Rear Brake seizing up - Ducati 899 Panigale Forum
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post #1 of 12 Old 08-22-2019, 05:00 PM Thread Starter
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Rear Brake seizing up

I think i have some are in my rear line as the hose from the resevoir to the cylinder failed...
I've bled it at the caliper twice now. I even held the caliper up to allow the bubbles to rise to the top...
but after going on a ride, my caliper was starting to seize up again from the air expanding under the heat...

I completely forgot that the rear brake line goes to the ABS unit and THEN all the way back to the rear caliper... Tthere could be a ton of air in that line...

Has anyone just removed hte ABS and run the lines straight to the calipers like the old days?
or does anyone have any suggestion on how to bleed this line or the ABS unit? is there a bleeder on that?

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post #2 of 12 Old 08-24-2019, 08:47 AM
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Hey Kris -

To bleed the ABS unit you really need a vacuum type blended like the ones that MityVac makes. You can get them at auto parts stores or online.

One of the first mods I made to my bike was to delete the ABS and run lines directly to the calipers from the master cylinders. My bike only sees race duty (and has since new) so you may more may not want the added safety of ABS on the road.

When I did mine there was no ECU hack for deleting the ABS, so the pump and block remain on my bike, but filled with fluid and with brass plugs in all of the ports so it thinks everything is cool. There's probably a more sophisticated way to deal with this now.

Getting all of the air out of the ABS stuff is a PITA, but totally do able, you just need the right tools.


Another thing to consider is that maybe your rear brake pedal is adjusted without enough free play. If this is the case then pressure only builds in the system, it never gets released back to the reservoir. try putting a little slack in that linkage, you'll have to push the pedal a little further to get the brake to engage, but the pressure in that system won't constantly build.

good luck!
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post #3 of 12 Old 08-25-2019, 09:57 AM Thread Starter
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Thank you for the reply Rybo
That's exactly the plan i want to do. Was there any specific kit you were able to find for the brake lines? or did you have them custom made?
Do you know the specs on the banjo size/thread that our bikes use?

I'm thinking i may try something else in the mean time too... Being that that the ABS unit is higher than all of the rear brake components, i'm sure the air is just staying there. So i'm think i may able to crack open the banjo bolt at the ABS unit, push some fluid/air from there and close. Since there are 2 lines, i'm gonna have to figure out a way to force fluid up from the caliper too...
it's just an idea.

as for the linkage slack, i'm pretty sure tha's not the problem. everything is and was fine until the line from reservoir had a tear in it i didn't know about. SO i was basically pumping air from cylinder, right up into the ABS unit. The bike is fine, until it gets hot. THat expanding air is make my brake burn up. It had so much pressure, there was fluid leaking out of the caliper... Once it's cooled, or at the start of any ride, everything is normal.
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post #4 of 12 Old 08-26-2019, 11:34 PM
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Quote:
Originally Posted by krissrock View Post
Thank you for the reply Rybo
That's exactly the plan i want to do. Was there any specific kit you were able to find for the brake lines? or did you have them custom made?
Do you know the specs on the banjo size/thread that our bikes use?
The bike uses standard banjo bolts at all the regular locations.

My bike is one of the first ones in the country, so no kits were available. I had some custom hoses made up at Speigler - looks like they have some kits available for this application now through Ducati Omaha (a site sponsor!). Look here. https://www.ducatiomaha.com/products...abs-delete-kit

Good luck!
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post #5 of 12 Old 08-27-2019, 09:24 PM Thread Starter
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damnit...none for the rear.

So, i did crack open the banjo at the ABS and pump up from the brake, and closed at the same time. Hoping that if there was any air in that line, it was pushed out...I also removed the rear brake and the lines from the side of hte bike so that it was able be raised above the bike almost above my head....
I let the bike get hot, and i bleed it some more...
it's really also impossible to know if it worked without taking it for a ride...so i hoped that worked. In the mean time, i'm gonna see if i can order any custom lines anywhere..

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post #6 of 12 Old 08-27-2019, 09:42 PM Thread Starter
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HEL allows you to create and customize your own lines...

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post #7 of 12 Old 08-28-2019, 11:53 PM
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[...] my caliper was starting to seize up again from the air expanding under the heat...
That makes no sense, technically. The rear brake circuit is completely open (meaning that the caliper is directly connected to the reservoir) until you press on the pedal. In fact, you can push the caliper pistons in, and the fluid would freely move back into the reservoir. And unless the reservoir is completely full and the fluid has no place to go, it's impossible for the circuit to build up pressure.

Like Rybo said, make sure there is enough play at the pedal: as you press down on it, you should feel the resistance of the spring right away (no free play) and then feel the added resistance caused by the master cylinder piston. You might move the pedal only a couple millimeters to feel this extra resistance, but if you don't, chances are that the master cylinder piston is partially obstructing the reservoir hole when cold, and totally closing it (causing the system to build up pressure) when hot.

I'm not saying this is the cause of your issue, maybe it's something related to the ABS, but the fact that your brake is seizing up means that the circuit is building up pressure.

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post #8 of 12 Old 08-29-2019, 12:15 AM
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[...] It had so much pressure, there was fluid leaking out of the caliper... Once it's cooled, or at the start of any ride, everything is normal.
This also seems to confirm that the fluid is not free to expand back into the reservoir, as that would be the very first place where it would leak from.

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post #9 of 12 Old 09-02-2019, 12:57 PM Thread Starter
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That makes no sense, technically. The rear brake circuit is completely open (meaning that the caliper is directly connected to the reservoir) until you press on the pedal. In fact, you can push the caliper pistons in, and the fluid would freely move back into the reservoir. And unless the reservoir is completely full and the fluid has no place to go, it's impossible for the circuit to build up pressure.
you gotta go take look at your bike... The banjo off the rear brake master cylinder bends to the right, away from the rear caliper.... Because it's going to the ABS unit in the front of the bike...
When you pump the rear brake, the fluid is passing through the ABS unit first.

And yes, technically, the fluid should simply start to go back into the reservior...but i can't explain why that wasn't happening.
All i can say is that i had a cut in the line, obviously air was getting into the system. And we all know air expands when hot...brake fluid does not. So i kept bleeding and bleeding it..but when it comes to the rear brake, the ABS unit is physically HIGHER than the MC and caliper... SO any air that gets in there is gonna wanna stay. Plus it's attached right to the engine (hottest part of the bike) so any air in there is gonna expand like crazy. I don't know how ABS unit work...it's possible that the air was on the back side of a piston that was then now allowing the fluid to pass backwards into the reservior...?

2014 Panigale 899 - Red
Front and Rear R&G Sliders , Rizoma B-Pro pegs, Ducati performance carbon tank protector, Pit Bull Spools, NRC FEK, R&G Radiator Guards, Zero Gravity Corsa Windscreen, Red Wheels, ProGrip 717, Heated Grips

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post #10 of 12 Old 09-02-2019, 06:26 PM
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Originally Posted by krissrock View Post
you gotta go take look at your bike... The banjo off the rear brake master cylinder bends to the right, away from the rear caliper.... Because it's going to the ABS unit in the front of the bike...
When you pump the rear brake, the fluid is passing through the ABS unit first.

And yes, technically, the fluid should simply start to go back into the reservior...but i can't explain why that wasn't happening.
All i can say is that i had a cut in the line, obviously air was getting into the system. And we all know air expands when hot...brake fluid does not. So i kept bleeding and bleeding it..but when it comes to the rear brake, the ABS unit is physically HIGHER than the MC and caliper... SO any air that gets in there is gonna wanna stay. Plus it's attached right to the engine (hottest part of the bike) so any air in there is gonna expand like crazy. I don't know how ABS unit work...it's possible that the air was on the back side of a piston that was then now allowing the fluid to pass backwards into the reservior...?
I don't question that you have air in the system, and I don't question that the air might expand when the ABS unit gets hot. I'm saying that this extra pressure should be visible at the reservoir (which is not designed to withstand high PSIs and would leak very easily) before seizing a brake. The only explanation I have for the behavior you're describing, is for the master cylinder piston to obstruct the reservoir line, hence closing the system and allowing it to build pressure. When your bike gets hot and the brake starts to seize, would opening the reservoir release the pressure (careful, put a rag around it before you try and open slowly, as fluid might come out) and free the brake?

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