Bigger Bore Vacuum M/cyl Q

[Jimn8or]

I remember reading once about a m/cyl with a bigger bore for those with vacuum brakes. I have a friend who has just done the Baer 4 wheel conversion and he needs more force/master cyl.
Can anyone help me with p/n's or applications?
Thanks for all replies,
Jim

 

[gofstbuick]

The bore need to be smaller, because it will create more pressure in a smaller area than a larger area. The brake pedal provides the force and that is a constant. So if the force is constant, then the same force applied to a smaller area will generate more pressure.

 

[Turbo6inKY]

Originally posted by gofstbuick
The bore need to be smaller, because it will create more pressure in a smaller area than a larger area. The brake pedal provides the force and that is a constant. So if the force is constant, then the same force applied to a smaller area will generate more pressure.

Smaller bore would mean greater pressure, but I fear the guy might be running into a problem not of pressure, but of volume. it takes a lot more fluid to clamp those big Baer calipers than the stock single piston jobbies. He'd need a bigger bore master cylinder to move more fluid.

Has he talked to Baer about what he should do? That is supposed to be a bolt-on kit using the factory master cylinder. Are you sure the system was bled properly after the installation?

 

[Silver 6]

I believe if you check on the 78-80 master cylinders you will find they had a larger bore than the ones for the 81-87 in the Regals.

 

[Red Regal T]

You can get BBody Master cylinders with the big bore from early 80s full size cars such as Olds 98 and Caddies. Cadillac full size rear drive cars were made into the early 90s. They look just like a Regal MC, though reservoir is a little bigger and the bore is larger. At one time I installed a BBody master cylinder on my T equipped with vacuum brakes and my first impression after the install was the brakes were a tad better.

 

[Spdrcer34]

The 78-81 Master Cylinders are cast iron. Other years are hit and miss for the Aluminum or Steel ones.

While doing the 1LE brake upgrade, I also had to swap out my PERFECTLY GOOD Brake Booster because the 1.125" B-body master cylinder wouldn't even bolt-up to the booster because the bore is SO much smaller......

Ryan

 

[bruce]

What makes you think things are in fact wrong?.

Have you tried calling/writting Baer?.

Dave Morgan's book Doorslammers has an interesting chapter on brakes.

 

[Jimn8or]

Thanks for the replies. I am waiting for word back from Baer still. Although the brakes function properly, they do not seem to have the stopping power of the oem's? My friend says that he couldn't skid a tire with a hydrolic press applying the brakes, thus my querey about a larger bore m/cyl. Hopefully, between what has been suggested here, and word from Baer it'll all work out OK.
Jim

 

[Red Regal T]

Originally posted by Red Regal T
You can get BBody Master cylinders with the big bore from early 80s full size cars such as Olds 98 and Caddies. Cadillac full size rear drive cars were made into the early 90s. They look just like a Regal MC, though reservoir is a little bigger and the bore is larger. At one time I installed a BBody master cylinder on my T equipped with vacuum brakes and my first impression after the install was the brakes were a tad better.

99% of these described above are the aluminum bodied master cylinders. Also, same years as above, Buick Electras, park avs, Olds Delta 88s, sedans, cpes, and station wagons............rear drive models. You have to look real hard to find a cast iron mastercylinder.

 

[bruce]

Originally posted by Jimn8or
Thanks for the replies. I am waiting for word back from Baer still. Although the brakes function properly, they do not seem to have the stopping power of the oem's? My friend says that he couldn't skid a tire with a hydrolic press applying the brakes, thus my querey about a larger bore m/cyl. Hopefully, between what has been suggested here, and word from Baer it'll all work out OK.

Well designed and optimised brakes don't have the miserable characteristics of the stock setups. They work really well without all the fan fare of premature lockup, and poor brake bias.

Being able to easily lock up the brakes just shows how out of balance the system is.

In a HUGE wet/damp parking lot, you should just have the front end just start to lock. Please don't attmept this on a street for the first test of wheither the system will lock up.

If it's the high effort, that's bothering, then you want a smaller M/C, or to increase the pedal leverage.

FWIW, folks are so used to, or wanting of a light brake pedal that, it's just about necessary to have ABS since there is so little feedback thur the pedal. The higher effort allows for being better able to modulate the amount of braking being done. Since the pedal is not so much of an off/on switch.

 

[Turbo6inKY]

Originally posted by bruce

Being able to easily lock up the brakes just shows how out of balance the system is.

Or how crappy your tires are. Did your buddy upgrade the rubber when he did the brakes?

 

[WHITE T]

Hey Guys!

Just caught this thread.

A bigger bore master is not required or recommended. All our (Baer) G-body systems are designed to work with the factory master. What was stated earlier is correct, when you increase the bore diameter you increase volume and decrease pressure. What will end up happening is that the pedal will get even harder and firmer, and depending how large you go the car will basically act like a low vacuum situation (hard pedal rolls to a stop).

How many miles are on the vehicle? Keep in mind that when the rotors are "green" (new) we really stress the fact we don't like to see customers trying to lock the brakes up to see how well they work. The rotors need some time put on them, then they need to be seasoned and bedded (all information is included with the system). These instructions are very important, and they help heat cycle the rotors, and make them stronger. Keep in mind the weakest time in a rotors life is when it is new. These brakes will get much better once the rotors are seasoned and the pads bedded.

Hope this helps, if the pedal is nice and firm I would recommend driving it around for awhile and put some miles on it.

Any questions feel free to contact me!
Rick Elam
Baer Brake Systems
(602) 233-1411 ext 24

 

[Red Regal T]

Originally posted by Red Regal T
At one time I installed a BBody master cylinder on my T equipped with vacuum brakes and my first impression after the install was the brakes were a tad better.

Just to clarify, I did this swap on my car with stock brakes. The reason I did it was to see what happened and to settle the question in my mind whether a B-body MC would help or hurt my application. On my car, at that time, it made my pedal feel a little better. I wouldn't say it was necessary. In fact, I returned to a nicer cosmetically, correct size master cylinder after thousands of miles on the B-body unit.