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Brakes

[wilson pickett]

Duck Fat Sally......

You know you gotta slow......that Kay Five down.


[/wilson pickett]

:D
 
question

greg,

you seem to be a fan of math and science... i ran a single 3/16 line to the back. with my artsy understanding of hydrlics and all things brakey, is this bad?

x volume on one end = x on the other. just increased velocity?
 
Chef,

I'm not an expert in hydraulics (yet) but my understanding is that a larger line will require more fluid to move to create the same amount of motion in the rear calipers, which will typically require a larger amount of movement in the piston (brake pedal) to build equivalent pressure in the rear brakes.

I bought the Fred Puhn book, "The Brake Handbook" which explains all this stuff, but since I haven't gotten to this phase of my build yet I haven't spend much time reading it.

I'll bet that some simple Google searches on "hydraulics" or "Hydraulic brakes" could get you some basic information about how to calculate mechanical advantage with various sized pistons, lines, etc. :thinking:


:usaflag:
 
Actually I've read that a larger supply line diameter will not require a change of the piston. All you've done is increased the amount of fluid in the system, your piston will still give the same amount of pressure to the rear caliper.
 
That makes sense....it will only take extra fluid if the piston in the caliper is larger or has a longer stroke than before.

As you said, when the lines are full....they're full. A larger diameter line won't add any benefit, but it won't hurt anything either.


:usaflag:
 
If i'm not mistaken a larger line will require more force to move the caliper piston the same distance since the surface area (of the brake line) is now larger.

Lets think about hydro assist steering, a larger bore ram moves slower but with more power. In the case of a brake line it will be the opposite since the caliper piston is not changing bore size only the line leading to it.
 
Scott,

I think the only thing that really matters is the size of the piston on either end.

The psi that is generated at the pedal is transferred through the fluid and then applied to whatever surface area on the caliper side.

In the example of a hydro-ram, the reason the larger ram has more "power" is because the surface area of the ram's piston area is larger... so whatever PSI is being generated is being applied to a larger number of square inches on the back of that piston to push the rod out.

:thinking:


:usaflag:
 
Hey Greg, You running 4 wheel discs? Same question for you Chef.

If you are, did that Summit pro-p valve fix the bias issues for the 4 wheel discs?

Thanks!
 
Greg, for a perfect example turn your garden hose on (without a nossle on the end) and then pinch the hose (creating a smaller hose diameter) and see what happens. With the hose pinched you will have more pressure.
 
I think the analogy would be more appropriate if you left the nozzle attached... :thinking:

Since the brakes are a "closed system" there isn't any flow, only pressure generated by the brake pedal (or in the water hose analogy, pressure from the city water source) pushing against the closed hose nozzle.


Geez, if this discussion gets any more heated I'm going to have to actually pull my brake book off the shelf and read it... :D


:usaflag:
 
wilwood

Alright so I called a tech at wilwood and they recommend 3/16 hardlines for everything, and the pressure stays the same it's just the velocity of the fluid in the line that changes with smaller lines.

cheyenneK20, 4 wheel disc and the proportioning valve works like a champ.
 
I think I'm running 3/16" hardline to my rear brakes as well. I've got 1/8" to each wheel at the back though. Everything seems to work fine.
 
bp71k5 said:
I think I'm running 3/16" hardline to my rear brakes as well. I've got 1/8" to each wheel at the back though. Everything seems to work fine.
Click to expand...

The smallest brake line is 3/16" then goes up from there UNLESS you have something totally custom.
 
The smallest brake line is 3/16"
Click to expand...

Hmm, it looks like you're right about that. After looking at it, the brake line down the rail and the rear appears to be the same and measure 3/16" OD. I was confusing it with the fuel return line which is 5/16".
 
In my build thread you can see that I am using all the lines (Brake/Fuel) from my 90. The 90 came with 1/4" line for the rear and 3/16" for the front. The 1/4" line ran from the Master Cyl. all the way to the Flex T in the back and then 3/16" on the axle to the Wheel Cyl. I bought the same Dist Block with prop valve that Chefbear bought. Except my is stamped SSBC.

I also found a great place for Brake lines and parts. I will post it up in my build thread.

If anyone is looking for a good double flare kit. Spend the money and get one from Rigid. My flares look as good or better than factory. I have used cheap ones in the past and it showed.
 
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