Manual brakes are scary

[Ron H]

You know if the set up was a kit conversion or from another ride? What I have on mine is from SSBC and is a GM set up (I added power). Had issues with one reservoir in the MC not cooperating from a 3rd bench bleed buying another for; they’re not pricy. Mid-60’s era Vette MC with my kit. Non-lock can indicate air trapped in the system or in the MC, TWO different issues. Or maybe just playing with the prop valve adjustment. As posted, MC bore sizes are different btw power and manual.

 

[hunt2elk]

Very sorry—-I’m on my iPad & it seems I’m all thumbs

It wasn't you, but srw-409. You are doing everything perfect.

 

[AC64]

Aftermarket conversion ?Brand/type. How complete ? calipers, prop valve, master, brake size front/rear? Trying to get more details on what you have to help with diagnosis. More info, better help.

Pulled the wheels today——-fronts are 3880 585s , large single piston caliper & the rear drums are standard 11 in drums. Master is I believe a drum / drum unit only 7 in from mount base to end to keep it from hitting the high rise exhaust manifold on the max wedge app. Brake pedal is a PB type & I‘m not sure if the pedal geometry is the same as the manual brake type.

 

[mopar 3 B]

It wasn't you, but srw-409. You are doing everything perfect.

Maybe the 409 says it all.

 

[dadsbee]

Easy bump scrolling on a phone... icon is in a bad place.

 

[srw-409]

@srw-409. You will have to explain the big red "X" for a simple statement I made that is indeed a fact.

My apologies @hunt2elk, touch screen malfunction on my part. In fact I sourced a 15/16” for my own conversion.

 

[casey henson]

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.

 

[MoparLeo]

So far the Master cylinder is wrong type. That can be a major factor. Make sure rear shoes are adjusted up tight and all air is out of the system. Braided lines up front also help prevent hose welling under braking which will give a softer pedal.
Since it was a single line car originally was the system split properly and have the hard lines been replaced ?
Another thing is knowing what type of friction materials the pads and shoes are made of. Semi metallic's need heat to stop and are very hard to modulate when the lining is cold.

 

[Don Frelier]

If you don't have one already you may want to find/make a heat shield for the master cylinder as it sits literally right above the exhaust manifold.
I would recommend a silicone based fluid as well.

 

[AC64]

I use a 15/16" master on all 3 of my manual disc/drum cars as well. They all stop a lot better than you are describing.

Is there a particular proportioning valve that you have found success with?

 

[AC64]

If you don't have one already you may want to find/make a heat shield for the master cylinder as it sits literally right above the exhaust manifold.
I would recommend a silicone based fluid as well.

Thanks—I have wrapped the factory exhaust manifolds and the end of the MC is close to touching. Just about 1/2 in

 

[AC64]

So far the Master cylinder is wrong type. That can be a major factor. Make sure rear shoes are adjusted up tight and all air is out of the system. Braided lines up front also help prevent hose welling under braking which will give a softer pedal.
Since it was a single line car originally was the system split properly and have the hard lines been replaced ?
Another thing is knowing what type of friction materials the pads and shoes are made of. Semi metallic's need heat to stop and are very hard to modulate when the lining is cold.

Great info—all will need to checked. I have always chosen organic shoes & pads when available, even though they need to be changed more frequently. They provide a better feel & generally don’t glaze as much as the harder compounds. I think I am going to find that I have a proportioning valve problem & was only getting front brakes. I think I could have gotten better braking by dragging my feet

 

[Ron H]

You have a gravelly, sandy road or driveway nearby? Mark the location of the prop valve and count the number of turns C and CCW you turn it so you know where you started. Take it on the road and hit the brakes (better if you have a buddy outside watching the car to view what tires are skidding and on each side). Doesn’t require much speed, around 25MPH. If the rears lockup and not the front, readjust the valve to increase line pressure to the front. Yeah, some playing without having a line pressure gauge. As posted, if skidding isn’t possible, decent bet to verify is air trapped in the system or in the MC. If you bled the brakes, you would likely have ID’d a good or poor flow of fluid from each wheel. Make sure the rear drums are set right. Also verify that the bleeders on the calipers are on ‘top’. Just throwing out some things you may already know. But, when you mentioned you can stand on the brakes and get no hard braking often is indication of trapped air.

 

[Ranger16]

I've had lots of cars with manual brakes including a manual 4 wheel drums on a 10.60 car that stopped just fine

I have to agree with Cranky. I have original 4 wheel drums. I can and have locked them up. Can't ask for much more than that.

 

[mopar 3 B]

Yea but, yea but. Fixing the manuals doesn't leave room for a disc brake screwup. Now what was the reason for installing dick brakes on the front? Oh, yea I needed hard pedal and no brakes. Just kidding. Hope you figure it out.

 

[Kern Dog]

More than likely a bad case of 'Fat fingers' - the guy has been here 13 years, and has made 65 posts in that time.....not really what you'd call a solid contributor.

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

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.

 

[hunt2elk]

Is there a particular proportioning valve that you have found success with?

I get mine from Cass aka Dr. Diff. I can't remember where he told me he gets them from. You probably do have something not quite right in your setup, but another thing is that all these new pads and shoes don't seem to work the greatest right away. They need to get broke in before they grab good. Unlike the old asbestos stuff.

 

[AC64]

You have a gravelly, sandy road or driveway nearby? Mark the location of the prop valve and count the number of turns C and CCW you turn it so you know where you started. Take it on the road and hit the brakes (better if you have a buddy outside watching the car to view what tires are skidding and on each side). Doesn’t require much speed, around 25MPH. If the rears lockup and not the front, readjust the valve to increase line pressure to the front. Yeah, some playing without having a line pressure gauge. As posted, if skidding isn’t possible, decent bet to verify is air trapped in the system or in the MC. If you bled the brakes, you would likely have ID’d a good or poor flow of fluid from each wheel. Make sure the rear drums are set right. Also verify that the bleeders on the calipers are on ‘top’. Just throwing out some things you may already know. But, when you mentioned you can stand on the brakes and get no hard braking often is indication of trapped air.

Thanks Ron—trapped air could be a problem, but I get approx. 1 in of travel in the pedal & it goes no further hard as a rock with no softness in the pedal & slows the pace of the car but even two feet on the pedal will not lock up front or back. I think I will get a line pressure gauge to determine how much pressure the MC is generating

 

[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.

Thanks for your thoughts—— I wish I could add a booster or a hydro boost, but on the max wedge those high rise manifolds restrict you to a 7 in MC without hitting the manifold & the engine creates about 1 in of vacuum so you can’t use a vacuum booster.

 

[kiwigtx]

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

We know.