Converting to rear disc brakes questions.

[dart_68]

I have a 73 Duster with manual front disc and rear drums. I am contemplating converting the rear drum brakes to disc and I have some questions.

1) Do I also have to convert to power to be able to apply enough braking force?
2) Can I use the same master cylinder?
3) Do I need to install a proportioning valve for the rear discs?

Thanks for the input!

 

[Dana67Dart]

1) Do I also have to convert to power to be able to apply enough braking force

No, most of the braking force is the front brakes. I put 4 wheel disc on a F100 pickup. I had to adjust to something like 10 to 1 (IIRC) to keep the rears from locking up too fast. (500 psi in = 50 psi out)

2) Can I use the same master cylinder

Yes, but you will need to remove the residual pressure valve from under the tube seat in the MC.

3) Do I need to install a proportioning valve for the rear discs?

You should have one now but it will be tuned for drums, you might need to replace it with an adjustable one and through trial and error find the adjustment that keeps the rears from locking up too easily.

 

[pishta]

you could find a prop valve from a disk/disk vehicle without ABS to get you in the ballpark (grab MC too) but an adjustable prop valve will be able to dial it in. no front biasing will lock the rears first every time.

 

[dano]

1) Do I also have to convert to power to be able to apply enough braking force?
No, this is subjective as you might like power assist but not needed for rear discs.

2) Can I use the same master cylinder?
Yes. It is suggested to use a 15/16 master cylinder for better pedal feel, but that is not limited to just rear disc brakes.

3) Do I need to install a proportioning valve for the rear discs?
No. Dr Diff said remove it and use a Drum/Drum distribution block.

I'm in the process now of installing Dr Diff 11-5/8" rear discs (I have 13" front) and with what ever kit you buy be sure you can get parking brake lines and be prepared to make your own rear hydraulic lines. You will need to install longer wheel studs.

I do suggest avoiding the cheap kits that use a GM caliper (i.e. Summit, Jegs, Right Stuff, etc). Stick to Wilwood, Dr Diff, or Baer. There are DIY JY swaps from the Cherokee and I think some other Jeeps. I take it you have a 8-1/4" rear?

 

[dart_68]

1) Do I also have to convert to power to be able to apply enough braking force?
No, this is subjective as you might like power assist but not needed for rear discs.

2) Can I use the same master cylinder?
Yes. It is suggested to use a 15/16 master cylinder for better pedal feel, but that is not limited to just rear disc brakes.

3) Do I need to install a proportioning valve for the rear discs?
No. Dr Diff said remove it and use a Drum/Drum distribution block.

I'm in the process now of installing Dr Diff 11-5/8" rear discs (I have 13" front) and with what ever kit you buy be sure you can get parking brake lines and be prepared to make your own rear hydraulic lines. You will need to install longer wheel studs.

I do suggest avoiding the cheap kits that use a GM caliper (i.e. Summit, Jegs, Right Stuff, etc). Stick to Wilwood, Dr Diff, or Baer. There are DIY JY swaps from the Cherokee and I think some other Jeeps. I take it you have a 8-1/4" rear?

Yes but I'm swapping in a Strange S60 bought through DoctorDiff. I'll be selling the 8.25.