moparodbuster
moparodbuster
Now that I've put '75 discs on my '72, will I need to replace my manual brake lines or add a brake booster?
Disc upgrade question...
- Thread starter moparodbuster
- Start date
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Nope
Just the hoses from the frame rail to the caliper.
Just the hoses from the frame rail to the caliper.
moparodbuster
moparodbuster
Thanx... thats good news! So the orig master cyl, and lines can stay... I wonder if the lines from the framerails to the calipers are avail. aftermarket? And where abouts in the system would the proportionong valve go?
The lines are readily available at most auto parts stores. Just make sure they understand it is for disc brakes. You already have a proportioning valve for the old drum-drum system. I'm just asking for someone to chime in to confirm whether you should swap it for a disc-drum valve. It is the device mounted to your frame rail that has the two coiled brake lines running to it from the master cylinder. It also has the single wire clipped to it that carries the signal to your "BRAKES" idiot light on the dash. When you press the brake pedal this valve "proportions" a certain amount of line pressure to the front and a different amount to the rear.
You need to use a proportioning valve for a disc brake car.
A valve like the one pictured, is used on the 67 to 76 a body disc brake cars.
A valve like the one pictured, is used on the 67 to 76 a body disc brake cars.
Southernman
Well-Known Member
If you swapped from the small drum front brakes to the disc brakes, the master cylinder is not the same. As pads erode, the disc calipers require much more fluid during actuation than the small wheel cylinders you replaced, which means when the drum MC is at low fill (pads wearing out), you run the risk of accidentally purging the MC. I suspect the only reason some of my friends get away with it is because they never let the fluid run down enough to "test that theory"...
While I have heard of guys running the drum master with the discs, I've always changed the master to ensure the larger reservoir matched the capacity of the caliper pistons throughout the life-cycle of the pads.
The best way to approach it is to look at the master cylinder from the car you pulled your brakes from. Chances are it will have the larger front reservoir, which should be matched to your set up and, as noted above, get the proportioning valve if possible, since you will be doing some re-plumbing anyway.
Just a suggestion and good luck on that hotrod !
Southernman
Robbie2734
Lambcharger
I tried to run a drum master cylinder and it doesn't work. The drums need 10lps of residual pressure and will lock the front disks up. I was told it wouldn't and found out otherwise. Get a small bore disk brake master cylinder and matching proportioning valve and you will be good to go (and stop)..
Southernman
Well-Known Member
Robbie, thanks for the reply as I just remembered; my buddy uses an adjustable proportioning valve, which will allow you to use the drum MC, however, for the safety reasons I cited above, I'd never mis-match them.
Southernman
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