Ducati.org forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter #1
Hi guys!

There’s another issue with my monster(( For some reason rear brakes not working. I went to service and had it bleed few times, but after 1 week all the same. The brakes gradually disappears.
I’ve already changed master cylinder (62540201A). Nothing changed though.

To make it clear the caliper was positioned upwards during bleed and brakes were working fine right after the service.

I’ve been in 4 different services nobody knows the reason. Even official Ducati dealers says they have no idea what is the cause of problem. Everyone says it’s normal for Ducati. I would agree with it and don’t care much if they work for at least a couple of months. But brakes disappeared 1 week after bleeding.


Отправлено с моего iPhone используя Tapatalk
 

·
Registered
Joined
·
443 Posts
There is something definitely afoot with the rear brake... failing within a week seems more like air in the abs unit...the current theory for a fix going around now is a brake line( design issue )...but if air can enter you would expect fluid to leak out as well and I have never witnessed that...I'm pretty certain all the air is out of my lines...I can bleed it without removing the caliper in a pinch but still remove it to be sure....still...it will turn soft even with no use over the course of a month or 2...I was attributing it to moisture in the fluid but I'm growing skeptical...anyone claiming a fix really needs to be verified over time...in the meantime...get the pedal tight...ride the abs...repeat.
 

·
Registered
Joined
·
35 Posts
Discussion Starter #3
There is something definitely afoot with the rear brake... failing within a week seems more like air in the abs unit...the current theory for a fix going around now is a brake line( design issue )...but if air can enter you would expect fluid to leak out as well and I have never witnessed that...I'm pretty certain all the air is out of my lines...I can bleed it without removing the caliper in a pinch but still remove it to be sure....still...it will turn soft even with no use over the course of a month or 2...I was attributing it to moisture in the fluid but I'm growing skeptical...anyone claiming a fix really needs to be verified over time...in the meantime...get the pedal tight...ride the abs...repeat.

Some guys from service told me the same, that air might be in abs unit. But others say that abs unit automatically push the air out.

What you mean by “ride the abs”?


Отправлено с моего iPhone используя Tapatalk
 

·
Registered
Joined
·
443 Posts
There's a little chamber in the abs unit sperate from the regular brake circuit where a motor builds pressure as needed...the air in there gradually gets released into the lines but only when the abs unit is in use...so put the abs on #3...hit the rear brake...engage the abs...pedal gets spongy...bleed and repeat until engaging the abs does not make the pedal spongy
 

·
Registered
Joined
·
443 Posts
That theory may be a possibility...but not in my experience...my line by the crankcase is insulated and thanks to the pandemic it sat parked unused and the pedal was sponge worthy with no use...my interval has been 1 to 2 months...and that is now independent of use
 

·
Registered
Joined
·
6,179 Posts
Now I can’t back this up but was sitting thinking about it. And my non abs bike does this. I just ride it and about 10 -15 mins the rear brake is back up. I keep using it even though it’s not working.

now, the design and location of the cylinder is the culprit. The air enters the master at the reservoir feed seal. As you ride it it bleeds and bubbles it’s way back up to the reservoir. I bet that if you could, and you can’t, block off the hose to the caliper you could prove it’s in the master.
Because it goes spongey just sitting Int the garage it is drawing in air, the outlet is at the bottom so the air sits at the top of the cylinder. When you ride and work it the air is displaced.

try this.. remove the feed pipe from the reservoir.. remove the rubber seal and plastic tube, coat these two in red rubber grease and reassemble. Do it liberally and I bet it fixes it. I’d do it but that won’t be for a few weeks.
 

·
Registered
Joined
·
443 Posts
I've tried jumping on the brake pedal to build pressure and work any air that might have found its way in the master...if you ever bleed the brakes and the reservoir went empty that lil air bubble is a tenacious thing to try and coerce back up the tube...but you can see it...jumping on the brake lever typically will get it out...I've never seen any air inside the master outside of drawing it in myself while bleeding... nor has it improved by pumping it...and generally the pedal nearly instantly tightens up after the initial bleed which puts my focus further downstream... however, next time I bleed it I'll put a camera on the reservoir...it would be comical to watch an air bubble rise out of the master while so much attention is on the bleed screw
 

·
Registered
Joined
·
6,179 Posts
Jumping on the pedal will do nothing while there is no pressure. It will just stress the internal seals.
Like I said I check mine as I leave the house and swear it’s bypassing. Ride about 10 mins using the rear as I normally would and it comes back up.. oh and 12 years in automotive brake industry.. and cars don’t do this..
 

·
Registered
Joined
·
18 Posts
Just talked to my dealer. There is a rear brake recall on the 2018+ 821. Mine is a '17 unfortunately. I'm pretty pissed off since I'm having the exact same issue. Ducati needs to get their sh#t together. This seems like a widely-known issue. Guess I'll be paying for the repairs(n):(
 

·
Registered
Joined
·
35 Posts
Discussion Starter #12

·
Registered
Joined
·
35 Posts
Discussion Starter #13
Just talked to my dealer. There is a rear brake recall on the 2018+ 821. Mine is a '17 unfortunately. I'm pretty pissed off since I'm having the exact same issue. Ducati needs to get their sh#t together. This seems like a widely-known issue. Guess I'll be paying for the repairs(n):(
If they point the faulty part it will do too.

Russian dealers insist they’ve contacted the Ducati factory, but they never gave any solution. Only basic reply’s like keep bleeding them.
 

·
Registered
Joined
·
443 Posts
Brake systems are separate from each other...One does not affect the other in a mechanical sense...they each have separate fuids...they are linked in abs setting #3 and #2 electronically...get the rear brake bled properly and carry a handful of front brake deep into a corner...the rear starts walking around you...it's pretty neat
 

·
Registered
Joined
·
35 Posts
Discussion Starter #15
I’ve asked the same question in other Ducati forum. There is a guy with nickname SylSal
who’s got his front and rear lines replaced during recall which eventually solved the issue. I’ve copy paste link to the original post just in case someone needed .

Rear brakes issue
 

·
Registered
Joined
·
443 Posts
Thanks for the update....it's too soon to say that's it....10 years ago it was routing to close to the exgaust...then it was the master cylinder.

...fun fact, the monster 821 shares the same brake assembly as the multistrada and m1200....all with their own issues...all with different assumptions...none have really worked...to be fair...brake lines are the only thing left....was going to just replace them all...but turns out there is no m821 master cylinder to abs replacement from the factory for the 2015 model
 

·
Registered
Joined
·
4 Posts
There's a little chamber in the abs unit sperate from the regular brake circuit where a motor builds pressure as needed...the air in there gradually gets released into the lines but only when the abs unit is in use...so put the abs on #3...hit the rear brake...engage the abs...pedal gets spongy...bleed and repeat until engaging the abs does not make the pedal spongy
Hey B, I just sent you a message about this topic. after reading this reply my question is, would air in that little chamber affect both front and rear? or just the rear? I ask because my front brakes are perfect and the circuit passes thru the ABS, it's only the rear that is not building pressure.
 

·
Registered
Joined
·
443 Posts
Hey B, I just sent you a message about this topic. after reading this reply my question is, would air in that little chamber affect both front and rear? or just the rear? I ask because my front brakes are perfect and the circuit passes thru the ABS, it's only the rear that is not building pressure.
The two lines are separate circuits going through the abs unit...so air in one would not effect the other....and I'm not sure if it's one pressure chamber that gets bled into either line as needed or if they are two separate...seeing how there's only one motor I'm thinking one pressure chamber and some fancy valving...so...yes...if you had air in the abs units pressure cavity thingy and engaged the abs using the front brake you will put air into that line.... however you are far more likely to trip the rear first and that's where it gets sent...it's also conceivable to think that the rear brake is on top of the unit and air naturally goes there...I'd love to carve one up one day to see inside
 

·
Registered
Joined
·
2 Posts
I changed to Dot 5 fluid which seems to have resolved it (along with taking the rear caliper off and flipping it over to get the pesky bubbles out).
Edit - that should be DOT 5.1 not 5 as pointed out by Shazaam below
 

·
Registered
Joined
·
1,227 Posts
I changed to Dot 5 fluid ...
I hope you mean DOT 5.1 fluid, not silicone-based DOT 5.
All Brembo braking products used by Ducati have natural-rubber base seals that are incompatible with DOT 5 brake fluids.

DOT 5.1 is specifically formulated for use in anti-lock brake systems that require a less viscous fluid to insure fast actuation.
 
1 - 20 of 21 Posts
Top