have noticed a little shaking as i come to a hard brake. same feeling you get when either a rotor is warped or brake drum. but that would be wierd cause i have both new rotors. very frustrating to be in my shoes.. sometimes i feel like i cant just a win a simple victory of this car. i would very much like for something to go right on this vehicle. anyway so far everyones input is great.. and im thankful for your time.. sincerely blackbeard..
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Old 01-07-2005, 04:51 AM
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blackbeard

Did you "bench bleed" the master cylinder before you installed it?

I would bleed all four wheels again and do it in what ever order is correct for a Caddy. Some cars are a pain in the butt for air in the lines and need to be bleed 3-5 times.

MOVE THE MASTER BACK!!! to where it was originally mounted. You changed-lost leverage because you moved-changed the fulcrum-pivot point by adding spacers. With the spacers, the rod is not straight, it may be binding.

I'll bet that helps alot, you made a "shorter" rod with the spacers.

Agree with yesgo, a smaller bore cylinder will drop the pedal height for your driving comfort. Get all working with what you have now, shop and swap later for a smaller bore if you want.

Yesgo didn't, and I didn't try to explain the leverage geometry cause you have to draw a sketch for it to make sense, longer is more pressure, shorter is less......
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Old 01-07-2005, 07:20 AM
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I went through a very similar situation when I put disc's on the front of my Ranchero...Did you install the '69's proportioning valve setup too?
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Old 01-07-2005, 07:29 AM
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the idea about having the longer rod for leverage, is that basically the same concept as using a cheater bar or breaker bar on a ratchet or wrench while trying to get a hard nut or bolt free?
so ya everything i believe makes sense now, however i didnt move the master or shim it at all. i shimmed between the firewall and booster. and the only thing that could possibly change there would be the rod that attaches to the brake pedal itself. and since the rod sits on a shaft or nub, it a free moving part that rotates. so im not sure how it would put it in to much of a bind.
so i bench bleed my master when i got it. it came with some caps so i plugged the prts and plunged the master slowly every 20 secs or so about 20 times.. or basically till the air stopped bubbling up. i have bleed the car 2 times. and i def dont have soft pedal issues like i did. im not sure i follow you on what a smaller bore cylinder is. would that require me replacing both my master and my booster? thanx again
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Old 01-07-2005, 08:11 AM
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blackbeard

(side note: forgot to say thanks for the chuckle....you wrote: "thanks blackbeard"....bet the real blackbeard never said thanks in his life!)

REMOVE THE SHIMS!!!! doesn't matter if they are on the m/c or booster.
You reduced the leverage by shimming the booster which moved the m/c forward....

Like yesgo wrote, lets talk smaller bore later, it's a last resort. Want your pedals even, adjust the gas peddle linkage.
.................................................. ...........
maybe I confused you, when I wrote a longer rod works on a car with no power brakes also? It does but ignore that please....that was for others reading the thread.

Last edited by red65mustang; 01-07-2005 at 08:22 AM.
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Old 01-09-2005, 01:30 AM
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removing shims

ok before i remove the shim that i have between my booster and firewall, i needed to know what the deal is with the the adjustment on the rod bthat goes from pedal to booster.. are all of those adjustable? if so how do you do it.. i took the rubber boot off the booster arm and i didnt see an adjustment of any kind. what is it im missing. i am going to include a couple of snips from an article i read on this conversion.. tell me if his instructions make sense. "I avoided modifying the booster itself, as it is a service part and might be needed as a core. The actuating rod fits the stud on the brake pedal perfectly, but is longer than the original 1961 by 1/4" and left the pedal way too high in the car. I solved this by spacing the booster out from the firewall 1/4". This puts the pedal at stock height; I would have liked to have spaced it out even a bit further to lower the pedal even more but the booster would then be too close to the engine's rocker arm cover. The brake light switch was still in perfect adjustment. An alternate way of resolving the pedal height might have been to relocate the pivot point of the pedal, which could be done." this quote comes from a guy named carl mcabee he wrote a piece on installing disc brakes on a 61 caddy which is virtually the same install as my 63. in the end he liked his result. so heres what im thining.. i thinkits ok to do all the stuff he mentioned. i talked with a friend who has a 69 manual(general info) and it talked about brake issues. what to look for with hard pedal was bad proportioning valve, frozen calipers, and bad booster and a few other things. so now my curiosity comes back to the proporting valve. we talked about this for a while and he saw a pic and described it to me, and it seemed to both of us that maybe what i have isnt the proportioning valve. and that i just have a safety switch light valve. it has two functions.. dummy light in dash cluster, and also if rear loses pressure or brakes it switchs flow to front and then vice versa. so thats where the safety part comes in. but other than that i dont thinki have a TRUE proportiong valve. this would cause this problem i would think. anyone think this makes sense? i might give in and have a mechanic to a full inspection on the system and just make sure everything is correct.. although i would feel far more victorious to pull off this conversion on my own. of course not discounting my internet help. ps i read a great article in the newest custom rodder. thank you
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Old 01-09-2005, 04:04 AM
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blackbeard, last try...

then I give up!!!!

the original rod length

and the original pivot point location

and THE ORIGINAL DISTANCE FROM THE PIVOT POINT TO THE M/C PLUNGER

equals the CORRECT leverage and travel for good brakes operation.....

REMOVE THE SHIMS AND TEST IT!!! Before you start trying something else and make it more difficult to correct.
You changed the distance by adding the shims on the firewall from the pivot point to the plunger, you CHANGED the leverage.
Yes, moving the pivot point forward will work but I have never seen a car where that is even close to easy to do.

If it is not better with the shims removed, bleed the brakes one more time, still not better, do take it to a brake shop.

Work on one thing at a time, get the brakes to work first!.

Then play with the pedal height =cut and reweld the pedal, different pedal from a 69'(?), bend the gas pedal up- put extra padding under the carpet.....lots of choices to make it more comfortable.

No one can help you any further till you test without the shims
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Old 01-09-2005, 06:56 AM
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Your "saftey valve/dummy light" cant cause a hard pedal unless it's blocked up. If you were able to bleed all the brakes well, it is not likely to be stopped up.

Valves reduce pressure when told to do so. They cannot ever add pressure.

In 1969, all valving was separate for GM. See previous thread for pics and description of functions.

All you have is the Dummy light/ distribution part. Unless the shuttle valve is tripped, or it is blocked with rust/etc.., it will not prevent flow. If it prevents flow, brake bleeding will be effected, and pressure will be minimal. A hard pedal could result during light and hard braking.

If you choose to change to a combination valve, use one off a later Caddilac or other GM of similar weight, wheelbase, ride height, and brakes.


The atmospheric pressure I was talking about normally only happens if you remove manual brakes and replace with power brakes. The manual brakes have a gasket on the firewall which must be removed to allow the back of the booster to have access to the air. I doubt you have that problem.
------------------------------------------------------------------------------


The pushrod between the pedal and booster should be at an approximate 90* angle to the pedal arm, and go striaght into the booster. If you have ever seen booster/masters which mount at an angle, this is to ensure the rod angle is correct. Less than 90* can cause soft pedal, more can cause hard, both most prevelant during hard stops.

Obviously bleeding air out wont help a hard pedal. If it had air, the pedal would be spongy and low.

Changing the pedal pivot point changes the pushrod angle and the pedal ratio, which changes the leverage. Pedal ratio is determined by dividing the length between pedal pivot and pushrod into the length between pedal pivot and footpad.
With that master and those calipers, yours should be about 3.5:1 (example: pivot to rod=3", pivot to footpad=10.5", 10.5/3=3.5)

If the ratio is higher, you have more leverage (like a cheater bar). Lower, and you have less leverage.

I thought what Blackbeard was talking about was changing the pdal length or pivot point, to change the pedal ratio. Changing the pushrod length sometimes can change the Angle of the pushrod too much (90* optimal). Either way, ensure rod angle is correct.



I dont know your brakelight setup. If it is a switch activated by the pedal dropping away from it, you dont have much leeway on where your pedal is. Regardless of the switch, you want the pedal where it belongs. Changing it's height can change angles.

Make sure the angle of the pushrod is 90* to the pedal arm.

You can screw around with things like the guy you quoted, change things which change the angle/ etc... but in a hard stop when you really need it, might be the first time you find out it is inadequate. Hopefully his changes kept the rod angle straight, and did the equivallent of cancelling each other out.

The shim is okay with me IF the pushrod angle is correct. IF the pushrod angle is not correct, remove the shims and shorten the rod. If removing the shims and shortening the rod is not the correct fix to improve pushrod angle, you might need an angled bracket between firewall and booster.
-----------------------------------------------------------------

Best bet:
Take the master cyl loose from the booster. Remove Eldorado booster from car and put it in file 13.
Find your old drum brake booster or a new one, and use it. A drum brake booster and a disc brake booster are both brake boosters. They assist braking thru vacuum. Volume capacity determines amount of assist.

You know this booster is correct for the car, pedal ratio, pushrod angle, etc... Use it.

Check master cyl fit.

Look where the pushrod sticks out of the booster, and into the master. There are 2 lengths. The master cyl can be a deep hole or shallow. Both are available for disc/drum. If you need help finding a deephole, contact me and I will give you a part #.

Classic GM fitting on the master are normally
Front port, front brakes: 9/16-18, 3/16" line
Rear port, rear brakes: 1/2-20, 1/4" line

The line size may not make much difference, but then again it might. Swapping front to rear ports 'usually' causes a low pedal with insufficient braking.


If you would rather remove the shims and shorten the rod, if that improves the angles, the rod can be shortened. Many have an adjustment built in. If it does, and it is still too long, unscrew the clevis and jamnut and cut the rod, rethread, replace jamnut and clevis, adjust to pedal. If it is a fixed length, cut a desired length from rod center. Thread both ends of rod to be reused, buy 2 jamnuts and one threaded sleeve. Adjust to prpoer length, tighten jamnuts and attach to pedal.

Incorrect length of either pushrod, pedal to booster, or booster to master, can cause things such as dragging brakes, low pedal, bleeding problems, or other.

Last edited by yesgo; 01-09-2005 at 07:04 AM.
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Old 01-09-2005, 08:33 AM
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great idea yesgo!

Blackbeard,
Swap to the original booster and lose the shims = original geometry and original (?) pedal height ! It's back to factory spec!

Very clear that yesgo knows his Caddy's!

I should have thought about swapping the booster but I suffer from CRS (short for "can't remember sh##!....").

Sidenote to yesgo: I included bleeding the brakes again because he never said a "high" hard peddle.
I read it as cut the peddle mount and move the pivot point forward to level the gas and brake peddle (pain in the a##). Anyway, thanks for the excellent post, all the answers are there for Blackbeard.

Last edited by red65mustang; 01-09-2005 at 08:43 AM.
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Old 01-09-2005, 12:09 PM
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Thanks!

You were right Red, he never did mention it being 'high', just hard. I guess I just assumed it was not low. Plus air can do some weird stuff sometimes that I dont really run into often because I tend to remove it

I dont really know Caddys per se. Generally the GMs tend to follow a pattern that I am familiar with. Ford and Chrysler have their own stuff, but hydraulic brake systems are all somewhat similar in design. I get that stuff confused and backwards sometimes too, and there are always exceptions I dont count on. I have CRS too, so just 'cause I write it, doesn't make it so, even in an extra long post (That was after I cut it in half)

edit
Case in point. I think I wrote thos line fittings backwards.
front 1/2-20, 3/16 line
rear 9/16-18, 1/4" line

Knowing GM, I probably just looked at two different cars

Last edited by yesgo; 01-11-2005 at 08:37 PM.
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Old 01-09-2005, 03:45 PM
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makes sense

i agree with all the info.. i am just trying to postpone the inevitable.. i really hate doing the booster cause it sux..
about using the other original booster. i would love to have used it as it would save me time and money, however its a bendix vs. the delco moraine, and its a wierd 4 bolt setup and there wasnt a master out there set up to run disc/drum. at least i couldnt find one. it would be great to use my original booster cause its smaller round and fits better on my firewall. i need to pull the old booster again and measure the rod length on both the 69 booster and 63 booster. i thought i did this before and they were the same but when i dry fit the 69 booster, it seemed awful high. so thats whenn i added the shim. the 90degree thing makes perfect sense. that straight push into the booster has a lot less binding that a big or slight angle.. ok ill see if i can get in there and eliminate the shim and remeasure both od lengths and see where im at. you know this just popped into my head. when i was trying to fit my new booster on the firewall, i had to elongate the firewall holes down and to the left,, (towards the motor) it had to go down because of the wiper motor location(which i couldnt alter) so i wonder if the pedal is under a strain from maybe binding the rod to the right? or left? so above all the rod has to be a straight shot.
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Old 01-09-2005, 06:54 PM
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to the red

so i did it. i wasnt looking forward to it cause i hate anything to do with booster removal.. but i did it. to me it feels better. it raised the pedal close to a quarter.. i can feel that cause my shoe hits the side of the pedal everytime i go to depress the brakes.. so ya so far so good. again for all those who may have been following this thread, my caddy felt like it kind of had hard pedal and wasnt wanting to stop with ease.. i took the 1/4 shim out from between the booster and firewall and it feels nicer.. i still have a bit of a loose chatter feeling in the front end,, not a clean smooth perfect stop.. but at least now i feel like it will stop. any ideas on the chatter? new rotors, and pads, feeling comes from front end.. red65 and yesgo.. thanx for your patience. the bearded foe
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