Brakes: Front Disc Brakes

[63looks59]

Is a Dual master cyl Required For front disc brake conversion OR
can the single master function just fine for front disc ????

[PackardV8]

Is a Dual master cyl Required For front disc brake conversion OR
can the single master function just fine for front disc ????

Short answer, yes. Studebaker built front disc brake cars with a single master cylinder.

Many here will write you're endangering yourself and everyone on the highway by venturing out with a single master cylinder. Your opinions and results may vary, but fact remains the single master cylinder worked well for forty years. It just isn't as idiot-proof as a dual. The single requires scrupulous maintenance, including flushing the system ever 2-3 years. Even though few owners ever did that, the single master cylinder failures were rare.

jack vines

[Gunslinger]

I can testify that single master cylinders do fail. It happened over thirty years ago when I had my '63 Avanti. I had just pulled out of a convenience store one morning about 6:30AM heading to the car dealer I was working at. The brake pedal went to the floor and no braking at all. It was very low speed and here was no traffic that time of the morning. I just let the car drift into the parking lot of where I worked and the car stopped when it slowly bumped into the curb...no damage of any kind. The car sat there while I ordered and received a master cylinder rebuild kit then once fixed it was fine.

Some years later after I sold the car and it passed through at least two owners I was able to locate the car and its owner. The car had repeated its history...the new owner had the car painted and when he returned home the master cylinder failed as he pulled into his garage and hit the tool cabinet and did $1800 in body damage to his just out of the body shop car. Deja' vu.

[thunderations]

The dual cylinder that is used is very inexpensive, pretty easy to plumb and gives excellent peace of mind. I converted my 66 Daytona with factory discs to the dual cylinder and it's great. I also replaced every steel and flex line, rebuilt the calibers and wheel cylinders. It stops good and straight.
The next conversion will be a Turner disc conversion to a drum brake 64 using the dual master cylinder. I know the 11" drum brakes were good, but the cost of new drums offsets the cost of the discs, plus, the discs are better.

[Bob Bryant]

A year ago my 1963 Avanti received a Turner dual master cylinder and front disc brake conversion. A good improvement.

[bensherb]

The conversion to a dual master on a Lark is super easy, no reason not to do it. It's more involved on a Hawk and other parts beyond just the cylinder and brake line are needed.

A single type master cylinder will work for any brake system if properly sized. I once had a four wheel disk system with four, 4 piston calipers and a single reservior master and it worked great. The brakes, calipers/wheel cylinders, don't know or care how many reserviors the master cylinder has. They only care that the bore is appropriatly sized and the reservior is of sufficient size to maintain fluid supply.

[sals54]

A matter yet to be addressed here in the use of a single master cylinder, (which I also used, trouble free for decades), is the check valve.
You must remove the check valve from the front of the master cylinder. Then install a 2 lb check for the front brakes and a 10 lb check for the rear brakes.
The front will keep enough pressure in the line to keep the brake pads close to the rotors. This is what gives the quick response for the pedal.
The rear is needed to keep the cups expanded in the wheel cylinder so it doesn't leak and maintains pressure.
If I've misspoke, someone will surely correct me.
But the check valves are indeed necessary.

[bensherb]

It could be just my experiance Sal, but I've never used any residual pressure valve in any brake system I've built and have never noted a need for one. You are very correct in that the residual valve needs to be removed from any master cylinder not originally intended for disk brake use. If not, the first time you step on the brake the disks will lock and not release.

[oilnsteel]

A nice advantage of having to grease everything at 1000 mile intervals is that you get to inspect the brake and suspension to help avoid embarrassing failures.

JT

[63looks59]

Thank U all-----I get it that Hydraulics are just that---no matter how many reserviors----yet I have heard since I have been
interested in this, of a few single cyl failures---seems although not frequent by any means----it may be not... Rare
so I think I am going to go with the dual--- and later a disc conversion----
I want to THANK YOU ALL FOR YOUR EXPERTISE

[sals54]

It could be just my experiance Sal, but I've never used any residual pressure valve in any brake system I've built and have never noted a need for one. You are very correct in that the residual valve needs to be removed from any master cylinder not originally intended for disk brake use. If not, the first time you step on the brake the disks will lock and not release.

While I'm sure it's possible to have the system work that way, I've always used the 2# and 10# checks in my systems. Never had a problem

[studegary]

Is a Dual master cyl Required For front disc brake conversion OR
can the single master function just fine for front disc ????

If you have drum brakes now and you are referring to "63looks59", you already have a factory dual master cylinder.

[jimmijim8]

I can testify that single master cylinders do fail. It happened over thirty years ago when I had my '63 Avanti. I had just pulled out of a convenience store one morning about 6:30AM heading to the car dealer I was working at. The brake pedal went to the floor and no braking at all. It was very low speed and here was no traffic that time of the morning. I just let the car drift into the parking lot of where I worked and the car stopped when it slowly bumped into the curb...no damage of any kind. The car sat there while I ordered and received a master cylinder rebuild kit then once fixed it was fine.

Some years later after I sold the car and it passed through at least two owners I was able to locate the car and its owner. The car had repeated its history...the new owner had the car painted and when he returned home the master cylinder failed as he pulled into his garage and hit the tool cabinet and did $1800 in body damage to his just out of the body shop car. Deja' vu.

Don't put new guts in an old master cylinder. They are available brand new very reasonably priced at bout 50.00 jimmijim

[52 Ragtop]

Yes, a single M/C will work! BUT, you must either use a diac brake M/C or remove the residual check valve in the drum M/C. Otherwise, you will get "about" 3-4 miles or so, before the brakes lock up! (don't sk how I know) <G>

The stock M/C has a 10# residual check valve built in, disc brakes use a 2# check valve. Why not go with a dual M/C? it IS a safety issue!

Jim

[Hawklover]

Sal....the single master cyl that was on my Avanti for almost 50 years never had a check valve! As you know the front Dunlop cylinders are 2 and 1/8...the rears 3/4.....this was done to prevent rear wheel brake lockup! The only thing I have added to my car is a Master Power hold off valve, to allow the the rear shoes to be applied slightly before the front pads begin to engage, thus preventing some nose dive. Additionally I put in a two chamber M/C with the same bore as the single, so I would have the same pedal feel.

A matter yet to be addressed here in the use of a single master cylinder, (which I also used, trouble free for decades), is the check valve.
You must remove the check valve from the front of the master cylinder. Then install a 2 lb check for the front brakes and a 10 lb check for the rear brakes.
The front will keep enough pressure in the line to keep the brake pads close to the rotors. This is what gives the quick response for the pedal.
The rear is needed to keep the cups expanded in the wheel cylinder so it doesn't leak and maintains pressure.
If I've misspoke, someone will surely correct me.
But the check valves are indeed necessary.