ziptie break bleed

[chappy]

Hi there my zx6r 99 front break looses strenth after few hundred miles .. its 6 pots
I replaced pads and bled them worked fine for week or two then started to loose strengh . Now i find my self re bleeding them every month or so witch again work fine then not .

Iv read that you should zip tie the front break to bars over night to get rid of the air ? With this method do you still crank open the nipple and leave open over night open and do u still leave cap off the fluid . The above method dont state on forums thanks .

[Rogerborg]

I'm not sure what this is intended to achieve. It pressurises the system, but how that forces air bubbles to move in a particular direction escapes me.

Not that I haven't tried it, but I've only really got brakes firmed up by moving fluid through them either one way or another.
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[weasley]

One possibility is that pressurising the system reduces the size of any air bubbles as they compress, giving the chance of greater mobility through small openings (so a possibility of natural migration to the highest point, usually the master cylinder).
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[ms51ves3]

[Polarbear]

Put the bike on the side stand, bars turned so the master cylinder is at its highest point. Pump the brake lever till it goes had and cable tie the lever. Leave overnight.

It has worked for me when I have had real problems bleeding a system but I have a vacuum bleeding system now so haven't used this method for a good while.
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[Pete.]

[Polarbear]

[Pete.]

[Rogerborg]

[Polarbear]

Despite Petes logic and Rogers whining, I am convinced it works.

If you cant bleed, cable tie and leave it overnight, it will work
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[Kickstart]

Hi

My theory of how this works is that it compresses the system, pushing the pistons out a touch, etc, and gives the air bubbles a chance to settle back to the top of the system. Hence when the lever is released the pistons move back, pushing fluid back up the system and pushing the bubble straight out into the reservoir.

All the best

Katy
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[Rogerborg]

Despite what's-his-name's charming faith-based fettling, I'm still not clear on the technomagic that happens compared to doing repeated slow squeeze, hold and release.

Scootch, too cheap to pay for cable ties.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Ariel Badger]

[Raffles]

The simplest and cheapest (free) way of bleeding breaks [sic] that I have found is using one of these contraptions:-

https://i.ytimg.com/vi/hEfEUPGq4WI/maxresdefault.jpg

Like so:-

https://s30.postimg.org/sbxaz43fl/IMG_5792.jpg
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[Pete.]

I tried that once using a proper vacuum pump. Dragged air in past the brake lever pushrod seal.
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132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Raffles]

[Northern Monkey]

[recman]

I'm just glad to see we've stopped calling them zip ties.

[stinkwheel]

In my experience, tying down the lever on a brake which has almost, but not totally bled, does firm things up.

I reckon there are two bits of physics at work here.

1) Pressure. We're talking very high pressures in a hydraulic system. Compressing air bubbles will make them smaller. Conversely, releasing that pressure will make them bigger. Abruptly releasing that pressure will make them bigger quickly.

2) Gravity. Brake fluid is more dense than air. The air will land up at the highest point of the system.

So. We tie the lever down. Pressure makes the bubbles smaller. Gravity ensures they start to rise to the highest point. This takes some time but not necessarily overnight. I reckon an hour will do it.

So after our hour, we have a mass of small, pressurised air bubbles sitting at the highest point of our hydraulic system. ie. just behind the master cylinder seal. We release the lever. The decrease in pressure causes the air bubbles to expand, this will be a pretty abrupt and marked expansion with all the air bubbles already touching one another. In my minds eye, this will cause them to coalece into one, larger air bubble. It's sitting right at the top of the system so it pops up into the master cylinder reservoir.

With the above in mind. I make sure I release the tied down lever in a smooth, steady motion so it goes fully out without "bouncing" then don't touch it for a few seconds.
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[Robby]

Thinking back to the original problem, brakes should not require frequent bleeding. They require bleeding if the system has been drained and needs refilling, but otherwise brakes are generally self-bleeding. Air gets to the top and finds its way out.

If your braking system requires frequent bleeding, then air is getting it. This could be through a bad join (loose banjo bolt, knackered crush washers re-used too many times), a leaking piston seal, a leaking master cylinder, or a holed line.

[chris-red]

I've never had ANY trouble with a tube and a jam jar. It's so quick and easy I don't understand why people try all of these weird and wonderful methods.

Half fill the jar with fluid, attach the tube to the bleed nipple and keep the other end submerged, open the bleed nipple and pump the lever till the bubbles stop coming out. Make sure you don't let the reservoir run dry. then tighten the nipple it is that easy.
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[c_dug]

I once bought a (not very) fancy one way valve on a bit of tube, so you can bleed without faffing with the bleed nipple. that made it a properly simple job to bleed the brakes, unsure if I still have it laying around somewhere but it was well worth the quid or two I paid for it.

But generally in agreement with the above - I've never struggled much with a tube and a jar - and if they are losing pressure there is most likely an issue somewhere.
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