Brake Master Cyl. ?

[rcf925]

I'm working on my 68 and have got to the brakes. My car doesn't have the tandem braking system with the 5 lines going to the master, I only have 3 , 2 to the front, 1 to the rear but my master has 5 holes. Should I just plug up the extra two or is there some way to use them without running more brake lines

[Hans]

The master was there when  you got the car?

[Son of Marty]

Basically no you need to run the brake lines to the front calipers or plug them ether way run the rear brakes off the other end of the master than the fronts to maintain some degree of redundancy.  

[TobyB]

How many circuits do the front calipers have?

 

You probably just have the wrong master- 68 brakes are different.

 

and tiny.

 

t

[rcf925]

12 hours ago, TobyB said:

How many circuits do the front calipers have?

 

You probably just have the wrong master- 68 brakes are different.

 

and tiny.

 

t

This is the master I got with the car, I know it's probably later tandem but I only have the 3 lines to it. I do have upgraded bigger vented rotors and calipers on the front I'm going to use. If I can just plug 2 and use this would be the simplest, I've been looking for 68 Master with no luck

[rcf925]

Just went through my parts, What I have is a upgraded bigger volvo single line calipers like IE uses with the vented rotors. 

[jimk]

Brake operating fluid is classed as an incompressible fluid.  What happens in the MC when a port is blocked and the other ports have fluid flow to the calipers/wheel cylinders?

When the fluid to the blocked ports does not move, does the brake pedal go firm and the connected brakes not operate?

Let's hear it.  I don't know the answer.  This is a safety system, should it be messed with?

[rcf925]

46 minutes ago, jimk said:

Brake operating fluid is classed as an incompressible fluid.  What happens in the MC when a port is blocked and the other ports have fluid flow to the calipers/wheel cylinders?

When the fluid to the blocked ports does not move, does the brake pedal go firm and the connected brakes not operate?

Let's hear it.  I don't know the answer.  This is a safety system, should it be messed with?

The way a tandem master works if the piston going to the front of the cylinder that normally operates front and rear lines ( The 3 I have) fails and goes to far in the bore thats when the 2 tandem lines going to front operate so when brakes are working normally the tandem lines aren't used, That's why I was thinking of plugging. If my brakes did fail you always have the emergency brake. That's my understanding

[Hans]

Depends on brake system configuration. An 02 with tandem system  - if memory serves - had half the MC doing two of four front pistons, the other half did rears plus other two front pistons. This meant you'd have half the system working if one side failed. I'm not sure what would happen if you plugged one half and used just the other for three out lines; but I think it would unbalance the MC. With bigger calipers, maybe the E21 MC will work. Check Rockauto.. 

[rcf925]

19 minutes ago, Hans said:

Depends on brake system configuration. An 02 with tandem system  - if memory serves - had half the MC doing two of four front pistons, the other half did rears plus other two front pistons. This meant you'd have half the system working if one side failed. I'm not sure what would happen if you plugged one half and used just the other for three out lines; but I think it would unbalance the MC. With bigger calipers, maybe the E21 MC will work. Check Rockauto.. 

Front 3 lines go to front and rear, back 2 are the 2 to front in case of failure. I like your E21 Idea, I think I'll check into that

[Simeon]

3 hours ago, rcf925 said:

Just went through my parts, What I have is a upgraded bigger volvo single line calipers like IE uses with the vented rotors. 

 

The Volvo calipers are dual circuit. 

[TobyB]

Quote

If my brakes did fail you always have the emergency brake

 

Which you can tear out of the floor right before you plunge off the cliff.

The 'emergency' brake is good (almost) enough to hold the car on a slight incline.

If you split the brakes front/ rear on the 2 master circuits, you have

some redundancy- many earlier cars split it diagonally, which would be

scary, too.  But meet the letter of the law.

 

Yes, IF it would fit, the 5- port can have 1 port of each circuit plugged,

but make sure it physically fits into the car first- the 3- port brakes are 

mechanically quite different from the cars that have 5 ports... usually... in my limited experience.

 

If you're going to go to big brakes, I can heartily recommend duplicating the later

cars' 5 circuit system- it's very, very safe.  A bit more work up front, and maybe

some cost, but once it's done, you have what everyone has, and parts, etc, are easy.

'inventing' something with Volvo brakes for an early car leaves you with something pretty unique.

Others have used 320 calipers on early cars, since they are single circuit.

 

hth, and keep the questions coming,

t

 

[Hans]

"Front 3 lines go to front and rear, back 2 are the 2 to front in case of failure".....

I think you'll find that all five ports and lines are being used. The idea is that if one piston, or cylinder, or brake line leaks, the other half of the system will at least function until you get to a garage. As Toby says, it may be better to stick to  something proven. And I wouldn't trust the hand brake to stop the car from any speed in a straight line. The size of the MC should be matched to the size of the calipers and pistons, which you can see by perusing the shop manual specs. Using the E21 MC has been discussed here in the past.

[rcf925]

34 minutes ago, Simeon said:

 

The Volvo calipers are dual circuit. 

The ones I have are single line

[TobyB]

Ooo post a picture.  

the US 240s all were 2 circuit, that I found.  

You may have something different.   Or a Volvo caliper

that I've not come across-

(from a 140?)

 

-because-

 

I would really like

to find a 1 circuit 4 pot NON-VENTED

caliper with the 3" mount flange

Volvo geometry- it'd make

Datsun roadster big front calipers a lot easier.

 

Early 6ers and some 5's have a single circuit 4- pot-

but they have a 3.5" bolt spacing, which fits the tii strut.

 

 

t