Hello tech gurus.
I just bled my rear brake on my S2R800. I did all the fancy move the caliper around business, got all the air out, etc. etc.
I have plenty of bite, plenty of stopping power... Problem is, now the pedal is SUPER stiff. I have to push really hard, and the pedal only moves about 1/4 of an inch, and it's full-on, lock up the wheel stopping power...
Any thoughts on how to get that nice, smooth, consistent pedal feel back?
I also have rizoma rearsets. could these be leading to some problems?
Do you have any freeplay in the pushrod?
The master requires some freeplay so that the piston isn't covering the bleed hole.
Running with the bleed hole covered will lead to bad things.
hmm. not sure.
is the bleed hole located underneath the rubber cover that the pushrod slides into?
there seems to be some freeplay.
what sort of bad things could happen?
would these bad things happen if, say, i were to completely bleed rear brake with said bleed-hole covered?
Quote from: Speeddog on April 03, 2009, 12:52:29 PM
Do you have any freeplay in the pushrod?
The master requires some freeplay so that the piston isn't covering the bleed hole.
Running with the bleed hole covered will lead to bad things.
Eggzakly what I was thinking. Not enough free play can lead to a flaming rear brake. I don't know am exact spec, but make sure the fluid returns (spout of fluid when lever is released) and add a little more.
it appears that here is no fluid returning, but my rear brake is definitely not engaged. wheel spins very freely unless i engage the pedal.
what is the solution for the fluid not returning to the master?
Shorten the push rod until fluid returns, then a little more. Loosen the lock nut on the pushrod and turn the pushrod until you get the free play. Ah, found a spec. At least 1.5mm.
Quote from: howie on April 03, 2009, 01:41:22 PM
Not enough free play can lead to a flaming rear brake.
I have had this happen! Do as the man says!
will do!
as stated, i did put the new rearsets on.
i will re-adjust the push-rod as needed, and might run through the bleed procedure one more time to be safe. it's not that hard or time consuming.
i wanted to move rearsets back a notch anyway ;D
i'll keep you guys posted!
thanks again for the help, i report back with any further problems.
Quote from: MrIncredible on April 04, 2009, 05:00:21 PM
I have had this happen! Do as the man says!
+1!
DOT4 makes a pretty green flame, if you really want to find out for yourself... :(
Hah. Sounds cool!
I'd prefer to find out by some other means though. DOT4 Molotov anybody?
Quote from: corey on April 07, 2009, 06:30:36 AM
Hah. Sounds cool!
I'd prefer to find out by some other means though. DOT4 Molotov anybody?
but half the fun of it is scraping the melted speedo sensor's plastic from your rim... and replacing a whole lotta parts because you didn't put enough slack in the MC's pushy-doo
still haven't gotten around to fixing this yet, but i haven't been riding.
i'll be sure that my MC pushy-doo has plenty of slack?
hah.
I ended up backing the rod all the way out on mine (out of paranoia)... I coulda sworn I had enough slack when I installed my rearsets.
Well. No luck still after an entire container of DOT4 and a whole lot of swearing.
I even drained the entire system and started from scratch.
Once the system is full, i do a final bleed, close the screw, release the pedal. Then i pump it up for pressure, takes only 1, maybe 1.5 pumps.
Perfect, the wheel stops like a make the beast with two backsing ROCK. But then when i let go of the pedal, the fluid does NOT return to the reservoir. Next time i go to pump the brake, the system is already filled to capacity, and it cannot move more fluid in, so i get instant wheel stopping power in about 1/4" of pedal. Not Good.
No matter what i tried, i could not get fluid to return back to the reservoir.
The hose is not crimped, nothing inside it, i blew through it to make sure. The system is clean, all fresh fluid.
Pressure will release off of the rear brake, but fluid will NOT return.
If i push the pads away from the rotor with a flat head screwdriver, the fluid DOES return. But it will NOT when i just simply release the pedal.
Anyone have any thoughts? I am make the beast with two backsing stumped, i have no clue what to do...
I really want to get on the road :( :( :(
It sounds like your brake is bled properly. The problem is like stated above - the push rod needs to be adjusted shorter. When the brake pedal is released, there should be some free play between the rod and the slave piston. The piston needs to back out far enough to uncover the internal bleed back port for the fluid to return. I don't think you'll see a lot of fluid return, not like when you push the pads back. Does the lever move easily?
I've had no issues with my S2R rear brake, however, I went through a couple of rear masters on my old 916 which had a similar setup, the problem was corrosion of the pushrod, take the master off and remove the rubber boot then clean out the gunge which tends to collect in there and clean everything up, corrosion means the rod doesn't slide through the seal smoothly and will stick, if it sticks on you'll have obvious problems, if it sticks off then the continued pressure of using the brake may blow the seal. If the pushrod gets too crusty it also tear the seal leading to leaks and air in the system.
This might not be a factor on your bike but worth checking anyway.
Quote from: Bill in OKC on April 09, 2009, 08:40:57 PM
It sounds like your brake is bled properly. The problem is like stated above - the push rod needs to be adjusted shorter. When the brake pedal is released, there should be some free play between the rod and the slave piston. The piston needs to back out far enough to uncover the internal bleed back port for the fluid to return. I don't think you'll see a lot of fluid return, not like when you push the pads back. Does the lever move easily?
Push rod has more than enough free play unfortunately. I have it backed out entirely.
The lever is rock hard, unless i push fluid back into the reservoir by spreading the pads.
It justt seems like fluid does NOT want to come back through the bleed hole. There is something preventing it from happening.
Does anyone have any internal knowledge of these Master Cylinders? Is there a seal or something that could go bad?
Could it be something OTHER than the master cylinder? I can't really think of anything else it could be, because fluid flows free and easy through everything while the bleed screw is cracked open. Fluid just won't go backwards back through the master into the rezzy. Even with the cap off.
Could this be a caliper issue? Is there something that makes the caliper spread back open that forces the fluid back through the system? or is that just a natural thing that happens with hydraulics?
I didn't use the wrong fluid did i? DOT4 correct?
Where is the bleed hole located on the M/C? Is it something i can get to and clean/clear out manually?
Should i just buy a new M/C? Are there aftermarket options that are less prone to failure?
You may have to disassemble and check. Yes, you used the proper fluid, but what about previous people? If someone before you introduced petroleum product into the system the seal is swelled. The vent port can also be restricted. Rebuild kits are close to impossible to find. New OEM replacements are inexpensive.
http://www.yoyodyneti.com/Category.aspx?CategoryID=3007 (http://www.yoyodyneti.com/Category.aspx?CategoryID=3007)
PS11B is your master.
The caliper can be a problem also, but not likely. If extra force is needed to retract the piston that can cause the problem. In normal use twisting of the piston seal is what returns the piston. If in doubt, let someone with a more educated feel check.
Thanks for the reply howie.
I bought the bike with only 2600 miles on it, and I'm pretty sure the rear fluid that was in there was the original.
I did some searching around on some other ducati forums, and found this statement:
"So lets try this. IF the compensating port is blocked, blocked because either the piston rod is screwed too far out of the clevis, OR if the screw that contacts the brake light switch is screwed out (towards the switch), then fluid WILL NOT return to the reservoir."
If my brakelight switch screw were too far out, and the rod returned to the resting position it could achieve within the area allowed by the brakelight screw, the vent port would remain obstructed by the rod. If the vent port were to remain obstructed, would pressure applied to brake when pressing the pedal down STAY pressurized? Thus creating some free-play in my pedal that i THINK i have, but actually may not?
Edit: After thinking this through, i have even tried REMOVING the rod entirely after engaging the brake. The pressure still does not release. The pressure builds and builds, but will not release/return fluid.
Is it possible that the M/C just will NOT allow fluid to return?
It's like a vacuum is forming inside the system...
Quote from: corey on April 10, 2009, 06:39:24 AM
Is it possible that the M/C just will NOT allow fluid to return?
something is keeping the piston from returning to its resting position. It looks like time to take the master apart and check it out. Dirt, corrosion, broken internal spring, ??? if there is nothing external pushing on the piston then it must be internal.
some more information.
if the bleed screw is cracked, the pedal works as normal. Full push, full release.
the push-rod (bill is that what you are calling piston?) is at the rest position, with plenty of play.
on this caliper, do both pistons move? or only one.
i remember only being able to move one brake pad while prying the pads apart.
is it possible that one of my pistons on the caliper could be stuck? causing the fluid to remain "mostly" in the system, but allowing just enough retraction to disengage the brake (i.e., the OTHER piston retracting a bit)?
i'm not sure how this could have occured though, as the caliper has never squeezed onto anything aside from it's specific rotor...
any guides out there on disassembling the master?
It almost sounds to me like you got used to riding around with some air in the system. Now your brake is bled and working right, but you're not used to the positive action. But this is just a guess from long distance.
If the bleed port wasn't bleeding, I think the brake would pump up with each stroke and the tire would stay locked when the brake pedal is released. From your description it doesn't sound like the wheel is locking up. If everything is working correctly the pistons do not move very much at all, there is not much fluid going to the caliper and there might not be a jet of visible return fluid in the reservoir when the pedal is released.
The seals in the caliper are supposed to flex a bit when the brake is applied, allowing the pistons to move then act like a spring to pull the pistons back very slightly.
Howie, correct me if I'm wrong but if the bleed port isn't open, he wouldn't be able to force fluid back to the reservoir by moving the brake pads with a screwdriver?
I just did a rear brake bleed on my S2R 800 yesterday. From what I've heard so far corey, your caliper does not seem like the source of the problem. Your problem is in the rear master cylinder if there is one..Have you gone for a ride and tried the brake or is this all "bench" testing..
As a reference point for what it might be worth I just went out and looked at my M620. I don't know what the spec is, but moving the pedal by hand I get about 1/4" of motion to take the slack out of the actuator rod. Then about another 1/4" of actual M/C piston motion (measured at the boot toe end of the brake pedal) before the brake is fully engaged. There is no visible activity in the reservoir when the pedal is released.
EEL:
I have ridden the bike.
It rides fine, there is no lockup of the wheel, and the caliper is not engauged unless i push the pedal.
Langanobob:
Your measurement experience sounds about exactly the same as mine.
I wonder if you are correct about me getting used to running with air in the line.
Can anyone else add any feedback as to how far their push-rod moves from zero-engagement to full-engagement?
My pedal just seems very stiff, but i guess it could possibly be the way it is SUPPOSED to be.
Previously, my pushrod would travel roughly 1" to 1.25" when using the rear brake pedal.
I think Langanobob may be onto something, you may be trying to fix something that ain't broke. Go for a nice ride, use the back brake and see what happens. Be cautious though, the back brake is ineffective enough at speed that you might not feel the drag, but you can build enough heat to cook your back brake. I know someone who cooked his back brake twice on a 748.
Quote from: Langanobob on April 10, 2009, 08:10:02 AM
<snip>
The seals in the caliper are supposed to flex a bit when the brake is applied, allowing the pistons to move then act like a spring to pull the pistons back very slightly.
Nice explanation [thumbsup]
Howie, correct me if I'm wrong but if the bleed port isn't open, he wouldn't be able to force fluid back to the reservoir by moving the brake pads with a screwdriver?
If the port is completely restricted one would have so put enough force on the piston to get the seal to bypass, possible with the combination of leverage and hydraulic advantage. If one did accomplish this he would most likely notice brake fluid escaping through the rear of the master. Partially restricted, maybe. .Therefore you are correct. One way to catch a master that is not releasing is to bleed the brake(s) affected after it binds. The brake instantly releases, bingo!
The spec I gave you is for the push rod, not the pedal. You will have much more travel at the lever.
Sounds like I am beating a dead horse... or I guess a live horse now?
like i said, the brake is not engaged unless the pedal is depressed. the actuator push-rod has about 1/4" free play (to be safe, it's a little more than spec'd 1.2mm), and then about another 1/4" to 3/8" of travel before i am out of pedal. A very firm braking action indeed.
By everyone's description, it doesn't sound as if my bleed port is obstructed, since I am EASILY able to force the fluid backwards by spreading the pads inside the caliper. It doesn't require much effort at all. I can do it by squeezing with my hand if a I really get into it.
My only worry is that if there is an obstruction, when the bike gets warm, the fluid will expand and lock up my back brake. I guess i will have to be sure there is not too much fluid inside the reservoir. Is this a legitimate concern?
I will ride it a few times and see what i get, but as stated, it sounds like i actually fixed it, and it's now working like it should, and I'm just used to a little bit of a mushy pedal (like a car) and not the stiff nature of the rear brake on the bike.
I'll keep you guys posted. I'm going to have my dealer check it out when it goes in for the 6k service in early June.
I appreciate all the thoughts and help, this could be a great informative thread for the future!
Cor
Not sure if I can be of help, but your symptoms sound like 2 things that come to mind. Brake hose going to caliper. If they fail internally they can act like a one way valve. The caliper may not release, and or hydraulic supply maybe cut off. I didnt read all the pages, but i am assuming your removing the rear brake caliper to bleed it. The bleeder screw must be bled as it faces upwards. You would never know if the hose was at fault since your twisting the whole thing as you bleed it. It may only act up when installed since the hose falls into its natural bend. Was any fluid other than brake fluid used? If thats the case, every rubber seal and that comes in contact with the fluid is toast. That includes caliper, master cylinder and brake line. One last thing, you MUST use D0T 4 fluid. DOT 3 does not have the temperature rating that bikes need. Once things heat up while riding, I have heard that the DOT3 can actually apply the brake because of fluid expansion and boiling point.
Quote from: woppini on April 10, 2009, 03:54:14 PM
Not sure if I can be of help, but your symptoms sound like 2 things that come to mind. Brake hose going to caliper. If they fail internally they can act like a one way valve. The caliper may not release, and or hydraulic supply maybe cut off. I didnt read all the pages, but i am assuming your removing the rear brake caliper to bleed it. The bleeder screw must be bled as it faces upwards. You would never know if the hose was at fault since your twisting the whole thing as you bleed it. It may only act up when installed since the hose falls into its natural bend. Was any fluid other than brake fluid used? If thats the case, every rubber seal and that comes in contact with the fluid is toast. That includes caliper, master cylinder and brake line. One last thing, you MUST use D0T 4 fluid. DOT 3 does not have the temperature rating that bikes need. Once things heat up while riding, I have heard that the DOT3 can actually apply the brake because of fluid expansion and boiling point.
Thanks for the reply woppini!
To answer your questions...
I'm pretty sure the line is fine, as I am able to bleed plenty of fluid (an entire canister in fact) in both the mounted AND unmounted, upside-down bleeding position. I have also checked to see if fluid would go back through on it's own by leaving the bleed screw cracked and releasing the pedal to see what would happen. plenty of suction back the other way.
As far as brake fluids, the stuff that was in there looked original, and i used DOT4, high-temp specific stuff.
As stated, I'm pretty sure i got everything right, it just "feels" different to me than what i'm used to, which is a spongy pedal i guess...
the master cylinder is mounted at an angle. If there are air pockets in there, they will always stay toward the highest end. Have you tried removing the master cyl, and keeping it level? Crack the bleeder lose and let it gravity bleed or take a measurement of how far the push rod moves in with the master cyl installed. When you remove the cylinder to hold it level, push on the rod the same amount you just measured. Crack open the bleeder each time you push in the rod, and close it each time you release the rod. The reason why I mentioned taking a measurement is because you can push the master cyl rod too far in which could cut the seals.
so today i took the bike for a VERY short stroll around the block a couple times (had family stuff to do... it IS easter after all) and all seemed well.
the rear brake was very responsive, and i had a very nice pedal feel.
just for shits, i compared the pedal feel and pushrod travel to that of my girlfriends gsxr600. it's almost identical.
i think i was just being pissy about the new pedal feel..
turns out my brake actually WORKS now!
thanks for all the help guys, i feel like a mjaor dipshit.
2 page thread with almost 300 views of me trying to fix something that wasn't broken. genius.
Please don't get down on yourself at all.....given the consequences of doing it wrong being careful and cautious and seeking the advice of others was prudent.
And after taking my S2R out for a jaunt yesterday with NO rear brakes, well I'll be going through the same process but now armed with much more information.
So thanks... [thumbsup]
no prob! hopefully this one proves to be helpful for lots of folks.
these rear brakes seem like a major pain for a lot of people.
Quote from: corey on April 13, 2009, 07:10:45 AM
no prob! hopefully this one proves to be helpful for lots of folks.
these rear brakes seem like a major pain for a lot of people.
only when they explode ;D