Brakes Dragging - Pushrod too long?

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72Duster440

72Duster440

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I'll start by saying everything in the brakes is less than 2 years old.

I just swapped to a manual trans, and now that everything is back together I notice my brakes are dragging to the point where it's very hard to push the car on flat surface. If I lift up the brake pedal just a bit, they fully release. It looks like the push rod comes out of the master maybe a 1/16" when I pull up on the pedal. I switched from the stock rod, to an adjustable one from Dr Diff to get a little higher brake pedal, I'm wondering if the rod is set too long and its causing an issue?

My setup is a 72 Duster with stock 4 speed pedals, Dr diff adjustable push rod, Dr diff aluminum master, front brakes go through a line lock and to a Tee fitting, then branch off the front calipers, which are SSBC. The rear line goes right to the rear which are Dr Diffs rear disk brake kit. The flex hoses are all braided stainless lines.


I do have a parking brake hooked up, but I unhooked it and nothing changed. It just takes an ever so slight lift on the brake pedal to release all of the pressure and allow it to roll freely.


The pedal is rock solid, I can't imagine there is any air in the lines, and the flex hoses have maybe 350 miles on them.
 
I'd say you have found it. You need to figure out a way to check the rod length. On some cars, you can simply get under there (I'm 74 now, and I just pull one seat and lay on some carpet) lift the pedal and usually you can feel the play/ noise the pedal / rod makes at the top "loose"
 
So even though I have room to bring the pedal up higher by hand, the rod could be too long? I guess I thought if there was still room for the pedal to move, it wasn't too long. I guess I was wrong, again!

I'll loosen the jam nut on it and try to shorten it a tad.


Thanks
 
The master cyl internal springs are all that pushes the piston and pedal back to home location.

Maybe....

If the pedal sits too high the weight of the pedal might be keeping the master from fully returning to home.

The fact that you can manually move the pedal a bit and the master releases all pressure shows that there is something that is keeping it from fully returning.

I would look for interference, maybe the bellows, maybe the shape of the adjustable rod?
 
How straight is the angle of the pushrod when brakes are depressed.
If there is much angle the pushrod can stick on the edge of the master
cylinder. Mainly if aluminum master cylinder as that has a raised hub
and especially if bolted into firewall without adapter.

When I have had that issue - a little grinding on Master or LENGTHING the
pushrod help the geometry. Shortening it makes it worse!
 
My brake experience:
- if power brakes, the large spring inside the booster returns the pedal
- manual brakes require a separate spring on the pedal assy because there is no large spring....
 
I guess I didn't put that in there, they are manual. But there is no provision to hookup a spring.
 
Bewy said:
My brake experience:
- if power brakes, the large spring inside the booster returns the pedal
- manual brakes require a separate spring on the pedal assy because there is no large spring....
Click to expand...
Not in the USA we pull up with our toes. LOL
 
Follow up -

So it wasn't the pushrod length, I actually made it a little longer once I figured out the problem.

The bolt that goes through the pedal arm and the push rod was causing some binding. When I had it tight enough to not have any slop between the pedal arm and the pushrod, it was too tight and did not allow the pedal to come back up all the way. If I loosened it any, there was a noticeable amount of slop between the pedal and push rod. I grabbed a teflon washer and put it between the joint, tightened the nut back down and all is well again, there is no slop, and the pedal returns all the way. It's not a shoulder bolt like the stock one, it's the bolt that came with the Dr Diff adjustable pushrod.
 
72Duster440 said:
Follow up -

So it wasn't the pushrod length, I actually made it a little longer once I figured out the problem.

The bolt that goes through the pedal arm and the push rod was causing some binding. When I had it tight enough to not have any slop between the pedal arm and the pushrod, it was too tight and did not allow the pedal to come back up all the way. If I loosened it any, there was a noticeable amount of slop between the pedal and push rod. I grabbed a teflon washer and put it between the joint, tightened the nut back down and all is well again, there is no slop, and the pedal returns all the way. It's not a shoulder bolt like the stock one, it's the bolt that came with the Dr Diff adjustable pushrod.
Click to expand...
Thanks for the update, that’s good to know. I’m glad you didn’t have to buy a new pushrod.

I used the rightstuff brand brake pushrod and it didn’t come with a bolt, so I reused the stock bolt after a little sanding/polishing on the ID of the pushrod.

It’s the little things that can save future users a lot of aggravation IMO
 
MidnightSwinger said:
Thanks for the update, that’s good to know. I’m glad you didn’t have to buy a new pushrod.

I used the rightstuff brand brake pushrod and it didn’t come with a bolt, so I reused the stock bolt after a little sanding/polishing on the ID of the pushrod.

It’s the little things that can save future users a lot of aggravation IMO
Click to expand...


I just remembered I didn't post the solution, I always try to in order to help the 'next guy'. I tried to use my stock bolt, but the hole in my new brake pedal is smaller for some reason and it wasn't even close to fitting. I can't get a drill in there to drill it out in the car, and there is no way I was taking out the pedal assembly again, so a teflon washer worked great!
 
72Duster440 said:
I just remembered I didn't post the solution, I always try to in order to help the 'next guy'. I tried to use my stock bolt, but the hole in my new brake pedal is smaller for some reason and it wasn't even close to fitting. I can't get a drill in there to drill it out in the car, and there is no way I was taking out the pedal assembly again, so a teflon washer worked great!
Click to expand...
Same, whatever the outcome I try to update my threads to help anyone out. I don’t know how many times I’ve been doing a search,and read through an entire thread, to find the answer I needed was on an update that someone posted many years after the original post!
 
The worst is when it's years old and there is no response stating what the fix was when you know they figured it out at some point.
 
Or read through an entire thread, a couple pages of two nitwits arguing that their way is the right way, and the other one doesn’t know what they’re talking about, only to find at the end that there never was a solution, and now you have to do another search
 
RogerRamRod said:
Or read through an entire thread, a couple pages of two nitwits arguing that their way is the right way, and the other one doesn’t know what they’re talking about, only to find at the end that there never was a solution, and now you have to do another search
Click to expand...
Hours wasted
 
RogerRamRod said:
Or read through an entire thread, a couple pages of two nitwits arguing that their way is the right way, and the other one doesn’t know what they’re talking about, only to find at the end that there never was a solution, and now you have to do another search
Click to expand...

Wasted many hours doing that. But I've probably been one of those nitwits before too. Lol


Or the ones that link to a semi-relevant thread which has a link to another that has a link to another that kind of answers it. Just link to the final thread not the others that refer to it.
 
I have the correct original bolts and nuts with the pushrods. The bolt is a shoulder bolt for a reason and has a rubber o-ring in the center to prevent rattle. As the nut should be a top lock not a nyloc nut .
 
Oldmanmopar said:
I have the correct original bolts and nuts with the pushrods. The bolt is a shoulder bolt for a reason and has a rubber o-ring in the center to prevent rattle. As the nut should be a top lock not a nyloc nut .
Click to expand...


I have that same setup as well, but the shoulder bolt was too large of a diameter to fit in the new brake pedal I put in. Is there a different size for an auto vs manual trans setup?
 
The same shoulder bolt was used for many years on many different (if not all model) cars.
 
72Duster440 said:
I have that same setup as well, but the shoulder bolt was too large of a diameter to fit in the new brake pedal I put in. Is there a different size for an auto vs manual trans setup?
Click to expand...
Same shoulder bolt. The shoulder fits through the pushrod not the pedal . The nut goes on the pedal side after the shoulder butts up against the pedal. Your shoulder doesn't fit through hiem the That is why they give you the bolt. I see and use them on race cars . On a street car I use a factory push rod. Same push rod and bolt for Auto trans and manual trans.

I have several if needed.

I use the A body length for the Iron style 4 bolt.

Or use an E-B- body length for the newer 2 bolt with the adapter. on an a-body.

There are three different length rods for different model cars. Older cars had a castle nut with a cotter pin. There is one in the picture up on the right.

100_0022.JPG
 
Good to know, the E-B body ones are longer. I'll see how my setup works, but if I have any issues, I'd be interested in one of those longer ones, since I have a 2 bolt master with the adapter/spacer to mount it.
 
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