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Old 11-11-2013, 09:39 AM   #16
Boon Booni
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I agree with Motobene, I don't think it has anything to do with getting air out of the system. When the lever is pulled, the vent to the master cylinder is covered up and there is no longer any place for the air to go.

I have tried it, and had it completely fail to firm up the lever on a poorly bled bike with ABS. But I have also tried it had it make a firmer lever. My reasoning is that it stretches the cups/seals in the master cylinder so that on the next pump there is less flex in the system. Similar to how braided brake lines affect feel over OEM rubber lines.
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Old 11-11-2013, 09:42 AM   #17
jonnyc21
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I think the root of his post isn't that it dosnt work, it's a question as to why. What's going on and dose anyone have even an educated guess as to why?

I will not clame to know, however I have done some things like this even when they didn't make sense because it was worth a try and thy worked.

I like Boon's thoughts... I myself would like to hear any others guesses as to why it works... Always infested in better understanding things.
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Old 11-11-2013, 10:01 AM   #18
Sting32
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Another reason the pressure overnight might work is, the "air" is trapped yet settled to the top near master cylinder, So, when you released it, the air exchanged with fluid. I think it is possible in the "closed system" as there is the "inevitable" a small air gab between fluid level in master cylinder and the rubber gasket that covers that fluid with the cap?
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Old 11-11-2013, 05:49 PM   #19
laser17
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Here's my take of whats going on.

Seals in our hydraulic systems are designed to prevent brake fluid / mineral oil from escaping - not relatively tiny and shape shifting O2 molecules. In fact, O2 molecules will permeate the Viton and Nitrile O-rings themselves OVER TIME. (at a pretty slow rate depending on several factors such as pressure differentials) but there tricky little bastards when trying to contain them. (Why N2 is used in shocks for instance)

IMO - The significant source of the any of our leaks will be at the seal interfaces to the ID bores of master and slave cylinders and OD of the pistons. The cylinders are typically drilled, bored and honed, into cast metal and in microscopic terms, they are very rough and fairly porous. Relatively speaking, easy for a small O2 and shapeshifting O2 molecule to pass by. Not easy for the very big, long, brake fluid molecules to pass by. Also - the surface tension (not a small factor here) in these fluids wants to keep all the fluid molecules together and helps prevent individual molecules from slipping by the rough interface. This is Not the case with O2.

As you might guess - what most likely happens is the O2 leaks past the seal to cylinder interface and eventually finds it way into the top of the master reservoir given its the high point of the system. Remember, The slave side of the fluid is under pressure - the master reservoir side isnt. Once the O2 molecule gets past the interface, it wouldn't want to stay there either- it would most likely float up on its own - to the high point of the system. The master reservoir.

One way to test this would be to pressurize the system with air and measure the leak down. I'll leave that as an exercise for you!

One thing that MB said hit me, if this helps turn big air bubbles into lots of very small ones (diffusing into the oil) then the mobility of air across the rough seal interface would be improved.

Keep in mind, in sitting here drinking beer watching football, so all of this may be an atmospheric extraction of a different kind...
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Old 11-11-2013, 07:57 PM   #20
lineaway
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I can just see Laser starting out the game with six different containers. During each mini break he mixes (guzzles) from said container to introduce more co2. Laser says it was a success , but can`t remember how many refills it took to come to this fine conclusion.
I agree whole heartedly with this type of Monday night research!
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Old 11-12-2013, 06:49 AM   #21
motobene
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Quote:
Originally Posted by laser17 View Post
I guess we have a different view on things - which is great.

Please read the above with a smile on your face - im just pushing back cause I think you may be wrong, but know that its really all good.
Being wrong doesn't bother me because being wrong is how we iterate getting it right.

Unwillingness to be wrong is the major human boneheadedness. Tesla invented, patented, and demonstrated wireless communication, radio, but he got obsessed at being wrong about transmitting high amperage power through the air. He was so obsessed he didn't do his calculations. J.P. Morgan, who financed his huge transmission tower in New York that sent wireless signals throughout the universe was misled by Tesla, who was working instead on his obsession. J.P. got pissed, pulled his money, and backed Marconi. Tesla died a pauper.

Still not sure what exactly I'm wrong about on this one, but I am smiling! Honest!

Vacuum engineering can suck. When I did silicone molds or when designing and prototyping computer-controlled hydraulic feet, I'd de gas the fluids, the silicone and the hydraulic oil, in a vacuum chamber. It astounded me how the materials would froth up and for how long. Regarding the silicone, the stuff would froth and froth and froth. Finally, I'd get bored and shut off the vacuum with, "Enough already!" But I found all that show didn't do much, practically, because my molds and feet weren't operating 'in a vacuum.'

But why are we talking vacuum?

There is no vacuum going on in hydraulic brake systems, just pressure, from atmospheric when the system is open to the reservoir, then more pressure when the lever is pulled in. What gasses are in solution won't mysteriously come out, and if a tiny bit that is out goes back in under pressure, it'll come right back out when you release the lever. It's only escape is back through the reservoir port.

Still wondering how the mystery stuff leaks out when the lever is zip tied.
And still smiling!

It's all good
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Old 11-12-2013, 06:54 AM   #22
motobene
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Quote:
Originally Posted by lineaway View Post
I can just see Laser starting out the game with six different containers. During each mini break he mixes (guzzles) from said container to introduce more co2. Laser says it was a success , but can`t remember how many refills it took to come to this fine conclusion.
I agree whole heartedly with this type of Monday night research!
I too like to de gas with a belch or two Just don't want my jaw zip tied shut over night! Might make me fart in bed more, which is bad for marital bliss
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Old 11-12-2013, 06:55 AM   #23
laser17
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I guess you didnt read the post above where I explained what I thought was happening. In the meantime, I ran another experiment that had to be repeated again and again.
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Old 11-12-2013, 06:56 AM   #24
laser17
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Quote:
Originally Posted by lineaway View Post
I can just see Laser starting out the game with six different containers. During each mini break he mixes (guzzles) from said container to introduce more co2. Laser says it was a success , but can`t remember how many refills it took to come to this fine conclusion.
I agree whole heartedly with this type of Monday night research!
+1
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Old 11-12-2013, 07:38 AM   #25
motobene
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Quote:
Originally Posted by laser17 View Post
I guess you didnt read the post above where I explained what I thought was happening. In the meantime, I ran another experiment that had to be repeated again and again.
That's possible. I thought I did, but I'll go back and check to be sure. Gotta go now though, so I'll have to do it tomorrow or later.
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Old 11-12-2013, 09:16 AM   #26
Rockcat
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StuInFh - did your brake make it through your event?
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Old 11-12-2013, 12:00 PM   #27
StuInFH OP
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StuInFh - did your brake make it through your event?
Finally, someone cares about me. ;-)

(Thanks all, but I'll keep bleeding from the bottom, as it has worked for me for over 40 years now on many different vehicles, which is how I define reproducibility of an experiment.) :-) Not news to me of course, but good info re seasoning and cleaning etc. for those that may benefit. thanks

To the point: Success!

Halfway through the 2nd loop the lever completely firmed up and had to be backed off about half of the compensating adjustment I had made. I mentioned this to an old-timer and he said bubbles travel up the line during the night. I said they obviously travel during daylight hours too. ;-)

Then during the 3rd loop the lever lost even more travel and the brake was almost dragging, costing me a point here and there as I over-braked from just looking at the lever. (to be fair, those points were offset when it got so tight by section 8 that when I almost went over the bars while braking too hard on the backside of a log before running over the tape that I quit using it. I took fingers off the brake AND the clutch and just barely made the downhill 180 turn without running over tape, and went full on whiskey throttle! Nearly parted from the bike but managed to hang on as the momentum carried me over the two bike-length spaced uphill logs and up the hill and out the gate for a clean where I had fived earlier!)

Enough about my luck, back to science.

My theory, air bubbles dislodged during riding, which supports my observation that my brake is back to normal. :-) The debris is likely from inner lining of cable (like the old-timer said), due to its composition not matching any other parts in system AFAIK. I'll find out when I cut it open, AFTER it fails for good. ;-)

But I still wonder something from back in my days during seasoning of new pads and rotors on my Vettes and Porsches (lots more fun to heat up those rotors than a TB's, BTW); do brake rotors really warp, or is that a myth? (google it) cheers and thanks to all

StuInFH screwed with this post 11-12-2013 at 12:32 PM
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Old 11-12-2013, 02:57 PM   #28
jonnyc21
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Glad to here it started working for you. I would guess if the bits are the inside of the line, that could have caused the bubbles to ketch near the failure point causing the need for the ride to help the bubbles come out?

Just a guess. And I hope you don't have any moe issues with it.
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Old 11-12-2013, 08:01 PM   #29
Rockcat
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Quote:
Originally Posted by StuInFH View Post

My theory, air bubbles dislodged during riding, which supports my observation that my brake is back to normal. :-) The debris is likely from inner lining of cable (like the old-timer said), due to its composition not matching any other parts in system AFAIK. I'll find out when I cut it open, AFTER it fails for good. ;-)
Waiting can be painful! You know you need a new brake line...
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Old 11-13-2013, 02:10 PM   #30
baloneyskin daddy
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Originally Posted by Rockcat View Post
Waiting can be painful! You know you need a new brake line...
Especially if you grab a handful of brake and it doesn't release. Just replace the line and be safe.
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