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Someone once said I aint the sharpest hammer in the tool box. Maybe that's true, I ain't figgered it out yet, Another thing I haven't figured out yet is the air in the brake line thing, I don't doubt it works, there seems to be plenty of evidence saying it does, but Like wimmins, I just don't understand how, and in fact it seems backerds to me. I would appreciate it if someone with less refreshing beverages under their belt and more schoolin could explain where my thinkin went wrong.
Firstly I'm thinkin, brake reservoir is the highest point in the brake fluid system.
Nextly I am thinkin brake cylinders/ pistons are the lowest point in the brake fluid system.
Thenly the whole Newton in the bathtub thing when he farted an said "I found it" ( nasty man).
Also-ly, bubbles rise in fluid cause they weigh less/ are less dense per area than the fluid surrounding them.
Brake fluid is designed not to compress, deal well with heat, an do a job on car paint that ajax ain't gonna fix.

Air aint designed not to compress.
Bear with me for a tiny lie now, water also aint designed not to compress, sorta,.Water in it's gaseous or solid state WILL change it's area per given quantity in liquid state and maybe heated water not at the vapor or stea,, Ok rabbit hole but water in brake lines can change with heat, also can change from water to gunk.
Anyway we aint' really talkin water here unless it has converted and remains in a gaseous or Ice state , I.e. it's fat water, biggern liquid. ( I dunno if water dissolves in brake fluid, is heavier or lighter than brake fluid or neutral , don't confuse me with facts).
So air and water are the 2 contaminants I think of most in a brake fluid system.
So here's my dementia, "air in brake lines can be bled out better by squeezin the brake lever an leavin them squoze overnight".
Air squoze has a smaller area, smaller area is less bouyancy/ higher density. and,,,,should rise more slowly, not more fastly, outta the system into the reservoir.
So I'm thinkin, maybe it can get in to the reservoir better cause the pathway into the reservoir isn't blocked by the squeezer mechanism? Nope if that was true, no squeezin would happen. Maybe the grabontosomethingness of air is reduced when it occupies less space bein squoze. That kinda makes sense, but the riseuppedness has been reduced so the motive force/ adhesion equation should be equal with surface area at least, or in favor of cohesion as molecules are in closer proximity to bond to other surfa,,, i needa beer an some help!
 

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playing along,
When most people think about this they assume the brakes have just fluid and air and that the two are always separate things.

1st bit:
There is also metal, polymers and geometry. A constant high pressure can allow components to creep, snug up and /or take up new shapes. This will take slack out of the system giving a firmer feel which some riders would read as “it bled bubbles out”. This can be permanent or transient or somewhere between.

2nd bit:
If you compress gas and liquid together the gas molecules will tend to diffuse into the liquid. This is how they hide the bubbles in your refreshing beverage until you take the top off. It can take a while for gas to fully separate out again, so feels firmer and “I did me some good bleedin”, or not.

So there is other stuff going on.

kind of related anecdote:
Gas is pretty good at this disappearing trick and will even do it with metal that most regard as impermeable solid.
When I was a sprog a garage owner asked me where he’d gone wrong. He wanted to turn an acetylene tank into a compressor tank. He flushed it with water to purge any gas and took a torch to it. His homemade torpedo exited through the back wall. Thinking that must be last of the gas he carried on and got another smaller pop. Eh?
Years of gas diffused in the metal cell structure making its bid for freedom.
 

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View attachment 100067
What an absolutely brilliant recital.
Thankyou.

(Hope help arrives soon though, sounds like you are desperate for some).
Never fear….. DP is here

Pressure, pushing down on me
Pressing down on you. No man ask for
Under pressure, that takes a nation down
Splits a family in two, puts people on streets

Um ba ba be
De day da

It's the terror of knowing what this world is about
Watching some good friends scream
"Let me out!"

(cut to shrimp under glacier)

Did you hear that?
They're doing it again
Doing what?
This!
What is it?
I have no idea!
What's it for?
Perhaps, it's a momentary relief
from the existencial terrors of existence

It brings out their happy!

(Edited for readability and the reduction of time spent reading)
From the movie Happy Feet 2
based on the song :

 

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When I was a sprog a garage owner asked me where he’d gone wrong. He wanted to turn an acetylene tank into a compressor tank. He flushed it with water to purge any gas and took a torch to it. His homemade torpedo exited through the back wall. Thinking that must be last of the gas he carried on and got another smaller pop. Eh?
:oops: was he tryin' to earn a darwin award?
 

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Discussion Starter · #9 ·
Ail is right! I don eat brown lettuce or green appleso_O
 
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...................................................................................................................

kind of related anecdote:
Gas is pretty good at this disappearing trick and will even do it with metal that most regard as impermeable solid.
When I was a sprog a garage owner asked me where he’d gone wrong. He wanted to turn an acetylene tank into a compressor tank. He flushed it with water to purge any gas and took a torch to it. His homemade torpedo exited through the back wall. Thinking that must be last of the gas he carried on and got another smaller pop. Eh?
Years of gas diffused in the metal cell structure making its bid for freedom.
This is where Welding stuff from Uni is stuck in my head.

An acetylene tank is filled with a permeable clay. The acetylene must be slowly added so it can permeate into the clay. The clay keeps it stable so it does not sloush. If you do not have the clay and try to compress Acetylene to a liquid state, it will explode.
You also never want to lay an Acetylene on its side for transport. The liquid will settle in the clay layers and if you stand it upright some liquid will try to go out the valve. You must stand it upright for 24 hours before use for the liquid to settle back into the bottom and the "Tiny Bubbles" can permeate back up..

In England, before Natural Gas they used Acetylene for house lights and cook stoves. If the "Gas Company" was not careful they got liquid Acetylene in the pipes and a house went BOOM.

Edited for House use
 

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The small diameter of the brake line keeps an air bubble from passing another air bubble. This makes it harder to 'CREAP' up the line real fast.
So when bleeding the brake system you start at the longest run on that line and push the air bubbles out the bleeder.

Any smaller bubbles will climb up to the higest point, like the master cylinder. So when you wire tie or bunge the lever down over night the bubbles can back flow thru the open valve
 

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The old " zip tie brake lever trick" has been around for a while, with volumes of yay/nay discussions, does it work :unsure:
IME, yes. Does it work for everyone or in every motorcycle, no. o_O if there's underlying issues, like bad master cylinder seals, stuck pistons or bad/stiff seals, etc. or just too much air still in system, it won't work. IME you must be able to hold some kind of pressure at master, as in lever not fully contacting grip.

The way I understand it works, is that pressure forces air to highest point at master cylinder, when you release the lever "slowly", the air rises into reservoir thru bleed port, do not apply brake immediately, give it 5 minutes. While the lever is tied, you can try tapping calipers, etc., with a rubber mallet helps release trapped bubbles, I had used a palm sander (without sandpaper :whistle:) on some stubborn "Tokico" 6 pot calipers, etc. If you feel and improvement, but not happy repeat as required.

These modified diagrams kind of explain ...

Arm Product Human body Elbow Font
Product Font Elbow Parallel Rectangle
 
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That is how I’ve heard it explained over the years - but pressure isn’t directional.

There is also the hybrid idea that bubble size is reduced by pressure as Dave says causing them to relocate and then they sit waiting for the piston to release them as in ZRX image.

Or that the volume of fluid downstream increases due getting past the reduced bubble and releasing the lever relocates the bubble a little further upstream out of the pocket trap.

Jiggling the pipes - fair enough.

All things that happen on a ride anyway:unsure:

————————————-
There was a chap called Trouton who did lots of experiments with bubbles in tubes. How they stop/go and speed up/down, straight/spiral etc. according to viscosity.
He made an interesting find on bubble size/length + viscosity and how it changed the forward face of the bubble from flat to pointy speeding it up or slowing it down - a bit like crack propagation.

The weird thing is that it doesn’t follow a constant pattern. As size increases the bubble travel increases, decreases, increases, dec...


edit: interrupted part way through typing
 

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Discussion Starter · #15 ·
sure don't need no more crack propagation around here! The meth and heroin dealers are already complaining about losing market share
 
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Can the pressure cause multiple tiny bubbles to come together to form a larger, more buoyant bubble?
 

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Can the pressure cause multiple tiny bubbles to come together to form a larger, more buoyant bubble?
Generally they tend to do the opposite and shrink away from each other (and new molecules stop precipitating in).
But maybe some might manage to relocate if shrinking/expanding broke some bond holding them on a surface - and then collide as pressure drops and they expand and coalesce that way?.
Bumping along a road would seem better for this than being static over a long period.
 

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