Improving braking power after disc conversion

[Tonefiend]

My '70 Challenger with stock discs in front and an SSBC disc kit in the rear has the stock master cylinder without power brakes.

Frankly the stopping power sucks and is borderline dangerous for So Cal driving.

Sooo...  I have been trying to find out the best course of action to upgrade and improve braking.  I would like to do the easiest method with the best bang for the buck.

Would a beefier non assisted MC be a good idea?  Or adding a power assist?  Stock used, or aftermarket?   Relocating pedals and cutting the firewall does not seem like much fun, but if I have to I will. 

Thanks in advance for any and all advise!

[autoxcuda]

My '70 Challenger with stock discs in front and an SSBC disc kit in the rear has the stock master cylinder without power brakes.

Frankly the stopping power sucks and is borderline dangerous for So Cal driving.

Sooo...  I have been trying to find out the best course of action to upgrade and improve braking.  I would like to do the easiest method with the best bang for the buck.

Would a beefier non assisted MC be a good idea?  Or adding a power assist?  Stock used, or aftermarket?   Relocating pedals and cutting the firewall does not seem like much fun, but if I have to I will. 

Thanks in advance for any and all advise!

Did you have this issue before you added the rear disk brakes?

What type/brand pads are your running. There a some people who really don't like the effort of a the Firm Feel race type pads in the city. Then there are some that don't mind it. It's a lot of personal preference.

What master cylider diameter do you have?

I know someone on Moparts had this issue with the E-berg 1 1/8" bore master in a non power stock disk front and drum rear. He put on a Dr Diff 15/16 aluminum master and things were fine. But the pedal travel went up.

I have an old 1 1/32 MP master and a 340 A-body Barracuda with a stock converter. I like the short pedal travel, but it does take some leg effort. Waiting a two or three long light sequencies on a real long left turn pocket is sort of annoying.

[Tonefiend]

I am not sure of the MC. It's about the size of my fist,maybe a little larger, anyway it's pretty small!   I recently aquired the car so i am not yet that familiar with it.  It is a stock PS, AC, front discs, rear drums, 318, 904 trans with a small rear end. 7-1/4?  Converted to 8.75

I read in another thread some prefer the manual brakes. Now my question would be if I could just swap out a more powerful MC from a big block car?

[autoxcuda]

I am not sure of the MC. It's about the size of my fist,maybe a little larger, anyway it's pretty small!   I recently aquired the car so i am not yet that familiar with it.  It is a stock PS, AC, front discs, rear drums, 318, 904 trans with a small rear end. 7-1/4?  Converted to 8.75

I read in another thread some prefer the manual brakes. Now my question would be if I could just swap out a more powerful MC from a big block car?

The dimension I talked about is the bore of the piston inside the master cylinder. It relates to the hydraulic leverage in the system. There's nothing more powerful about the master cylinder in a big block car.

Have you had a car with manual drums or manual discs before??

Did you or the previous owner add the SSBC rear disks??

[brads70]

    Just learning...

[6packCuda]

Are you sure you're even getting braking at both the front and rear? You could have a torn piston in the MC causing either the front or rear brakes not to work at all.

[BIGSHCLUNK]

i've got manual brakes and NIKKI stops great. Granted its not the soft easy pedal that my Pontiac Has. I've got SSBC in the front with the SSBC (GM STYLE) master. But even before that she stopped OK. I'd really take a good look at things, maybe the rears are working and the fronts are not. That would make for really crappy brakes , much worse than the rears not working.

[Katfish]

Sounds like you've got a couple of issues going on.  I switched to larger rotors up front and used a manual MC from a 76 Dart and it works great.  Fronts do 70% of the braking, so you need to upgrade the fronts or the rear discs really won't be that much of a benefit.

Good read here:

http://www.moparaction.com/tech/archive/disc-main.html

[Tonefiend]

This is my first car with manual brakes.  I just got the car from a guy who started fixing it up but screwed everything he did up, so I am trying to sort out his problems.  He put the kit in then didn't install the locking pawl for the axles which screwed it up.  He then took it to a mechanic who spent 4 months trying to figure out what to do.  They didn't have the service manual, instruction manual for the kit that says in huge letters not to use the stock bearings and if you do you have to modify the brackets. 

I am not even sure if the front or back brakes are working or what is stopping the car.  I would assume the car would swap ends if the backs worked and the fronts didn't.  Also the E brake barely works. all that does is drag a little.  That may be an indication they dont work?

I guess it's a given I need to go through the system and check everything out.  My next question is do all master cylinders produce the same power?

*edit* Thanks Katfish that is a great and helpful article!

[Changin Gears]

  My next question is do all master cylinders produce the same power?

*edit* Thanks Katfish that is a great and helpful article!

It's not so much power as pressure.  A master cylinder with a 15/16" bore will make more line pressure than on with a 1 1/16" bore.  But you never get something for nothing, you will have more pedal travel with the 15/16".

What exactly is the problem?  too hard of a pedal, fronts locking 1st, pedal goes to the floor.....

[Tonefiend]

Just general the problem is weak braking.  You really have to push hard.    I do not know if I could lock up the brakes. Testing may be in order.  I don't have an issue with the travel although I would not mind less. 

There is also the possibility the braking is normal and I am not used to a car this heavy with manual brakes.  At any rate I would like to get a little more stopping power. 

[Changin Gears]

Just general the problem is weak braking.  You really have to push hard.    I do not know if I could lock up the brakes. Testing may be in order.  I don't have an issue with the travel although I would not mind less. 

There is also the possibility the braking is normal and I am not used to a car this heavy with manual brakes.  At any rate I would like to get a little more stopping power.

Well you could try a master cylinder with a 15/16" bore, assuming yours is bigger, or try to find some pads that are softer.

[Tonefiend]

Thanks for the help.  I will check everything out and see what bore I have then take it from there. 

[ragtopdodge]

stock proportioning valve?

Get an adjustable one.  Be sure to bleed the hell out of the brakes.

I had manual, 4-wheel drums in the GC I sold and it stopped/felt great after replacing the pads/wheel cylinders.  Felt even better than my wife's 300c SRT8 IMHO.

[HP2]

I guess the first thing I'd do is take a friend out to a dirt road and see if you can lock up all four wheels. If no, they you know which end you need to start looking in to, If yes, then move to the pavement and repeat the lock up test. You should be able to lock up all four wheels on pavement. It may take some effort, but not a huge amount. If you can't lock them up at all, I'd say it is a lack of pressure from the master cylinder. If it is only one end or the other, then we can start digging around at some other possibilities.