Stainless brake line questions

[psycoreefer]

Hey guys, I have no doubt that these questions are in the archives somewhere, but I've given up trying to find them, maybe someone can point me to the threads or can answer off the top of their head.

I want to build some stainless lines for my brakes, I want to convert from the 3 line system in the front to a 2 line, 1 from the master to right caliper and 1 from right caliper to left caliper. I plan to order my parts from an plumbing.com. My questions:
1. Does anyone know if a straight banjo will work on the front calipers instead of a bent(15 degrees?) one?
2. Does anyone know the length of the rear line and types of fittings needed for a 79 special?
3. Has anyone done what I propose to do and if so do you remember the final lengths of your lines?

[DGXSER]

Hope these help....

1. Does anyone know if a straight banjo will work on the front calipers instead of a bent(15 degrees?) one?

Define work.... You could bolt it up, but getting to the bleed screw ill be a PITA and I woudl think the line will rub on the caliper so I would not recommend it.

2. Does anyone know the length of the rear line and types of fittings needed for a 79 special?

Assuming it is the same as an SH, it will be 49cm, cl to cl of the holes. 15 deg offset at both ends.

3. Has anyone done what I propose to do and if so do you remember the final lengths of your lines?

I am betting no, because you will get uneven pressure to the two calipers this way. The accepted norm is to run two lines from the MC to each caliper, eliminating the splitter. This way you keep equal pressure to each caliper and even braking.

[randy]

Never done exactly what you're doing, but the stock line lengths for a Special are:

M/C to Union: 20-1/2”
Union to caliper: 22-3/4”
Union to caliper: 22-3/4”
Rear M/C to caliper: 19”

All banjos are 10mm (or) 3/8"

[fredintoon]

- - - I want to build some stainless lines for my brakes, I want to convert from the 3 line system in the front to a 2 line, 1 from the master to right caliper and 1 from right caliper to left caliper. I plan to order my parts from an plumbing.com. - - -

Hi psyco,
OK, others have posted the numbers.
BUT
Road vehicle brake hoses need to made by a DOT approved manufacturer. Is your plumbing shop DOT qualified?
As all know, insurers are crooks and will seek any excuse not to pay out, as:- "His lines were not DOT approved."
Never mind that you were stopped at a red light and got rear ended by a texting soccer mom.
And anyway, that loop of line from one caliper to the other will look kinda stupid.
What'd look really trick is to gun-drill through the front axle mebbe 1/8"diameter, braze up the cotter pin cross-holes & use a Nylok axle nut, then tap each end of the axle for banjo bolts to run the hydraulics through the axle.
You gotta bleed the brakes each time you take the wheel out but nothing's perfect, eh?

[79XS11F]

B Safe, Buy them from a SS brake line supplier, install them, bleed them and walk away knowing you have done the right thing.
Rob

[psycoreefer]

Hope these help....

I am betting no, because you will get uneven pressure to the two calipers this way. The accepted norm is to run two lines from the MC to each caliper, eliminating the splitter. This way you keep equal pressure to each caliper and even braking.

Wondering about this assertion, how is having one line from MC to caliper and 2nd line from caliper to caliper different then having one line from each caliper to the MC.
I thought that the pressure in the system was the same regardless of how the system is connected.
Good to know straight fittings won't work, I agree that the bleed screw needs to be accessible and that rubbing is bad.

fredintoon:
I could (and may) have the lines made up by a certified shop, all the same questions still apply - I have to know how long the lines need to be and what kind of ends to have put on them, and then order the lines. I agree through the axle would look "trick" but beyond my abilities and resources to do. As for the loop from caliper to caliper I'm thinking that you won't notice it as I'm planning to "hide" it behind the fork brace so the entire loop would follow fork tube up, brace across and tube down.

Does anyone know if you can stack a pair of "bent" fittings with a double banjo bolt without them rubbing each other?

[DGXSER]

Wondering about this assertion, how is having one line from MC to caliper and 2nd line from caliper to caliper different then having one line from each caliper to the MC.
I thought that the pressure in the system was the same regardless of how the system is connected.

Your MC applies even pressure, the length of the line causes friction against the fluid moving through it and therefore, less pressure is at the end of that line than at the top. So, then the line going from one caliper across to the other will lose more pressure. Assuming you wil be running up one fork across the fender and down the other fender, you could have up to twice that line loss to the other fender.

To put into numbers (totally fictional just to depict the issue) if you have 20 psi at the MC, and you have 3' of line to the first caliper and you lose 1 psi per foot (Much greater than truly possible or likely anyway) you now have 17 psi when you get to the first caliper. If you run equal length lines in parallel to each caliper then each caliper would have 17 psi. The way you plan to run it, if it was another 3' of line to get across to the other caliper, the second caliper now has 14 psi. Pressure does develop equally, but the MC puts out equal pressure and line loss will effect the end pressure at each device. Hope that helps.

[psycoreefer]

I'm in agreement that that would be the case if we were trying to flow a volume of fluid and measuring the pressure of the fluid at some given flow rate. For instance if we were talking about air lines and trying to run some pnumatic tool that required 50psi at 30cfm or something.

The part I think throws this off is the fact that applying the brakes moves a very tiny amount of fluid and counts on the fact that brake fluid doesn't compress to make the brakes work.

If what your saying is true (and I realize that you probably just pulled numbers out of thin air as an example) then my car would always stop crooked because the lines (all of them ) going to the passenger side are longer then the ones going to the drivers side because the master cylinder is on the drivers side. The difference in length there is much more then it would be between my two calipers.

[motoman]

Huh?.........sounds good but doesn't work that way. Bottom line of a complicated explanation is same volume of fluid is flowing under a given amount of pressure and no blockages is gonna be the same with or witout a direction change. Volume is already there in the line, It is just having a pressure source added.....

[TomRodgers]

proportioning valves take care of that in automobiles. The lines, no matter where they are, or what length, being full of fluid, when the brakes are applied, the valve sets equal pressure to all 4 lines.... having BOTH lines 'split' at the caliper would look a little odd i would think....JMO. If you are trying to run them 'in line' with each other, there WILL be a slight drop in volume pressure to the furthest piston. I doubt it would be enuf to notice, but you may wear out the 'first' set of pads quicker....then again, i may be wrong.... If unsightly lines are your issue, then you could always get the front lines (2) of them a bit longer, and secure them to the forks (as long as the 'clip' allowed vertical movement to allow compression/expansion of the fork tube) and that would clean up the front.......

[CatatonicBug]

If you "daisy-chain" the brake lines, the second caliper won't be actuated until the pressure on the first one is maxed out. Fluid flows to the least-resistant path, so you'll end up loosing a tiny bit of the second caliper's effectiveness.

One thing you might try is to mount a splitter on the back of the fork brace, and have equal lengths of line running to each caliper. JAT.

[crazy steve]

One point that everybody's missing is if you move any of this down onto the lower forks, you're increasing the unsprung weight. That's probably the main reason why these are plumbed the way they are. More weight = less responsive suspension...

'78E original owner

[CatatonicBug]

I can't imagine that the extra few ounces would make any difference in the handling. People add fork braces all the time with no ill effects.

[bikerphil]

As for running a brake line over the fender to the other caliper, my bud's 955 Tiger has a plastic brake line (factory) doing that. Seems to work fine.

[crazy steve]

I can't imagine that the extra few ounces would make any difference in the handling. People add fork braces all the time with no ill effects.

Probably not a large difference, but these things don't handle that great to start with, so why make it worse? As to the fork brace, that improves handling so it's a worthwhile trade-off.

Actually, I'll be a real heretic here and say if the extra line dropping down offends you, why not just ditch one side of the dual disc setup? Rotor, caliper, line. Braking performance in normal street use wouldn't suffer that much if at all, and a swap to a better multi-piston caliper with larger pads would easily restore braking performance. Less unsprung weight, so a better ride and handling to boot.

Flame suit on...

'78E original owner