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66 rear drum brake woes. Cant get rear brakes to bite

14K views 101 replies 24 participants last post by  cturboaddict 
#1 · (Edited)
On my 66 mustang, I did a CSRP power disc brake conversion.

I'm ready to road test my new motor and trans (331 stroker and 4r70w trans) install. But I've got a concern.

When I installed the csrp disc brake conversion, I power bleed the system (and I prebled the master cylinder) The pedal felt odd. Sometimes okay, a bit spongy but never "stiff".

When I first started the car, the pedal went to the floor, but you could pump it up. I figured I needed to bleed the system. Had a buddy come over and bled. It got better, but not great. Never stiff/solid. I thought maybe i had the bias too far when I bled it. So I backed off the proportioning valve to see if the bias was set wrong and rebled.

I have the car on Jack stands, so I wanted to give the brakes a test before setting it down. When I put the car in reverse, with the brake pedal applied the rear tires will spin. I can pump it up and try to press harder, but can't get them to stop spinning. Obviously, this isn't desirable for an auto trans so shifting from reverse to park while the wheels are spinning isnt good for the tranny.

I thought, maybe I don't have them adjusted properly, so I tried spinning the adjusters out a few. Im turning and turning and not really getting much difference in the pad bite. (Mind you, I'm a disc brake guy and have always dreaded drum brakes with an unrealistic fear)

Tried again, wheels will still spin when in gear and brakes applied. (But with the car off I could physically feel the pedal difference after adjusting the out). I tried turning the bias to rear even more knowing its not fully counter clockwise per csrp instructions. That didnt help.

So, I thought I might need to rebleed the rears, so I did that. Again, still the wheels would spin while in gear on Jack stands. I had the tires off at this point, and when I tried to use the brakes this time, the drum shot off the passenger side bouncing off the ground.

Can come one give this knucklehead some advice? What am I doing wrong here? What am i missing? I can't test drive without brake confidence. Am I just not adjusted out enough? I can slide the passenger drum on, but it takes a wiggle to get it off. Same on drivers.

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#2 ·
You might try adjusting the rears out farther. Lots of threads on the rear drum brake adjustments after front disc conversions. I know when I had this problem, adjusting out until I could barely turn the drum and adjusted back down till the drag loosened up a little seemed to fix my issue.

Once you have the drag on the drums right. Then fine tune brake bias front to rear with prop valve adjustments.

Although rear adjustment may help some with the pedal travel, a spongy pedal usually means air in the system.
 
#4 ·
Did you try taking the drums off and adjusting till the drums won’t go on? Then back off a few clicks, slide the drum on and then adjust for drag.


Mark
No, but I will right now.
 
#5 ·
To correctly adjust any 1960's-1970's Ford Drum Brake (FRONT or REAR DRUMS), You have to bring the car on a side street or a parking lot and keep putting the car in reverse and hitting the brakes while driving in reverse. Do this about 15 to 20 times or as necessary. This brings out the Automatic Self Adjusters (Star Wheels) and the Brakes will automatically adjust themselves and the brakes will start to bite and the pedal will get harder. This all happens provided that all the Brake cylinders have been correctly bled along with Bench Bleeding the master cylinder...... What...?!??!?????.... Noone ever told you???.....lol... That's how the system works.

:eek:)

Tony K.
 
#10 ·
To correctly adjust any 1960's-1970's Ford Drum Brake (FRONT or REAR DRUMS), You have to bring the car on a side street or a parking lot and keep putting the car in reverse and hitting the brakes while driving in reverse. Do this about 15 to 20 times or as necessary. This brings out the Automatic Self Adjusters (Star Wheels) and the Brakes will automatically adjust themselves and the brakes will start to bite and the pedal will get harder. This all happens provided that all the Brake cylinders have been correctly bled along with Bench Bleeding the master cylinder...... What...?!??!?????.... Noone ever told you???.....lol... That's how the system works.

:eek:)

Tony K.
Yeah, I know about the self adjusters and the reverse thing. I figured i could get them to atleast stop the wheels when on jackstands without this though.
 
#6 ·
Initially, The Drums should be able to turn with only the slightest drag.
 
#9 ·
On my 66 mustang, I did a CSRP power disc brake conversion.

I'm ready to road test my new motor and trans (331 stroker and 4r70w trans) install. But I've got a concern.

When I installed the csrp disc brake conversion, I power bleed the system (and I prebled the master cylinder) The pedal felt odd. Sometimes okay, a bit spongy but never "stiff".

When I first started the car, the pedal went to the floor, but you could pump it up. I figured I needed to bleed the system. Had a buddy come over and bled. It got better, but not great. Never stiff/solid. I thought maybe i had the bias too far when I bled it. So I backed off the proportioning valve to see if the bias was set wrong and rebled.

I have the car on Jack stands, so I wanted to give the brakes a test before setting it down. When I put the car in reverse, with the brake pedal applied the rear tires will spin. I can pump it up and try to press harder, but can't get them to stop spinning. Obviously, this isn't desirable for an auto trans so shifting from reverse to park while the wheels are spinning isnt good for the tranny.

I thought, maybe I don't have them adjusted properly, so I tried spinning the adjusters out a few. Im turning and turning and not really getting much difference in the pad bite. (Mind you, I'm a disc brake guy and have always dreaded drum brakes with an unrealistic fear)

Tried again, wheels will still spin when in gear and brakes applied. (But with the car off I could physically feel the pedal difference after adjusting the out). I tried turning the bias to rear even more knowing its not fully counter clockwise per csrp instructions. That didnt help.

So, I thought I might need to rebleed the rears, so I did that. Again, still the wheels would spin while in gear on Jack stands. I had the tires off at this point, and when I tried to use the brakes this time, the drum shot off the passenger side bouncing off the ground.

Can come one give this knucklehead some advice? What am I doing wrong here? What am i missing? I can't test drive without brake confidence. Am I just not adjusted out enough? I can slide the passenger drum on, but it takes a wiggle to get it off. Same on drivers.
I will largely avoid the temptation to say that you should stick with only working on disc brakes...... and try to assist.

As others have said, you need to focus on the rear brakes. If you wanted to remove the rear drums, would they merely slide right off?
If so, they are not properly adjusted. Adjust until slight drag all the way around as you turn. Drag should be felt evenly, all the way around.
After this, any further issues with rear braking would see you focusing on the type of friction material in those shoes and whether your
system is bled completely. (I'm specifically wondering now also if there is a residual valve present in the rear circuit..... that would be a
good thing to verify)

ex-Global West GM
1991-1995
 
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#11 ·
Lol, no id rather have 4 wheel disc but that's another topic that I'll start elsewhere.

Just rolled around everywhere and I'm not seeing any additional residual valving unless its built into the T on the axle.

I'll say this. They did stop before when I first got the car.

Would the emergency brake have anything to do with the stopping power? The 4r70w swap has created an emergency brake looseness that i havent fully figure out just yet.
 
#14 ·
"I'll say this. They did stop before when I first got the car"
If this means that the rear brakes did stop, I think the answer to the issue is to focus on what has been changed.
You've got a power booster that's been added and (I assume) a new master cylinder? As I mentioned before, I
wonder if there's a residual valve in that rear brake port?

ex-Global West GM
1991-1995
 
#17 ·
Yes, new master cylinder, proportioning valve, and booster. Came as a kit. Took it for a quick ride. It stops, not great, and definitely not stopping hard. But I don't have the proportioning valve set yet.
 
#15 ·
On my 66 mustang, I did a CSRP power disc brake conversion.
Good choice. His stuff is based on the OEM K/H brakes.
I'm ready to road test my new motor and trans (331 stroker and 4r70w trans) install. But I've got a concern.
The road test is always a little like that, no matter how much experience.
When I installed the CSRP disc brake conversion, I power bleed the system (and I prebled the master cylinder) The pedal felt odd. Sometimes okay, a bit spongy but never "stiff".
Adjustment will remove that. And perhaps more bleeding.
When I first started the car, the pedal went to the floor, but you could pump it up. I figured I needed to bleed the system. Had a buddy come over and bled. It got better, but not great. Never stiff/solid. I thought maybe i had the bias too far when I bled it. So I backed off the proportioning valve to see if the bias was set wrong and rebled.
Proportioning valve has nothing to do with that.
I have the car on Jack stands, so I wanted to give the brakes a test before setting it down. When I put the car in reverse, with the brake pedal applied the rear tires will spin. I can pump it up and try to press harder, but can't get them to stop spinning. Obviously, this isn't desirable for an auto trans so shifting from reverse to park while the wheels are spinning isnt good for the tranny.
You got that right. Always stop first.
I thought, maybe I don't have them adjusted properly, so I tried spinning the adjusters out a few. Im turning and turning and not really getting much difference in the pad bite. (Mind you, I'm a disc brake guy and have always dreaded drum brakes with an unrealistic fear)
Unrealistic is right. Approximately a spazillion cars had only drum brakes. For fun I drive a 5000 pound Army truck with manual drum brakes.
Tried again, wheels will still spin when in gear and brakes applied. (But with the car off I could physically feel the pedal difference after adjusting the out). I tried turning the bias to rear even more knowing its not fully counter clockwise per csrp instructions. That didn't help.
Stop screwing with the proportioning valve. It won't change pedal feel. More later.
So, I thought I might need to rebleed the rears, so I did that. Again, still the wheels would spin while in gear on Jack stands. I had the tires off at this point, and when I tried to use the brakes this time, the drum shot off the passenger side bouncing off the ground.
That's because you don't have the Tinnerman nuts that Ford provided on the rear for just that problem. You can replace them, though. I still have my originals. $4 for a set of 6 from AMK.
757383

Can come one give this knucklehead some advice? What am I doing wrong here? What am i missing? I can't test drive without brake confidence. Am I just not adjusted out enough? I can slide the passenger drum on, but it takes a wiggle to get it off. Same on drivers.

Drum Brake Adjustment 101
My Grandad taught me this.
Spin the wheel, tightening the adjuster until you can barely turn the wheel. Loosen one notch at a time until the wheel turns, with some drag. Repeat on the other side. Now you have preloaded the brakes, and removed all the free play in the parts. Before self adjusters were common, this had to be done at every oil change.


Proportioning Valve Adjustment 101
Find a smooth gravel road or long driveway. Drive at about 25 mph, gradually increasing pedal pressure until the front or rear brakes lock. If the rear brakes lock first, decrease rear brake pressure until the front locks first. If the fronts already lock first, increase rear brake pressure until the rears lock first, them back off until the front locks slightly before the rears. This is the ideal setting. You want the fronts to lock first for safety, but the rears should do as much as possible. Naturally, if the rears lock first, the car will swap ends every time you slam on the brakes, and you will die. Or at least, your car will die. This is true for four-wheel disc, too.
 
#18 ·
My man, thanks!!!
I definitely had no dive on this run.
 
#16 ·
Hang two gauges on the rear wheel cylinders. That'll be a smoking gun I assure you.

ex-Global West GM
1991-1995
 
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#19 ·
I dont know that I've ever seen a brake wheel cylinder pressure gauge.
 
#20 ·
I'm wondering if it would just be best to go ahead and put new wheel cylinders and pads on the rear?

I can buy new cylinders for less than the brake pressure gauge.

I've got a call into Dennis at CSRP about the residual valve possibility.
 
#21 ·
If you didn't take apart the wheel cylinders, I suppose they could be stuck. I doubt if the shoes would be a problem. I (many years ago) bought a 56 chevy, thought the brakes worked fairly ok, but when I pulled the drums, only one of the rear shoes expanded when applying the brakes. Took apart the wheel cylinders, and they were all corroded. I honed them out and put in new rubbers, and not a problem after that.
 
#22 ·
Why are there multiple wheel cylinders available? One for up to 4/66 and another for from 5/66-12/66?
My car already has 5 lugs.....
 
#27 ·
I also think your primary and secondary springs are reversed. Swap the green and yellow springs.
I had low pressures in my rear brakes and replacing the rubber brake lines to the wheel cylinders fixed it.
 
#28 ·
springs aren't going to make a difference for application. I didn't see anything that said anything was changed on the rear? From the photo the wheel cylinder looks wet. What happens when you apply the brakes without the drum on? The wheel cylinders aren't working or shoes are adjusted too far away. When you say they worked before, how long ago was that? If they worked before and you didn't change anything in the rear then my money is on wheel cylinders stuck or leaking.
 
#31 ·
About 7 months ago when it went to the paint shop. And in all honesty, I've only driven this to the paint shop and back since I owned it (1 min drive from my house) and the brakes in general were questionable. I know I made that statement before but I'm racking my brain to recall if I've ever had the car in this scenario before or not. (Wheels off ground and in gear)

Alot has evolved on this car since I got it..

So, looks like I've got a few definite issues here that sound like I need to rebuild the rear brakes entirely.
 
#29 ·
I just realized too that I'm missing an anchor pin plate as well..

So, springs are reversed.
Missing an equalizer bar spring
Missing an anchor pin plate/shoe guide..

Is the equalizer springs in those spring kits? And is the anchor pin plate available somewhere?

Mind you, I did NOT assemble these rear brakes.

757405
 
#32 ·
Alright...... But are you saying that not having them in there is okay? I don't consciously feel that it is....
 
#42 ·
Are you talking about the one attached to the pedal? The instructions for CSRP said to adjust that so that there was a half inch between the bumper and the support arm.
 
#41 ·
I used one when setting up my front to rear pressure in my early 65. They are useful in getting an approximation of the brake pressures (front/rear) after installing a manual Prop valve in conjunction with a conversion to a discs/drum system.
 
#50 ·
Right on. I've got new drums, hardware, equalizer bar springs, shoes, and wheel cylinders en route.

Well see how it goes. And I'll get everything set assuming it works as it should this week.

Thanks everyone for the help thus far.
 
#57 ·
CSRP sets the master to booster push rod in house and encourages to not mess with with it. I am having similar to this issue and recently correspond with Dennis about it.
 
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#58 ·
What has Dennis said thus far? I left him a message on Sunday, (figured he wasn't available) but plan to call again today.
So you're having the same problem with the rear brakes as well?
 
#59 ·
I’m having similar issues being not able to get a hard pedal with the ~15 year old Granada installation. I went to CSRP for new replacement parts and corresponded with Dennis about the push rod. He was very confident that it was set up correctly and that those “H” gauges were not reliable.
I have not yet solved the issue I keep getting sidetracked.
 
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#60 ·
Gotcha. Thanks!
 
#61 ·
So, a little update after talking with Dennis at CSRP today.

1. There is a residual valve built into the master cylinder, as his kits are specifically designed to use rear drums.
2. He recommended that I follow through with new wheel cylinders, and correct the springs/pads before looking any further. (He pointed the wheel cyl to possibly be the start of the problem)
3. He also stated that the booster/master cylinder pushrod are already preset from his shop, and highly suggests to leave it alone.

Hoping the new brake parts show up mid week, so I can get it put back together by Friday. Gonna get some insurance and see if I can get temp tags here this week as well, so I can legally drive this down the road.

And he said to give him a call if I have any trouble after that.
 
#63 ·
... I power bleed the system (and I prebled the master cylinder) The pedal felt odd. Sometimes okay, a bit spongy but never "stiff".
How did you power bleed the system? I've been trying to find an adapter for the master cylinder to do just that.
 
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