Rear brake middle piston dragging

I've got a small tube of Bosch Rubber Grease RG17 - wondering if this is good to use where where you've recommended, if not I wonder if it could have any medicinal purposes. [alright, not funny I won't eat it]

Says on the label:
- High performance castor oil based grease designed to preserve and lubricate plastics, rubber and components such as o-rings, valves, diaphrams, cups and seals.
- This product has been developed for use with automotive brake assemblies
- An ideal product for automotive rubber products

There seems a considerable array of plastics and rubbers and a lot to try to understand regarding compatibility of sealants and lubricants; most importantly these brakes [well, you gotta be able to stop] and what preserves and what destroys different materials.

Thought I'd ask before cleaning and applying a bit maybe to the hat brim of the SMC boot, [after brake flush proceedure outlined on this site] even if it's compatible, not sure if that's going to attract dirt or maybe block the drain channel [mine's 09].
 
Are you asking about the sliding guide dowels, or the brake hanger pins?
If the hanger pin(s) are clean and in good condition, they do not require any type of lubrication, and putting anything on them can cause them to collect dirt/grime and start hanging up.
If your asking about the guide dowels that the calipers slide back and forth on, then yes, a very SMALL amount of rubber friendly grease should be applied, however, this means just a FILM applied to the dowel itself. If you have too much on the dowel or the boot, it will create suction, and cause the caliper to stick and cause brake issues.
 
Hello, I had a rear brake dragging problem,done all the things removed pistons new pads,flushed fluid,After seeing your picture of s.m.c with red ring and seeing the small hole I need to know more. Can this hole be flushed? I now ride my bike and check the temp of my rear rotor all the time, warm is what I have, fronts ? Cold. Do I have a problem? Lying on my side rolling the tyre with my foot ,applying the smc by hand applies the rear brake and releases. I cleaned out the piston and I was happy with that,but seeing your small makes me wonder. Is a warm rotor normal? I even made up a spacer block so the smc can’t apply in my tests. Your thoughts please. I am trying to borrow a temp probe by Friday just to see. My bike is 2013.
 
You can diassemble and clean the SMC fully but then comes re-bleeding air out of the system, which needs to be patiently done in the correct sequence.

I did this recently, and you will need to undo the two banjo bolts on the SMC body to remove it; after removing the wheel I remounted the calliper to the fork so I could easily loosen the necessary bolts. You also need to remove the clevis from the SMC pushrod so you can get at the retaining circlip under the rubber boot. The clevis must be refitted at the original position to maintain the calliper in the correct location on the disc. If you hang a weight off the foot pedal (a 4L paint can is perfect) that will keep the line from gravity draining or alowing excess air to enter (but you still have to bleed when you finished).

In addition to the tiny compensation port in the SMC casting, there is also a blue plastic cartridge with mesh screen, one-way valve and another compensation port that can be carefully removed (I levered mine up/out of the casting slowly with a pin), disassembled and then cleaned. See Post #2 above. I used brake cleaner on the individual steel and plastic parts and made sure that the cleaner was jetting through the orifices easily, like cleaning a carb jet, then blew them dry with air. I used silicone grease sparingly on any sliding pins and behind the SMC pushrod boot.

To answer your last question in my experience the rear disc will always be warmer than the fronts, the shrouded location behind a hot motor and surrounded by exhausts guarantees that, but there does seem to be a bit of inherent friction present in this system immediately after application. Bear in mind that for the pressure to release from the two outer pistons, it has to pass back through the compensation ports in the SMC AND the one-way cartridge AND the rear master. I can get a bit over two revolutions of the wheel with a decent shove but that is about it.

My last tip (learned the hard way) is to be mighty careful if you ever remove the larger sliding pin in the back calliper, as it is ridiculoulsly easy to cross-thread it on refitting if done in-situ, which leads to non-parallel sliding pins and a jammed calliper.
 
TerryS said:
You can diassemble and clean the SMC fully but then comes re-bleeding air out of the system, which needs to be patiently done in the correct sequence.

I did this recently, and you will need to undo the two banjo bolts on the SMC body to remove it; after removing the wheel I remounted the calliper to the fork so I could easily loosen the necessary bolts. You also need to remove the clevis from the SMC pushrod so you can get at the retaining circlip under the rubber boot. The clevis must be refitted at the original position to maintain the calliper in the correct location on the disc. If you hang a weight off the foot pedal (a 4L paint can is perfect) that will keep the line from gravity draining or alowing excess air to enter (but you still have to bleed when you finished).

In addition to the tiny compensation port in the SMC casting, there is also a blue plastic cartridge with mesh screen, one-way valve and another compensation port that can be carefully removed (I levered mine up/out of the casting slowly with a pin), disassembled and then cleaned. See Post #2 above. I used brake cleaner on the individual steel and plastic parts and made sure that the cleaner was jetting through the orifices easily, like cleaning a carb jet, then blew them dry with air. I used silicone grease sparingly on any sliding pins and behind the SMC pushrod boot.

To answer your last question in my experience the rear disc will always be warmer than the fronts, the shrouded location behind a hot motor and surrounded by exhausts guarantees that, but there does seem to be a bit of inherent friction present in this system immediately after application. Bear in mind that for the pressure to release from the two outer pistons, it has to pass back through the compensation ports in the SMC AND the one-way cartridge AND the rear master. I can get a bit over two revolutions of the wheel with a decent shove but that is about it.

My last tip (learned the hard way) is to be mighty careful if you ever remove the larger sliding pin in the back calliper, as it is ridiculoulsly easy to cross-thread it on refitting if done in-situ, which leads to non-parallel sliding pins and a jammed calliper.
Click to expand...
 
I appreciate your thaught full reply. Believe me I have gone down this road before. I asumed I was the only one ,I asumed I had an issue and had all the plastic off as my water pump needed attn. with the plastic off I dove right in and did it all. After learning all about the bleeding procedure I bled it all rode it round the block she seemed good,only now am I feeling bad about not removing the smc. Well knowing all the plastic has to come off once more and a big trip coming in a week I need to decide to get into it before the trip or monitor it while on the road. When I feel the rear rotor it seems warm ,not hot. Your thoughts?
 
paul burdett said:
I am trying to borrow a temp probe by Friday just to see. My bike is 2013.
Click to expand...
On my '04,, the rear brake dragged,,, and the rotor was so hot that you could not touch it. Soon after that,,, the smc locked it up and I was getting the bike back home on the back of a flatbed tow truck (courtesy of CAA). And it was like smokin' hot,,, nearly on fire hot,,, btw. So you don't want to go there. I was lucky to not have warped the rear rotor. But,,, after rebuilding and then replacing the smc, temps went back to normal. The rear end is always going to run warmer,,, due to engine heat and normal brake action,,, Just as the drive train is warm too (the pumpkin). But you should still be able to touch it,,, without 3rd degree burns. btw,,,, a digital thermometer is about $60 typically,,, at ctc or Princess Auto,,, but goes on sale for $30 often. I have not checked the rear rotor temp's on my 2012,, but can do so today. It has very little drag and runs quite freely. Feel free to PM me,, if you wish. I would like to help if I can,,, in light of your upcoming trip,,, cheers,, CAt'

MAXIMUM Infrared Thermometer with Mildew Alarm | Canadian Tire
 
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TerryS said:
You can diassemble and clean the SMC fully but then comes re-bleeding air out of the system, which needs to be patiently done in the correct sequence.

I did this recently, and you will need to undo the two banjo bolts on the SMC body to remove it; after removing the wheel I remounted the calliper to the fork so I could easily loosen the necessary bolts. You also need to remove the clevis from the SMC pushrod so you can get at the retaining circlip under the rubber boot. The clevis must be refitted at the original position to maintain the calliper in the correct location on the disc. If you hang a weight off the foot pedal (a 4L paint can is perfect) that will keep the line from gravity draining or alowing excess air to enter (but you still have to bleed when you finished).

In addition to the tiny compensation port in the SMC casting, there is also a blue plastic cartridge with mesh screen, one-way valve and another compensation port that can be carefully removed (I levered mine up/out of the casting slowly with a pin), disassembled and then cleaned. See Post #2 above. I used brake cleaner on the individual steel and plastic parts and made sure that the cleaner was jetting through the orifices easily, like cleaning a carb jet, then blew them dry with air. I used silicone grease sparingly on any sliding pins and behind the SMC pushrod boot.

To answer your last question in my experience the rear disc will always be warmer than the fronts, the shrouded location behind a hot motor and surrounded by exhausts guarantees that, but there does seem to be a bit of inherent friction present in this system immediately after application. Bear in mind that for the pressure to release from the two outer pistons, it has to pass back through the compensation ports in the SMC AND the one-way cartridge AND the rear master. I can get a bit over two revolutions of the wheel with a decent shove but that is about it.

My last tip (learned the hard way) is to be mighty careful if you ever remove the larger sliding pin in the back calliper, as it is ridiculoulsly easy to cross-thread it on refitting if done in-situ, which leads to non-parallel sliding pins and a jammed calliper.
Click to expand...
You are NOT supposed to remove any of the sliding pin(s) for any reason.
There is no reason to remove them. They are designed to pull apart to service.
Folks trying to take short cuts, or remove the bolts on the back side of the caliper, or the large pin, ALWAYS end up damaging either the clips (bending them), damaging the piston(s)/Seal(s) (forcing them in crooked), or most often, cross threading the caliper housing itself, or over tightening the pin which swages into the soft aluminum housing and TILTS the pin, (even though the threads sit square, and it looks normal).
I've had to replace, and instruct folks to replaced several rear calipers because of this error lately.
This is a very expensive mistake you don't want to make.
:WCP1:
 
Catmandu2 said:
On my '04,, the rear brake dragged,,, and the rotor was so hot that you could not touch it. Soon after that,,, the smc locked it up and I was getting the bike back home on the back of a flatbed tow truck (courtesy of CAA). And it was like smokin' hot,,, nearly on fire hot,,, btw. So you don't want to go there. I was lucky to not have warped the rear rotor. But,,, after rebuilding and then replacing the smc, temps went back to normal. The rear end is always going to run warmer,,, due to engine heat and normal brake action,,, Just as the drive train is warm too (the pumpkin). But you should still be able to touch it,,, without 3rd degree burns. btw,,,, a digital thermometer is about $60 typically,,, at ctc or Princess Auto,,, but goes on sale for $30 often. I have not checked the rear rotor temp's on my 2012,, but can do so today. It has very little drag and runs quite freely. Feel free to PM me,, if you wish. I would like to help if I can,,, in light of your upcoming trip,,, cheers,, CAt'

MAXIMUM Infrared Thermometer with Mildew Alarm | Canadian Tire
Click to expand...
 
paul burdett said:
It sounds like I have to pull the smc. I know the piston is free but never was aware of the small hole. Here I go.
Click to expand...
Good luck. I quite like the performance of the linked brake setup but they are complicated and unforgiving. When you get to the small blue cartridge, the screen on one side just presses into a recess groove, and on the other face is a plastic clip that also just presses on, and retains the spring and one-way valve seal. Be gentle and it will come apart fairly easily without any damage, and just snap back together.
Igofar said:
You are NOT supposed to remove any of the sliding pin(s) for any reason.
There is no reason to remove them. They are designed to pull apart to service.
Folks trying to take short cuts, or remove the bolts on the back side of the caliper, or the large pin, ALWAYS end up damaging either the clips (bending them), damaging the piston(s)/Seal(s) (forcing them in crooked), or most often, cross threading the caliper housing itself, or over tightening the pin which swages into the soft aluminum housing and TILTS the pin, (even though the threads sit square, and it looks normal).
I've had to replace, and instruct folks to replaced several rear calipers because of this error lately.
This is a very expensive mistake you don't want to make.
:WCP1:
Click to expand...
All true, my only reason for removing the large pin was to see if it was corroded/dry (it was) prior to a decent clean. My mistake was cleaning and greasing the pin and then refitting it in situ (calliper still on the disc) immediately to see if that resolved the drag. It was remarkably easy to cross-thread; I've been wrenching on my own bikes for more than 30 years and no alarm bells rung while I worked the wrench. As you state, there is no coming back from that without replacing the calliper body. Lesson learned. Don't try this at home, kids!
 
paul burdett said:
It sounds like I have to pull the smc. I know the piston is free but never was aware of the small hole. Here I go.
Click to expand...
I would strongly urge you NOT to do this :nuts:
Your gonna end up doing the whole thing a second time, and risk damaging more stuff when your good intensions fail to fix the issue, and only cause more of them.
The parts in the cartridge are not Supported by Honda, and the screens and O-ring are easily damaged.
The only thing small enough to go through the hole is an Acupuncture needle etc.
Your also probably going to find out the bore is what is damaged and egg shaped (even though it looks clean)
The tell tale signs will be shiny wear marks on the fins of the piston, and flat rubber skirts, which means its been wearing metal on metal etc.
The service manual warns you NOT to remove the Yoke as it is pre-measured from the factory, and you only have a really tiny amount room for error before you block the return port hole.
You can also reverse and put the cartridge in backwards, and in the wrong direction etc.
Too many things can go south if you don't know what your doing.
Several of the folks that have tried, and claimed victory at this, also end up replacing the whole unit a short time later etc.
You've been warned.
Its much easier and cheaper to simply replace the four crush washers, and the damaged unit with a complete new one, and be done with it.
 
paul burdett said:
When I feel the rear rotor it seems warm ,not hot. Your thoughts?
Click to expand...
today's ride weather was a dry 10c. The front rotors were just above ambient. The rear rotor was just warm to the touch, not hot. Certainly,,, 25c would raise the temp's of everything,,, but not to this extent !!
b5HFAT9.jpg
 
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I wonder if it wouldn't be a good idea to keep my little el cheapo infra red thermometer in the tool bag and gun the rear disc / caliper periodically; the read out is worse than useless most of the time, but if you hold the trigger and scan around finding a dull spot in the shade, it can be accurate for a split second; at least alert you, heat seems to be the first indication that your life is gonna suck, the other thing that I'm trying to explore a bit is whatever goes sideways, the front brake system is hydraulically independent; if [maybe more like when] ____ hits the perennial, [and you just left the pig roast food fight] couldn't you scuttle the entire fluid charge in the rear MC / Rear Centre Piston / 2 stage delay valve - front middle pistons / SMC inlet / Proportional Valve / Rear outer pistons... and drive it home with one headlight?
It seems to me that you find yourself out on a dark desert highway with a rear caliper problem, you can either risk killing yourself or destroy everything behind the oil filter.
 
There will be many signs that things are going bad, you won't need your temp gun ;)
There are so many signs where do I begin?
Hard to roll your bike backwards, hard to push off the center stand, howling noise when rolled backwards, vibration in your levers, poor gas mileage, grabby brakes, your helmet hitting the windshield when you just touch the brakes :rofl1: , heat getting really bad, pads wearing crooked like a door stop wedge, or my favorite...."I've got the bike in the middle of an intersection with the red and blue lights flashing, on its side stand because I can move it at all" "what do I do?"
There will be folks who will insist that you can bleed the two systems separately, however, the only correct way to bleed the entire system because its linked, would be to start with #1 and end with #7 in the correct sequence etc.
And as far as your dark desert highway problem....do you really think your going to have the tools, light, and ability to flush and bleed everything in the dark before the coyotes get you?
And that would mean you'd have to carry extra fluid with you?
It would be better to use the emergency release by cracking open #7 bleeder, allowing it to hiss and remove the built up pressure, then try and ride to safety using engine braking and timing, and not touching EITHER brake lever (remember, their linked) If your on a dark desert highway, at night, there should be no traffic, and your only having to dodge the coyotes, wolves, tortoises, snakes, and javelina.....but at least you'll have Hotel California playing on your blue tooth :rolleyes:
 
I guess where I was going with that was cut loose [only in an emergency] the second hydraulic circuit altogether and forego any hydraulic pressure outside of the front two caliper outer piston group, but I get your point much appreciated
 
I'm not offering to be the guinea pig here, but I thought that if there was no fluid /fluid pressure left in the rear pedal/SMC/PCV/rear calliper circuit, the front hydraulic circuit would be unaffected, barring the left calliper being free to rotate towards the fork leg when activated. That might not be too much fun for the SMC components but you'd still have some decent retardation. Or am I missing something?

Likewise the length of the SMC pushrod and clevis; how can that affect where the SMC piston sits at rest so that it blocks the compensation port? Surely that position is down to the piston return spring and the length of the piston and location of the circlip and washer. As long as the SMC/piston is free to rotate, and the pushrod/piston is not seized anyway. Or am I missing something there as well?
 
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