Bleeding Bloody Bleeding Brakes

[Laava]

The reason they site for dong it, sounds like bulshit to me.

The remaining air in the system is forced out. To where? Through what?
v

As I said in a previous post, I believe it must gravitate to the top, at the master cyl, and then burp out when the lever is released. The fact it worked at all fuckin amazed me! But it did and did not need to be re done. I thought it might go spongy again but no. I am no stranger to rebuilding brake systems on my own stuff, this was a new one on me. Maybe it will only work on a system that is predominantly pointing downhill like a front motorcycle brake?

When bleeding the brakes (front or back) ... if two people do the job ... one works the levers (A child's play ??), the other works the bleed valve .. [you] ... it gets done quite quickly. Regular top-ups of the reservoir ... Done.

Yeah, nah, this did not work for me. I spent a couple of days doing this and in sheer desperation trying the taping the lever thing. Should have done it to start with but like you, refused to believe it could work.
We are not debating the existence of god here people! Just trying to help based on what worked for me.
Good luck gwigs.

[bogan]

There's probably some fandangled explanation to do with bubble size/pressure or viscosity or some shit if taping the lever does help. With the commoners just giving the simple explanation of it 'forcing bubbles to the top'. Would be interesting to know exactly how it is supposed to work though...

[Laava]

Interestingly enough, you have no way of testing this method unless you are in the situation I was and I believe from his description, gwigs has the same symptoms. Waiting to see if he tries it!

[Drew]

Interestingly enough, you have no way of testing this method unless you are in the situation I was and I believe from his description, gwigs has the same symptoms. Waiting to see if he tries it!

You really are struggling with the fact, that if he does it properly, he wont need to do as you suggest.

[Subike]

molecules of oxygen (air) suspended in the brake fluid when not under pressure will just sit.
pressurize the fluid , and the oxygen particles will be forced to move, being that they are lighter than the fluid molecules, they will rise.
When the pressure is released, this gathering of the oxygen molecules will be expelled,
Im not the best at explaining this on paper, just having it explained by a hydraulics engineer when learning many years ago the principles of braking systems etc. as an apprentice mechanic attending tec.

[bogan]

molecules of oxygen (air) suspended in the brake fluid when not under pressure will just sit.
pressurize the fluid , and the oxygen particles will be forced to move, being that they are lighter than the fluid molecules, they will rise.
When the pressure is released, this gathering of the oxygen molecules will be expelled,
Im not the best at explaining this on paper, just having it explained by a hydraulics engineer when learning many years ago the principles of braking systems etc. as an apprentice mechanic attending tec.

Air is lighter than the fluid at all times though, it will always try and rise, hence the trapped air pocket problem. Or do you mean that the fluid absorbs the air when under pressure (so no air bubble)? the absorption being distributed around the fluid, so when pressure is released, so is the absorbed air, but it is released either at the top, or all over the system in minute parts which make their way to the top, thus removing air from the system.

[ducatilover]

Speed bleeders are teh shizz, I'll be buying some (thanks for the reminder)

I generally do it as Drew has said, I also move the brake spliiter around on my Kawasaki as it sometimes gets bubbles sitting in it and the master... and the calipers.
Pricks of things

[AllanB]

I changed to SS lines a couple weeks back. Front end took a lot of pumps to get up to pressure - usual shit just when you are pissed off one more squeeze works!

To their credit HONDA place the bleed nipples at the top of the calipers.

I have had success in the past with removing calipers and securing them higher than the master cylinder.

Hell try the zip-tie brake lever solution - let us know if it works.

[pete376403]

Pray then, why are they strapping the lever back? It would make no difference as to separating the air from the fluid.

I'm not offering do your brakes by the way.

Holding the lever back (ie cable tie to the handlebar) will cause any air in the system to dissolve into the fluid, giving the effect of a good "hard" brake lever.
Apparently exactly the same as scuba divers getting air dissolved into the bloodstream when diving too deep (ie too much external pressure).

When the divers surface (ie the external pressure is released) the air seperates from the blood into bubbles, commonly referred to as the bends. Often fatal.

When this happens with brakes the results can be fatal also.

Unless someone can give a reasoned, technical answer about why something does or doesn't happen with brakes, unexplainable techniques are probably best avoided.

[FJRider]

I don't agree with leaving the top of the master cyclinder cover off though 'cos brake fluid is quite hygroscopic.

It's not that big an issue actually. There will be more risk of/from air in a half full bottle of fluid on your workshop shelf.

Interesting reading here ...

http://soarer.ace.net.au/brake_fluid.html

[Laava]

You really are struggling with the fact, that if he does it properly, he wont need to do as you suggest.

The only thing i didn,t try was reverse bleeding. If the tying the lever back didn,t work I would have had to take it to the motorbike shop. Believe me, I spent a lot of time trying to get this right.
You are struggling with the fact that this works.

Holding the lever back (ie cable tie to the handlebar) will cause any air in the system to dissolve into the fluid, giving the effect of a good "hard" brake lever.
Apparently exactly the same as scuba divers getting air dissolved into the bloodstream when diving too deep (ie too much external pressure).

When the divers surface (ie the external pressure is released) the air seperates from the blood into bubbles, commonly referred to as the bends. Often fatal.

When this happens with brakes the results can be fatal also.

Unless someone can give a reasoned, technical answer about why something does or doesn't happen with brakes, unexplainable techniques are probably best avoided.

I have to admit I was extremely sceptical about this procedure. So would you then expect the air to reappear as bubbles and the brakes would go spongy again? I did, but that didn,t happen. Although I have to admit I was nervous about it and eventually rebled the system with fresh fluid. This time it bled through perfectly.

[pete376403]

Possibly after tying the lever back, the entrapped air was dissolved into the fluid which made it possible to purge when you rebled with fresh fluid. Or something. Good that you got it sorted.

After fitting braided stainless lines on the front of the GS1100, I resorted to stringing the calipers up above the master cylinder, with packers between the pads to keep the pistons in, to get them properly bled and these are just plain ol single pot calipers. I coud imagine modern 4 or 6 pot calipers to be a lot more difficult without some sort of pump system.

[ducatilover]

Possibly after tying the lever back, the entrapped air was dissolved into the fluid which made it possible to purge when you rebled with fresh fluid. Or something. Good that you got it sorted.

After fitting braided stainless lines on the front of the GS1100, I resorted to stringing the calipers up above the master cylinder, with packers between the pads to keep the pistons in, to get them properly bled and these are just plain ol single pot calipers. I coud imagine modern 4 or 6 pot calipers to be a lot more difficult without some sort of pump system.

Fours are fine if you do it right. Sixes can be pretty bloody 'orrible though but sixes are pretty...

[Ocean1]

Fours are fine if you do it right. Sixes can be pretty bloody 'orrible though but sixes are pretty...

Meh. More is always better.

[ducatilover]

Meh. More is always better.

I'll agree there. I've had fun with air locks in a ZRX400's 6 pots, but got there after an hour or so

Might slam a set of gixxer/busa ones on my Krapasfaki