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Lack Luster Brakes

70VCode

Well-Known Member
Local time
7:35 PM
Joined
May 14, 2018
Messages
58
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Location
Pennsylvania
So the car in question is a 70 charger. It has 10" drums all around that were rebuilt with new springs and cylinders a couple years about (about 1500 miles ago), with a repro disk brake booster. I bled all the air out of the lines and verified that there are no leaks in the system. However my issue is under heavy braking I can not get the wheels to lock up (from a 10-15mph roll). So the pedal does not go to the floor, but it does stop before it gets there, it is solid.

so here are a couple ideas I have that may be the reason for my subpar braking:

So the car was always a power brake car so I don't believe there is an issue with the brake pedal length, but to be sure is there a way to determine if I have the correct power brake pedal?

This is the second brake booster on this car. I adjusted the push rod length that protrudes into the master cylinder. I believe I left about a .015" gap between the tip of the push rod and the corresponding cup in the master cylinder. Is that too much or not enough? I thought it was enough from what I found online. Like stated above, the brake pedal is solid but could it be that the master cylinder doesn't have enough travel?

I did feel the wheels after the test drive and they did feel like they were really warm? could it be that the push rod is to far extended into the master cylinder to the point the brakes are dragging and they are getting hot to the power that they are losing their effectiveness?

The last idea I got was maybe the adjusters are not locking into place due to that lever not contacting the star part of the adjusters. So after a couple stops the adjusters work themselves in? I did go in reverse a couple times and slam on the brakes (which I thought was a way to help adjust the brakes out?) and it did seem to improve the braking, but it was at the end of my drive and didn't get to test anything further.

Am I on the right track? is there ways I could prove if any one of these ideas is causing the problem of lack luster braking?
 
If the pushrod is extended to far the brake pedal will be right up to the top and the drums will have drag if you try to spin them...

You shouldn't need to slam on the brakes, backing up & hitting the brakes fairly normal should cycle the adjusters... I would do more of that and reevaluate....
 
It may just be the material the shoes are made from everything else sounds pretty good.
 
It may just be the material the shoes are made from everything else sounds pretty good.
I mean maybe... but when I drive my 68 dart with 10" drums in a similar manor (10-15 mph and standing on the brakes) it will damn near throw me through the windshield! front comes down and that car stops. Similar reaction in the 70 polara. However, with this car it just slowly stops. Which driving on the high ways around downtown Pittsburgh Pa is a recipe for rear ending someone. The dart has similar parts store brake shoes

its a charger with a 440 and 3.55 in the rear. It likes to get up and move and if I can not confidently slow down when there is a curve or someone in front of me slows down that is a problem.
 
Used to be that brake shoes
were ground down to match
the curve of the drums. It
wouldn't surprise me if it
was found that the shoes
are contacting the drums
only on the high spots.
Cheaply built chinese junk
and all.
Pull the drums and make
sure the shoes are making
full contact.
 
Is it possible you got oil or grease on the shoes during your work? Even if you cleaned them off I've found any oil impregnated in the shoe really degrades performance.
 
Used to be that brake shoes
were ground down to match
the curve of the drums. It
wouldn't surprise me if it
was found that the shoes
are contacting the drums
only on the high spots.
Cheaply built chinese junk
and all.
Pull the drums and make
sure the shoes are making
full contact.

I really hope your wrong... lol. But it is easy enough to determine. Ill try that this weekend since they are calling for rain the entire time!!

Is it possible you got oil or grease on the shoes during your work? Even if you cleaned them off I've found any oil impregnated in the shoe really degrades performance.

I mean anything is possible? the axle & bearing seals were new once the brakes were installed and I am usually pretty diligent on keeping my hands and work area clean, but I guess anything is possible. Something I can look for once the drums come off, thanks!
 
So I made some time last night to look into the charger and found a couple interesting things. First off, like I vaguely remember, the adjusting lever was not contacting the star on the adjuster. I am chalking this up to mismatched parts from the original components mixed with todays revised design of moving the star closer towards the center of the adjuster.

IMG_2561.jpg


So even if I would have adjusted the front, eventually they would have just "unwound" them selves and I would be back at my initial issue. Speaking of adjusting, I believe I got the adjusters on the wrong sides. Since if you were to use a brake spoon and push up from the back side of the backing plate that would loosen the adjuster and not tighten it.

The other lovely issue I found is that I have a leak in the left front.

IMG_2562.jpg


I guess this isnt a good picture but you can see how shiny the pad is. I think at one point or another the wheel cylinder leaked. So I have new adjuster kits on order as well as new front cylinders and shoes. Hopefully they will be here Saturday so before the holiday weekend is out this will be on the road.

The inspection of the rears showed a good wear pattern and everything appeared to work the way it should. So it looks like I really only had rear brakes working on this car.

Ill get these issues addressed and see if that cures my lack luster brakes.
 
IMO, you have a bunch of mis-matched parts that are causing your issues. More often than not, people seem to think "brake parts are brake parts" which is just not so. First off.....Why did you replace your drum brake booster with a disc brake booster? Usually it is the other way around. People upgrade to front discs and try to use the drum brake booster which only provides half of the boost needed for discs. I have not had any experience with using a disc booster with drums but I know the other way around is taboo. Also you definitely have mis-matched adjusters on the front. Maybe on the back as well. Good luck finding a workable combination.
 
IMO, you have a bunch of mis-matched parts that are causing your issues. More often than not, people seem to think "brake parts are brake parts" which is just not so. First off.....Why did you replace your drum brake booster with a disc brake booster? Usually it is the other way around. People upgrade to front discs and try to use the drum brake booster which only provides half of the boost needed for discs. I have not had any experience with using a disc booster with drums but I know the other way around is taboo. Also you definitely have mis-matched adjusters on the front. Maybe on the back as well. Good luck finding a workable combination.

I had an issue with the drum brake booster a year or so ago. And instead of paying the money to get it rebuilt I went with the disc brake booster knowing that I would eventually put disc brakes on this car. The disc brakes I want to use on this car require a wheel change to a bigger diameter so I am not going to do the conversion until the tires wear out or age out. So in the mean time I would like the brakes to just work so I can drive the car.
 
I had an issue with the drum brake booster a year or so ago. And instead of paying the money to get it rebuilt I went with the disc brake booster knowing that I would eventually put disc brakes on this car. The disc brakes I want to use on this car require a wheel change to a bigger diameter so I am not going to do the conversion until the tires wear out or age out. So in the mean time I would like the brakes to just work so I can drive the car.
OK. Carry on my friend. Hopefully the extra boost won't be an issue for you. So it also sounds like you want to do a non standard upgrade to discs in the future since you said it requires a wheel change. If you were to use the correct discs, they would work with your stock wheels. In the mean time at least get the correct adjusters for your current drums. Sorry I couldn't help you any.
 
Post a picture of the booster...

Please tell me it doesn't look like this...

600-3753054762.png
 
Post a picture of the booster...

Please tell me it doesn't look like this...

View attachment 1668283
Randy, what don't you like about that booster? Weren't these gold finish style boosters stock in some of the Mopars? Does it perform bad? I'm just curious because I was running one in my car before I switched to a newer Bendix just to try it.
 
Randy, what don't you like about that booster? Weren't these gold finish style boosters stock in some of the Mopars? Does it perform bad? I'm just curious because I was running one in my car before I switched to a newer Bendix just to try it.
Those boosters were never stock on any vintage cars... First application I'm aware of was a mid 80's Mazda... The real Japanese version isn't a bad piece for lighter cars but the ones sold by CPP are Chinese...

I'm guessing the booster your thinking of is the old Midland Ross piece... Common on power drum brake B bodies through the 60's & early seventies..

I personally swapped four of the CPP units onto a customers car before I finally laid down the law & told him we are installing a reman OE booster... The OE booster fixed his brakes..

A friend with a shop that does a lot of Street rods & GM muscle told me his shop had replaced easily 40+ of those boosters and he won't touch them anymore...
 
Those boosters were never stock on any vintage cars... First application I'm aware of was a mid 80's Mazda... The real Japanese version isn't a bad piece for lighter cars but the ones sold by CPP are Chinese...

I'm guessing the booster your thinking of is the old Midland Ross piece... Common on power drum brake B bodies through the 60's & early seventies..

I personally swapped four of the CPP units onto a customers car before I finally laid down the law & told him we are installing a reman OE booster... The OE booster fixed his brakes..

A friend with a shop that does a lot of Street rods & GM muscle told me his shop had replaced easily 40+ of those boosters and he won't touch them anymore...
Thanks for that info. What were the bad brake symptoms when running that gold booster? The one I had was part of a kit from Master Power Brakes around 2011. With that booster, my brakes had a firmer pedal, but felt a little squishy. With the new black Bendix dual diaphragm, squishy is gone, but the pedal is super duper light and a bit touchy. I got the Bendix from Dr Diff. I'm thinking of sending it off to Booster Dewy for a re-build (even though it's new) to see if there's a way to get a firmer pedal feel with more progressive control. I'm already maxed out on Master Cylinder bore as I've been running a 1-1/8".
 
The Chinese version rarely offers much if any assist... And yet finds a way to make the pedal feel soft or squishy...

Rebuilding normally makes the booster work to it's max performance so I doubt it will reduce the effectiveness.. Might give them a call and ask... What about pedal ratio? Does it have the right bellcrank?
 
The Chinese version rarely offers much if any assist... And yet finds a way to make the pedal feel soft or squishy...

Rebuilding normally makes the booster work to it's max performance so I doubt it will reduce the effectiveness.. Might give them a call and ask... What about pedal ratio? Does it have the right bellcrank?
yes, correct underdash pedal linkage (stock) and pedal. Without drilling holes in something, I should be good.
Greg and Rich drove my car and claim it's the best feeling brakes they've seen in a b-body. I believe all air is bled out, but it feels like it could be better.
Don't want to highjack OP's thread too much, but until he returns with an update on his car...

I'm going to call the booster rebuild place and see what they say.
 
yes, correct underdash pedal linkage (stock) and pedal. Without drilling holes in something, I should be good.
Greg and Rich drove my car and claim it's the best feeling brakes they've seen in a b-body. I believe all air is bled out, but it feels like it could be better.
Don't want to highjack OP's thread too much, but until he returns with an update on his car...

I'm going to call the booster rebuild place and see what they say.
Call Booster Dewey & see what he says... Actually I think Dewey retired & his son Steve is the guy doing the work these days..
 
Post a picture of the booster...

Please tell me it doesn't look like this...

View attachment 1668283

It does not look like that. I currently dont have a good picture of the booster. I can grab one when I get home tonight (time permitting)

I did put on new pads, front cylinders, and front adjusters, bled the front brakes and adjusted all for corners this weekend before I took it for a ride. I did confirm that the arc of the new pads do match the drums when I laid them inside the drum.

The brakes were better on the loop around the house. But towards the end when I came to a stop sign I did smell burning brakes and smoke coming from under the car. This was after a couple "normal" stops and the brakes were getting a little mushy. Got it back up the mountain to the house and did the same thing on my street of bringing the car up to 15 mph and slamming on the brakes, backing up, slowing down and repeat. Initially it wasnt stopping any better, but after a couple tries the nose was diving down and the brakes were locking up. So it appears the adjusters are working the way they should and it may take a little more mileage to break in the front pads. Ill take it around that loop a couple more times to verify the brakes are consistent before I start to get brave and drive it on the high ways around here.
 
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