Brake bleed

[shade]

OK all - swapped the OEM lines for braided and Brembo RC19's.
Bled the fronts at both the calipers and master cylinder. Brakes feel nice and tight.
I think there me a little more air so I am going to bleed at the ABS pump.
Question is - Do I crack the front MC or the front lines. The ABS pump has two. Should I do both?

F those stupid oem hardlines @c10

 

[SSGT_B]

Did you bleed at the banjo fitting on the mic? Leave over night with the lever tied down?

 

[shade]

Did you bleed at the banjo fitting on the mic? Leave over night with the lever tied down?

I did! I did not leave the lever tied down and the thought is all the places to bleed the Brembos

 

[sixpack577]

Bleed the calipers, then the master cylinder, then the abs module.
Use Both exit line bolts on the abs module to open/close like bleeder screws(one line for front, one line for rear).
When done and brakes feel good, then ziptie lever to bar, and hang a small weight on the pedal, leave a few hours and bleed again, that will get the remaining air out, as the applied brakes will force all the air to the end of the lines.

 

[wreckwriter]

Tying the lever and the pedal overnight is one of the best tricks.

 

[ottafish]

It’s an interesting topic for conversation..
I’ve read many reports, some by “dynamic fluid engineers” who reckon the zip tie trick is nothing more than the constant pressure causing the tiny air bubbles to break down and get absorbed into the fluid. They argue the minute air bubbles/pockets cannot force their way out as they are under constant pressure.

Then there are reports of the brakes feeling so much better after doing it..

Either way, I haven’t found a totally 100% agreed answer.. yet. I’ve been reading reports on this trick for years..

 

[SS4Luck]

I did the zip tie trick on the front and it was the only way I was able to get all the air out of the line I run from the rh caliper to the left hand caliper.


I don’t have an ABS module to mess with or I don’t think I’d have even tried to change the MC

 

[pcs]

isn’t one of the reasons you have to replace brake fluid is bc it has absorbed too much moisture from air. moisture leads to corrosion and when brake fluid gets too hot the water can come out of solution cause air pockets in the system. also the more oxygen its exposed too the more it will oxidize the fluid. im not arguing it doesn’t make the lever feel better just not agreeing with the explanation.

 

[sixpack577]

It’s an interesting topic for conversation..
I’ve read many reports, some by “dynamic fluid engineers” who reckon the zip tie trick is nothing more than the constant pressure causing the tiny air bubbles to break down and get absorbed into the fluid. They argue the minute air bubbles/pockets cannot force their way out as they are under constant pressure.

Then there are reports of the brakes feeling so much better after doing it..

Either way, I haven’t found a totally 100% agreed answer.. yet. I’ve been reading reports on this trick for years..

All I can say is that I have done this many times, and every time I get more air out.
It's usually a small amount, but sometimes it's more than expected.
It's a closed system, so the air must be(is) already throughout the fluid.
There is a reason that the air moves to the end of the line under pressure(obviously, lol) but I will not try to expain it (incorrectly).
There is no dramatic, if noticeable at all difference in feel unless you had a big air pocket, then it would help.
Where you wouldn't otherwise know that it Was helping would be when the brakes are really working, especially in hot weather, meaning the fluid is really hot...and causes any air in the line to expand, which could cause a fade or spongey feel sooner.
It's always just been a 'why not?' for me personally.

 

[Berlin Germany]

(...) Leave over night with the lever tied down?

sory
but the zip tie trick can´t work at an abs-system - physically imp. , because air bubbles never go down what they would have to do at the abs lining.

the trick is only working at oldies with one or two direct lines from master to the caliper(s) .

 

[SSGT_B]

Good to know. Thanks bubba

 

[sixpack577]

sory
but the zip tie trick can´t work at an abs-system - physically imp. , because air bubbles never go down what they would have to do at the abs lining.

the trick is only working at oldies with one or two direct lines from master to the caliper(s) .

Incorrect.
I have personally done this on a 2018 Gsxr1000R with ABS as well.
I bled the system, and the abs module, and had no more air coming out, at all.
I tied the lever and put a weight on the pedal, just as I've done multiple times on non-abs bikes.
And, the next day, I bled the brakes again, and yes...more air came out.
There IS still air in the lines on Both sides of the abs module.
I used the abs module exit line bolts as bleeders too, no need for an electronic tool to activate the module.
Brakes are still rock solid after a year and a half, and the fluid is still clean, I will replace it this winter.

 

[Berlin Germany]

@sixpack577

ok new (small) doctoral thesis

at least on the hayabusa (gen2 or 3) the abs block is installed almost directly on the transmission block
from there the line goes uphill to the steering head and from there
- on the gen 2 -downhill again to the right brake caliper
- on the gen 3 to a distributor and from there to the left and right individually to both brake calipers.

the zip tie trick can't work here
because the remaining air, which is still hidden in the system, can never overcome the "high point" on the steering head - without movement of the fluid - and can therefore never be released at the brake caliper via a bleeder
it never falls downhill.

THAT is physically impossible.
___________________________________________

little excurs:
in a drinking water pipe it is completely different - the water flow when tapping water pulls the air with it and thus vents the pipe if the diameter matches the amount of water flowing through.

in a heating system, a bleeder must ALWAYS be placed at a high point of a line together with an air collector
- otherwise the air bubble will remain at the high point and the heating can never work behind this high point.

when a radiator gurgles, there is air - usually at the end - in the radiator and it doesn't get really hot in that area, like in the front where the valve is located.
here the radiator is the collecting vessel.
end of
____________________________________

back to the brake
only possibility, e.g. with a cross over routing over the fender , like on the gen2 , you can fool the air by completely dismounting the left brake caliper , holding it up so that its bleeder is high enough to prevent a possible air bubble from the right caliper to the left caliper - almost by itself - can ascend.

the zip tie trick only works with brakes whose hoses only lead upwards from the calipers to the master - only then can the pressure in the system force the bladder to move upwards to the reservoir.

THAT is also the reason why I ! only install two LONG steel braideds (master to saddle LH & RH) and never more a cross over lining - the (my) system vents itself almost constantly and automatically in the direction of the master / reservoir.
spongy brake by bubbles / air in the system should be now history.

greets from a german craftsman in heating ´n plumbing
plus certyfied engineer in piping etc. for heating / chilling systems.
believe me - i KNOW what issues air in pipes can cause.

 

[sixpack577]

I understand the physics.
There is still air between the master cylinders and calipers on abs bikes...and more air still bleeds out from there after leaving the brakes applied.
As said, I have done it.
I am not bleeding the abs module a second time again either, so any minute amount of air left there would remain.

 

[dcnblues]

You will need to use the exit line bolts at the ABS unit as the bleeders, as there is no bleeder there.
Otherwise, you will not get out the air between the master cylinders and the ABS unit.
Put a rag over the wrench when you break each loose and retighten, and that will prevent any mess from brake flluid spraying out.
Also, you need a brake vacuum, as you will never gravity bleed them.
Bleed the calipers, the mc's, then the ABS unit, then back to the mc.
When done, ziptie the brake lever to the bar, and hang a weight from the brake pedal, to keep the brakes applied for several hours, overnight is ideal.
This will cause all the air that is still in there to move to the end of the lines/the bleeders.
Bleed each caliper and MC once more(you Will get a litle more air out) and call it done.
I have put ss lines on and bled them on the Gsxr1k R ABS, and no fancy tools are needed to activate the ABS module if you use it's line bolts as bleeders.
That is an old school trick for front master cylinders that didn't come with bleeders, and it works the same.

-If you are using the ABS exit bolts to bleed the ABS, how do you reconnect the calipers to the ABS without putting air in? I also don't understand the order of the way you do it. How about bleeding the calipers, then the master cylinder to get the big bubbles out, then putting pressure on front and rear overnight, then the master cylinder, the ABS, then reconnect the calipers and bleed them (but you now have air between the calipers and the ABS). I feel like I'm missing something.
-Do I understand it correctly that with a vacuum you don't need to pump the lever? You just leave everything open and continuously fill the reservoir as you vacuum from below?
-What I really don't get is reconnecting a hose to a bolt without having to flush the whole system. Maybe there's some technique where you top off the line before reconnecting, but that seems messy and highly skilled???
-Your way seems thorough but also like you might need to buy two bottles of fluid or a big bulk container.

 

[dcnblues]

Part of me also just wants to buy a big syringe and push the fluid in from the bottom of the system. Bubbles are buoyant and want to go up so you get the flow going in the right direction.

Extraction and fill syringe

I can't imagine an argument against doing it this way. There aren't any check valves preventing the fluid from moving up (unless the ABS would prevent it?), and you could rig a siphon with its own valve to drain the fluid from the reservoir.

 

[shade]

Pushing is fine.
I just used a combination of the ideas posted.
Vacuum bleeder on the caliper first.
Pull down new fluid.
Pushing the lever helps push air out if you have a helper.

After new fluid is coming out I move to the bleed valve on the master cylinder. I had the best luck using zip ties overnight as many mentioned.

Then at the master cylinder bleed valve connect a hose and put it in a bottle of clean brake fluid. Loosen bolt and push air out.

Abs- cracking the bolt with a little lever pressure worked. Once fluid comes out tighten the bolt.

Hope this helps

 

[dcnblues]

the abs block cannot have contaminants get into it and there are contaminants that get into the brake line and they make their way down to the caliper just because the contaminants are heavier and they make their way to the farthest point in the system the lowest point in the system.

Just saw this on a YouTube video. So that makes me nervous about pushing without a conventional Purge first.

 

[dcnblues]

Then at the master cylinder bleed valve connect a hose and put it in a bottle of clean brake fluid. Loosen bolt and push air out.

Abs- cracking the bolt with a little lever pressure worked. Once fluid comes out tighten the bolt.

Not following, sorry.