Disc brake pedal ratio different from Drum brakes?

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71Demon

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Is the pedal ratio different on a drum vs disc brake? If so which set of pedals would I need to find to convert form drum to disc to increase pedal ratio and lessen leg effort? Thanks
 
Pedal ratio is only different between power and manual brakes. I've never had to change pedal ratio when converting to disc brakes
 
Is it manual or power brakes?

Did you install a full kit including front brakes components along with a matching booster/master combo?

If you feel you are having to apply too much effort into the braking, start with the basics. Purge air out of lines, starting with the longest line first, ( RR, LR, RF, LF ) If you've already done it, it doesn't hurt to try again. Sometimes air can get caught in one of the bends and it takes a few days to work it's way out.

If it wasn't a kit, you may have an undersized brake booster booster.
 
The ratio is changed through the bellcrank assembly that is sandwiched between the booster mounting brackets.
Manual discs use the same setup as drum, but take a ton of pedal effort to get the job done.
 
Ok. Ive got manual 4 wheel discs so guess I'm stuck with hard pedal effort. :( Think my cam is too radical for a booster set up. How much vacuum is required?
 
71Demon said:
Ok. Ive got manual 4 wheel discs so guess I'm stuck with hard pedal effort. :( Think my cam is too radical for a booster set up. How much vacuum is required?
Click to expand...

Run a 7/8" master cylinder. 4 wheels discs with manual will feel like power brakes.
 
roccodart440 said:
Run a 7/8" master cylinder. 4 wheels discs with manual will feel like power brakes.
Click to expand...
I`ve got a 87 dodge diplomat master cyl on mine, it`s a little more effort than I`d like. what mopar master cyl would be better for 4 wheel discs ?
 
whitepunkonnitro said:
The ratio is changed through the bellcrank assembly that is sandwiched between the booster mounting brackets.
Manual discs use the same setup as drum, but take a ton of pedal effort to get the job done.
Click to expand...

The hydraulic ratio determines how much leg is needed.
as suggested, use a small piston master ( less than 1") for manual discs and it will stop
easily with very little leg pressure.
 
As mentioned, the pedal and brackets are the same whether disk or drums, only the MC differs. Pedal ratio does vary between manual and power booster. The power setup requires more pedal effort (if no vacuum assist), which is why power MC's tend to have a smaller bore. That is due to the lever ratio in the power stand-off brackets. As mentioned, with either manual or power, you can decrease pedal effort by changing to a smaller MC bore.

I use a 7/8"D MC in all 3 old Mopars, 2 w/ power assist (for 95-99 Breeze, Cirrus, Stratus w/ ABS). Most here use a 15/16" D MC (80's Dodge trucks) for manual brakes, which you can buy as a ~$90 conversion from Dr. Diff. I would think front disks only or 4-wheel disks would be the same pedal effort, since with rear drums you proportion the rears down.
 
71Demon said:
I'll try that. I am currently using a 1 1/32 .
Click to expand...

Order a 73-75 A-body POWER brake 7/8" bore MC but run it manually. I guarantee you will like it. Less effort than a 1-3/32.

I have tried 1-1/8, 1-32 and 7/8 in my 68 cuda with manual 73-75 discs. The 7/8 bore is the way to go for most people.
 
KosmicKuda said:
Order a 73-75 A-body POWER brake 7/8" bore MC but run it manually. I guarantee you will like it. Less effort than a 1-3/32.

I have tried 1-1/8, 1-32 and 7/8 in my 68 cuda with manual 73-75 discs. The 7/8 bore is the way to go for most people.
Click to expand...
I think the 87diplomat master cyl is a small bore.
 
I love the 15/16" master cylinders from Dr. Diff. Great pedal feel, not a ton of effort, decent amount of travel to allow for better pedal modulation and brake control. That's what I run on my Duster, and I converted my Challenger over a few months ago from power disks to manual with the same 15/16" master. Better all around.

The only drawback I've encountered with them is the OE caps and seals, seems like after you take them off and tighten them back up more than 2 or 3 times they start leaking. But a quick replacement with Dorman parts and they work great.
 
1965t5 said:
If you go with the manual 4 wheel discs, do you need a prop valve in the system at all if starting with manual drum at all wheels?
Click to expand...
why? w/ the stock one, all wheels get the same just like before. -------?
 
1965t5 said:
If you go with the manual 4 wheel discs, do you need a prop valve in the system at all if starting with manual drum at all wheels?
Click to expand...


I didn't. I went from 4 wheel drum to 4 wheel disc.

If you did end up needing one it's easy enough to add one
 
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