Manual brakes are scary

[AC64]

and don't forget manual brake cars need more leverage at the pedal. 6:1 ratio or better for manual which means the top hole on the brake pedal if it has two. the two main items for more power on manual brakes. master bore diameter and pedal ratio.

Thanks Casey—-I mentioned that in a post yesterday. You need to move the MC pushrod up toward the pivot point on a manual system to create greater pressure on the MC piston. Not as much travel, but a higher level of pressure. If you have 3 or 4 inches of unused travel I would assume you could double your brake line pressure.

 

[Billccm]

Manual Disc conversion video:
Project BeepBeep - 68 RoadRunner Disc Brake Conversion - FINAL CHAPTER! -

Watch both videos.

 

[Geoff 2]

Post #41. The travel of the MC p'rod will be the same if you move it up to the 'manual' hole position. The pedal travel will now be more, not less.

 

[AC64]

Manual Disc conversion video:
Project BeepBeep - 68 RoadRunner Disc Brake Conversion - FINAL CHAPTER! -

Watch both videos.

Was that conversion on a manual brake car or a booster car?

 

[Billccm]

Was that conversion on a manual brake car or a booster car?

The car was manual drums. I went with the Dr Diff conversion 15/16 master cylinder. It stops really well.

 

[AC64]

Post #41. The travel of the MC p'rod will be the same if you move it up to the 'manual' hole position. The pedal travel will now be more, not less.

Correct—-what my thought is that if your brake pedal travel is only about an inch you will create more foot pressure by moving the rod attachment point closer to the pedal pivot point. Offset is you increase pedal travel

 

[AC64]

I've made more than 65 posts in one night.

View attachment 1336406

I had this same brake issue in 2012.
I wanted to switch from power brakes to manual for the sake of simplicity. I had 12" front discs and 10.7" rear discs. I tried a 1 1/8" bore, a 1 1/32" and 2 that were 15/16" and all of them gave a firm pedal with terrible braking.....it was as if whatever the pedal was sending was not getting to the wheels. I could barely skid on gravel. I put the power booster back on and later noticed that I had a disc/drum proportioning valve in....with the 4 wheel disc setup! The Prop valve reduces rear pressure in disc/drum systems to avoid lockup and was rendering the rear brakes almost ineffective. The power booster was masking the problem.
Here we are, years later and I'm in the process of upgrading to bigger rotors and adding a hydroboost unit.
Good luck to you.

 

[AC64]

I've made more than 65 posts in one night.

View attachment 1336406

I had this same brake issue in 2012.
I wanted to switch from power brakes to manual for the sake of simplicity. I had 12" front discs and 10.7" rear discs. I tried a 1 1/8" bore, a 1 1/32" and 2 that were 15/16" and all of them gave a firm pedal with terrible braking.....it was as if whatever the pedal was sending was not getting to the wheels. I could barely skid on gravel. I put the power booster back on and later noticed that I had a disc/drum proportioning valve in....with the 4 wheel disc setup! The Prop valve reduces rear pressure in disc/drum systems to avoid lockup and was rendering the rear brakes almost ineffective. The power booster was masking the problem.
Here we are, years later and I'm in the process of upgrading to bigger rotors and adding a hydroboost unit.
Good luck to you.

If I can’t improve manual braking I will go to a hydro boost system. Somewhere along the line I was told that they had seen a hydro system with it being installed inside the firewall. If so that would be great as I have only about 7 inches from the firewall to the exhaust manifold

 

[Ron H]

Your ride have power steering?

 

[AC64]

Your ride have power steering?

No Ron----It is a manual brake & steering car. I thought the steering would be a greater problem than the brakes, but the ratio in the manual box steering makes it relatively easy to steer even with the added weight of the RB, the cast iron cross ram, and the high rise cast exhaust. Brakes are another story-------really doesn't stop, they just slow you down a little.

 

[Geoff 2]

Because of the high line pressure reqd with disc brakes, it always surprised me that street driven cars could be sold with un-boosted brakes. An accident waiting to happen...

 

[Ron H]

No Ron----It is a manual brake & steering car. I thought the steering would be a greater problem than the brakes, but the ratio in the manual box steering makes it relatively easy to steer even with the added weight of the RB, the cast iron cross ram, and the high rise cast exhaust. Brakes are another story-------really doesn't stop, they just slow you down a little.

Reason I asked is hydroboosts I'm aware of link to the power steering pump. I'm sure there are other tricks members can inform about. But you shouldn't need to go this route, there's a demon in your system to identify and good posts on hunting it down.

 

[lyndondb]

So how is a mc 15/16 identified. All the ones I look at aren't specifying the bore.

 

[Billccm]

This thread might help

Master cylinder for disc brake conversion

Is there a master cylinder for manual disc brakes in size 15/16 " bore size that looks kinda stock for a late 60s or early 70s B body . with Manual disc brakes ? OR is there even an option besides the plastic bodied version like late models Smallest I can find is 1-1/16" bore

www.forbbodiesonly.com

 

[bc3j]

My brakes are manual. I used all Mopar source parts for the brakes, 1.031 master from Dr Diff, 11.75” rotors, semi-metallic pads and the car stops just like my Acura. No problems.

 

[RemCharger]

Maybe I missed it, but are you using a PB pedal or a manual brake pedal.

 

[dangina]

running manual brakes with 13" rotors/brembo calipers front, 12" rotors/cobra calipers rear, 15/16" master cylinder and a adjustable bias for the rears, love this setup would never go back to power

 

[Kern Dog]

Because of the high line pressure reqd with disc brakes, it always surprised me that street driven cars could be sold with un-boosted brakes. An accident waiting to happen...

Why? I personally own 2 manual disc/drum A body cars that stop as well or better than new cars.

 

[Cranky]

Why? I personally own 2 manual disc/drum A body cars that stop as well or better than new cars.

Only manual disc brake vehicle I've had was a 74 D100 pickup. It was light duty but carried and pulled some decent loads with it and it stopped fine.

 

[diesel_lv]

Because of the high line pressure reqd with disc brakes, it always surprised me that street driven cars could be sold with un-boosted brakes. An accident waiting to happen...

My '67 4dr has manual disc/drums. 15/16" master cylinder. My 110lb daughter can stop it easily w no leg strain. Pressure is developed w the proper master cylinder, brake lever length n pivot point for leverage. Mine was designed for manual so it works perfect.