Hard brake pedal?

-
Shotgun

Shotgun

Well-Known Member
Joined
Nov 16, 2009
Messages
51
Reaction score
0
Location
Guelph Ontario
69 Dart, I have to push hard on the brake pedal to get this thing to stop. Everything is new: lines, hoses, drums on the back SSBC discs on the front, new master, wheel cylinders pads, shoes everything except the line lock and distribution block. The car used to have power brakes but was converted to manual before I bought it. The wheels will not lock up when pushed hard but comes to a respectable stop but it takes a lot of pressure even for manual brakes. Could it be the line lock (in line but not hooked up) or distribution block, Any Ideas?
Thanks
 
I'm scratchin' my head on this one.
 
The same thing happened to me when I replaced the front drum brakes on my 1970 Duster with Wilwood disc brakes. Turns out disc brakes require a lot more applied pressure than drum brakes. With power brakes the required pressure increase from drums to discs is not noticed but it sure is noticable with manual brakes. I suggest that you also read my very recent post in this forum about RedBore brakes by Just Suspension, it may keep you from making the same mistake that I did.
 
Might sound silly, and don't fault me for asking.....You make sure you have brake fluid and bled all the air from the lines?
 
Thanks green1, anything over 1 inch will give a hard pedal for manual brakes.

One other question does anyone know if the pedal ratio is different between power and manual brakes on a 69 dart? This car has been converted and I wonder of that is where the problem could be
 
We swapped from power to manual on 66340sedans 74 Satellite. The linkage as a different ratio.
Also are you using the factory proportioning valve or have an inline adjustable? Sometimes the you need to by pass the factory one and use the adjustable on the rears only.
Do you have the correct master?
 
This system does not have a proportioning valve only a distribution block with a warning switch. I am using the adjustable proportioning valve and Master that came with the kit from SSBC "I assume it is 1 inch", but I did not think to check the bore of the master, I checked the one that I had on it previously and it was 1 inch and the pedal was hard on it also. The only thing I can think of is that the pedal ratio is different between manual and power. I am hopeful someone can confirm this on an A body?
 
The power brake system uses a bellcrank between the pedal and the booster and the manual system uses a pushrod from the pedal to the master cylinder. They use the same pedal. A rock hard pedal is normal for a manual brake A body, at least the ones I've had, and the ones with disc brakes were worse than normal. The best fix I've found for this is a manual disc brake master cylinder, Cardone part number 10-1523, for a 1974 Charger with a 318. Of all the Mopars I've owned that one had the best brake pedal feel. That is what I have on my '66 Valiant and if I didn't know better I'd swear it had power brakes. These masters are available at most any parts store for around $35. Hope this helps.
 
Shotgun said:
I will try a new Master and let you know......
Click to expand...

Ok Guys I put in my new master CYL but I also removed the line lock and pulled it apart, the small hole you see is where all the fluid goes to the front brakes. this can't be right? I put the master in and made up a new line and left the line lock out, but I can not try the brakes until the snow melts :( I am sure this was my hard pedal problem....any thoughts?

IMG_1067.jpg
 
Shotgun said:
Ok Guys I put in my new master CYL but I also removed the line lock and pulled it apart, the small hole you see is where all the fluid goes to the front brakes. this can't be right? I put the master in and made up a new line and left the line lock out, but I can not try the brakes until the snow melts :( I am sure this was my hard pedal problem....any thoughts?
Click to expand...


Just to follow up my brakes are working great, the line lock was the problem....go figure?
 
Thanks for update. I recently went with a 15/16" bore master cylinder and it requires a lot less pedal effort then the 1 1/16" bore that was on there. The factory put 1" master cylinders on the manual disc cars in '69.
 
I've been having the same problem with my brakes since I put the line lock on a week ago. Can't seem to get the hard pedal I had before and I've bled the thing to death. Must be a line lock issue? I think I will pull mine off as well since it's better to stop, than smoke the tires.
 
Shotgun said:
... the small hole you see is where all the fluid goes to the front brakes. this can't be right?
Click to expand...

The small hole is not an issue when dealing with pressure. Remember that there is very little movement of fluid to the fronts, since discs run with virtually no clearance. Pascal's law - pressure is equal through out a closed system so the small hole offers no restriction to pressure - only to flow. Since there is no flow once pressure starts to build any restriction becomes irrelevant to the amount of force developed by the calipers.
 
64SignetConv said:
The small hole is not an issue when dealing with pressure. Remember that there is very little movement of fluid to the fronts, since discs run with virtually no clearance. Pascal's law - pressure is equal through out a closed system so the small hole offers no restriction to pressure - only to flow. Since there is no flow once pressure starts to build any restriction becomes irrelevant to the amount of force developed by the calipers.
Click to expand...

You need to also apply Bernoulli's principle
 [FONT=&quot]Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy[/FONT]
http://en.wikipedia.org/wiki/Potential_energy
 
You must log in or register to reply here.
-

Back
Top