Disc Brakes

[curtiswyant]

Kinda seems silly to upgrade to discs and keep that old single pot master cylinder. I'd upgrade to a dual chamber master before adding discs. My two cents

[55 Fargo]

It may seem like it and in all probability, a dual would be a better piece of equipment.

Having said that, there are many cars on here with or without disc, with only a very well maintained single jug MC.

These single jug MCs were used till about 1967 with most auto manufacturers, was there a lot of malfunction and/or accidents because of this, what was it like then. I had a number of vehicles with single jug MCs, never had an issue,at least that I was aware of.

These are some of the vehicles I had with single jug MCs, 63 Pontiac, 64 Chevy 2, 65 Impala SS Convertable(not sure if that was single or not), 64 Chev 1/2 ton, 65 Chev 1/2 ton, 66 Chev 1/2 ton, 55 Pontiac, 60 Chev Impala.

I never had a failure on these, but I did get in accident with a friend in his 70 Cougar, because of the MC. I also had a brake failure on a poorly maintained 1990 Nissan 240, the rear calipre started to leak. I als had brake faiure on cold winter night with my 1970 Pontiac Lemans, the front right brake hose started to leak.

I am pondering all of these things myself, currently my brakes are stock, they are new, but 1 rear wheel cyl has a slight leak, plan to replace before spring. But if the fronts start leaking it will be disc brake conversion, end of subject.

I find these brakes not bad, wouldn't want a panic stop at 50 and above, but my legs are strong, I would no doubt push out the brake fluid somehow, by jamming my foot down too hard, but maybe not, I would at this point cuz the back wheel cyl has a slight leak now.

I am running Dot 5 , I am happy with this product so far........Fred

[Norm's Coupe]

I've driven and owned several cars with just a single pot MC in the old days. Never had a problem with any of them. That's all they had then. As Fred points out, you really don't have that much of a problem with them if you pay attention to the vehicle and what it's telling you when you drive it.

Master cylinders and wheel cylinders very seldom just all of a sudden stop working. Most of the time when they start going bad, if you pay attention to your vehicle while driving, you will start to notice a pedal that is softer, or it goes further to the floor when you stop. When that happens, your car is telling you it's not feeling well in the brake system and needs to be seen by a doctor (mechanic). If you ignore it, then it will all of sudden one day stop working. So.....when the pedal needs pumping, or is soft, it's time to be checking for leaks somewhere in the system. Do that and you shouldn't have a problem stopping the car when you need to.

All that said, I've only had one master cylinder go bad on me in all my life. Interestingly that was a more modern dual master cylinder. So, dual master cylinders can also go bad. When it went bad, I was able to stop the car. However since the car was an automatic, the pull of the engine and the slow sinking of the master cylinder did allow the car to move forward.

All the above not only relates to master cylinders and brake systems. But........if you are really driving a car and paying attention to it, it will also usually tell you when something else is about ready to take a dump too. You shouldn't just turn the key on and drive. You have to pay attention, and not just to the road.

[PatS....]

The only master cylinder problems I have had were with dual chamber units and in all cases I lost all the brakes. Not once was I left with even some braking as is the supposed reason behind the dual unit.

So, while I'd like to have a dual unit, it isn't top of my list because the only ones that haven't let me down are the singles and the duals haven't worked as advertised.

[Guest Paul G (Dr Vinyl)]

The purpose of a residual check valve is to keep pressure in the system to keep the wheel cyl cups from leaking. Since discs do not have "cups" a very low, or even NO, residual pressure is need in the line.

In my opinion, if you use a single jug MC the system should be plumbed in such a way to maintain a residual pressure to the rears and little residual to the front discs.

Paul

[PatS....]

Some brake basics:

http://ecihotrodbrakes.com/brake_facts.html

[Norm's Coupe]

For those who feel they now have brake drag with the disc brake conversion, read the following. It was copied from the ECI web site.

10 PSI Valves - These valves are used in a drum brake system to prevent air from being ingested into the hydraulic system when you release the brake pedal. Typical wheel cylinder seals only seal when there is pressure behind them. Rapid release of the brake pedal creates a vacuum in the system which causes the seals to relax and air is ingested into the wheel cylinders. Maintaining 10 PSI in the system at all times prevents this. Some disc/drum master cylinders have 10 PSI residual pressure valves installed internally, some don't. If you're not sure, call us and we can tell you how to check. Also, some new style wheel cylinders have cup expanders which negate the need for the residual pressure valve. Either way, if you are not sure whether you have one or not, put one in. They are not cumulative and it won't hurt anything if you have two. Don't worry about brake drag, it takes roughly 75 PSI to overcome the return springs.

[Paul Beard]

The older fellow at my local napa told me the valve in the old MC is a one way valve to keep the fluid from flowing back into the MC. This was needed because the MC is below the wheel cylinders. I have no residual valves just proportioning valve. I will add residual valves when I am able to find a MC that fits between the cross member and the steering gear box not before do not want to drill extra holes only 1/2 inch forward of orig. mounting holes for steering gear box. My brakes are working fine and with the proportioning valve adjusted just right the rear brakes lock just before the front as per inst. that came with prop. valve.