Gonna try to install one of my 2x new SMC units...

[Igofar]

There is an article that @Mellow posted years ago to guide you on the piston cleaning job.

They should look like this when you are done. I extended my pistons before returning them to this position after cleaning. When returning pads to the caliper, ensure that the right pad is set inside the two pins that are circled on the spring clip. As well the clip at the back of the caliper must be cleaned and the pads must straddle the center bar of the clip in order for the pads to move freely with the caliper. Last pic was meant to show the straddle. Thought I had a better one.

FYI your 3rd picture (rear caliper mounting bracket ) appears to have quite a bit of wear on it.
There should be ZERO gap between the steel clip, and the aluminum bracket. When that gap starts appearing, it allows the bracket to shift around and start binding things.
Just saying….

 

[Igofar]

This is what clean should look like, and yes, a bent or dislodged clip can damage a piston if it’s not seated squarely.

 

[SMSW]

This is what clean should look like, and yes, a bent or dislodged clip can damage a piston if it’s not seated squarely.

Larry, in post #159, Dk Shad's third picture shows a tapered, worn brake pad. Is that bad enough to require changing? Could it be the cause of some of his woes?

Were this my bike, I'd probably change the pads at this point because I'd most likely be doing the work during our winter, and I tend to budget $$ ahead for maintenance. Uneven wear bothers me because I take it as a sign something is hanging up somewhere and something needs attention. I understand Dk Shad has limited funds for these things, so if you think he can get away with the worn pad, that is probably the route he will take.

 

[Igofar]

If you’re referring to the last picture, that would be on the wrong side, so it’s my guess, that it is just a shadow.
But in answer to your questions, yes, crooked pads point to something not working correctly.

 

[jfheath]

Just clarifying about those tags on the pad spring. It's actually quite difficult to get this wrong with brand new pads, but with older pads it is a distinct possibility.

This is what the pads look like in the correct position when the caliper is separated.

The sure-fire way of getting them on the correct side, is to pull the caliper towards you as you slide the inner pad (shown) into position - so that the pad is squeezed between the caliper and the brake disc.




Also

That spring clip shown in photo #2 of Igofar's post - 3 up from this one - is supposed to be glued into position so that it is less likely to vibrate and wear its housing. It doesn't need the adhesive - but the glue puts a layer between the two metals preventing one from wearing the other away. The only place that this is mentioned is in the table of lubricants in the workshop manual. They recommend Threebond 1521. I found a more readily available alternative - UHU Max Repair Extreme. Similar properties - flexible polymer, high pressure higher heat rating than 3-bond. Just checkled the UHU site. UHU Max Repair Power seems to be an updated version.

 

[The Dark Shadow]

FYI your 3rd picture (rear caliper mounting bracket ) appears to have quite a bit of wear on it.
There should be ZERO gap between the steel clip, and the aluminum bracket. When that gap starts appearing, it allows the bracket to shift around and start binding things.
Just saying….

I don't see "wear" on the mounting bracket... But I do see "dirt".

I looked at your photos that show some gnarly situations. But presuming I don't have a gnarly situation like some of those shown, then what...?

I don't even know if my pads are binding more than they should at rest (although I think they are).

Do you have 2 photos showing the left and right pads with their resting gap between pad surface and rotor as my photos show...? This would help compare apples to apples. Otherwise, I'm asking if apples are rotten and you're showing my rotten bananas...

Thanks.

 

[The Dark Shadow]

Larry, in post #159, Dk Shad's third picture shows a tapered, worn brake pad. Is that bad enough to require changing? Could it be the cause of some of his woes?

Were this my bike, I'd probably change the pads at this point because I'd most likely be doing the work during our winter, and I tend to budget $$ ahead for maintenance. Uneven wear bothers me because I take it as a sign something is hanging up somewhere and something needs attention. I understand Dk Shad has limited funds for these things, so if you think he can get away with the worn pad, that is probably the route he will take.

The pads have only been on since September last year. They are NOT worn crooked. That is optical illusion from the "ear" of the pad (that goes out to go onto the hangar pin) cling the upper section of the pad.

Just clarifying about those tags on the pad spring. It's actually quite difficult to get this wrong with brand new pads, but with older pads it is a distinct possibility.

This is what the pads look like in the correct position when the caliper is separated.

The sure-fire way of getting them on the correct side, is to pull the caliper towards you as you slide the inner pad (shown) into position - so that the pad is squeezed between the caliper and the brake disc.




Also

That spring clip shown in photo #2 of Igofar's post - 3 up from this one - is supposed to be glued into position so that it is less likely to vibrate and wear its housing. It doesn't need the adhesive - but the glue puts a layer between the two metals preventing one from wearing the other away. The only place that this is mentioned is in the table of lubricants in the workshop manual. They recommend Threebond 1521. I found a more readily available alternative - UHU Max Repair Extreme. Similar properties - flexible polymer, high pressure higher heat rating than 3-bond. Just checkled the UHU site. UHU Max Repair Power seems to be an updated version.

I am VERY confident the pads are not installed crooked.

Responding to something someone else said... They're IS back pressure in the hydraulic system when the pedal or lever is released. We can see this pressure suck fluid from the reservoir when the reservoir is open. This negative pressure must be what pulls the pistons back, since they are not pushed back by springs and they do not recede when a bleeder and/or the reservoir is open.

I only had a cursory look at the clip and spring, but I saw no damage or excessive wear. I did look at the clip to see if there was wear that could prevent the moving pad (ie: the pad on the piston side) from receding, but there was no obstruction or grooving.

As I said in an above comment, we need to compare apples with apples. Showing a whole bunch of things that could go wrong, and a few things that are right, does not answer my question:

In the photo of my pads at rest, should there be a small gap between pads and rotor (ie: 0.2mm or thereabouts), or is it normal for them to be fully flush as you can see in my photos...?

Also, in MY situation, it seems as though the PISTONS ARE NOT RECEDING to allow a 0.2mm gap (of indeed there should be a 0.2mm or similar gap). If this is the situation, then we should be looking at why the pistons are not receding properly. Perhaps these enigmatic D shaped O rings (oxymoron)...?? Do you have a diagram of these D-O rings...?

Let's say, for example, that I get a new caliper ms new bracket, and the brakes perform the same...?? Then what...?

I'll return to the question that must FIRST be answered...?

Are my flush brake pads correct, or should there be a gap at rest...?

Second, what could prevent the cleaned pistons from receding fully...??

Thanks.

 

[jfheath]

@The Dark Shadow - With those tags - I wasn't commenting on your brakes. I was commenting on a previous post from @Esti1300 which stated "ensure that the right pad is set inside the two pins that are circled on the spring clip". Nothing wrong with that statement, but I though that it could be misunderstood - which side is inside ? Is it the inside side of the wheel (which is what I would say) or the inside of the spring - which is what was being talked about. I had a photo, so I was clarifying - not just for you, but for other members reading this thread.

In repsonse to your other question about visible gap. My pads rarely show any gap that is easily visible - not that I get down there and look very often. Most days when I reverse the bike out of the garage, the rear brake pads are lightly scraping the disk surface, or if it has been left a while, they 'howl'. By the time they have reached the end of the drive, they are quiet. This is due to the light coating of surface rust that brake discs acquire when they are stuck in a cold garage where surfaces are able to attract condensation as the summer air cools. The real test is how they feel and sound when you bring it to a halt after the final stop of the day. No noise then. After the final stop, the pads have been in contact with the surface and should have released as a result of the return of the piston seal to its normal shape - rather than by the rotating disc nudging the pistons back in.

I've just checked mine - mild ssshhhh scraping is normal. I've not rideen it for 8 days. Today I could not fit a 0.1mm feeler gauge between disc and pad.

I agree that the pads appear to be at an angle from the photo - but you can never trust a photo. You are looking at the photo almost straight onto the end of the pads, yet you can see the piston face of the caliper body. Then you get the circular distortion of the image from the lens. The pads appear to be worn more at the top - but your evidence says that they are not. I believe your evidence and not the photo.

 

[Sadlsor]

Actually I've never put a feeler gauge on my brake pad-to-disk clearance.
Might do that tonight, just for giggles.
If I feel them binding, or I hear scraping, I address that.
I don't recall ever seeing daylight between the surfaces, when I check for pad wear.

 

[The Dark Shadow]

@The Dark Shadow - With those tags - I wasn't commenting on your brakes. I was commenting on a previous post from @Esti1300 which stated "ensure that the right pad is set inside the two pins that are circled on the spring clip". Nothing wrong with that statement, but I though that it could be misunderstood - which side is inside ? Is it the inside side of the wheel (which is what I would say) or the inside of the spring - which is what was being talked about. I had a photo, so I was clarifying - not just for you, but for other members reading this thread.

In repsonse to your other question about visible gap. My pads rarely show any gap that is easily visible - not that I get down there and look very often. Most days when I reverse the bike out of the garage, the rear brake pads are lightly scraping the disk surface, or if it has been left a while, they 'howl'. By the time they have reached the end of the drive, they are quiet. This is due to the light coating of surface rust that brake discs acquire when they are stuck in a cold garage where surfaces are able to attract condensation as the summer air cools. The real test is how they feel and sound when you bring it to a halt after the final stop of the day. No noise then. After the final stop, the pads have been in contact with the surface and should have released as a result of the return of the piston seal to its normal shape - rather than by the rotating disc nudging the pistons back in.

I've just checked mine - mild ssshhhh scraping is normal. I've not rideen it for 8 days. Today I could not fit a 0.1mm feeler gauge between disc and pad.

I agree that the pads appear to be at an angle from the photo - but you can never trust a photo. You are looking at the photo almost straight onto the end of the pads, yet you can see the piston face of the caliper body. Then you get the circular distortion of the image from the lens. The pads appear to be worn more at the top - but your evidence says that they are not. I believe your evidence and not the photo.

This is helpful and makes sense.

We must all remember (and this comment is not directed to you) that it is VERY difficult to assess problems only by text words and a few photos from oblique angles.

There might not be anything wrong with my brakes. But there might be. From what you stated, I shouldn't be worried that I cannot see visible gap between rotor and pads.

Next, if you would be so kind and able, next time you ride, to NOT use your back brakes for the return trip, and only coast to a stop (using brakes just at the end so that we know brake usage isn't heating the rotor).

As I reported in previous comments, my rear rotor gets warm with ZERO USE...! Last summer, before my brake service, the rotor got HOT... So hot that you couldn't touch it for more than half a second or less...

Presently, it gets warm... from mild to just under medium warm. I can definitely touch and hold. But the front brakes, during a few test runs, have either been cool to the touch or one side only ever so slightly warm. Back is definitely much warmer, but again, not hot.

Thanks eh!

Actually I've never put a feeler gauge on my brake pad-to-disk clearance.
Might do that tonight, just for giggles.
If I feel them binding, or I hear scraping, I address that.
I don't recall ever seeing daylight between the surfaces, when I check for pad wear.

Thank you.

 

[Igofar]

Your focusing on the wrong thing, does your SMC pass the function test now since you have replaced it, and bled the air out of the system?
Does it stop/lock the rear wheel, then release completely again?
How many revolutions does the rear wheel get now with one firm downward push?

 

[jfheath]

What @Igofar said...

But to answer your question. I don't need to go out, I know. It is something that I check every so often - particularly before a long tour and after a long layoff.

Front brakes cool down VERY quickly after being applied. They get an unrestricted cold blast. Rear disk takes much longer to cool down after a few hard stops. Far too hot to touch.
A couple of minutes later they will still be warm but cool enought to touch. I don't know about a minute later - the shortest gap near me between suitable /safe places that I can slow down and stop without touching brakes is 2 minutes. But I don't care if it takes 2 minutes or one minute - they are getting cooler - therefore the brakes are not creating any friction.

The rear brake will normally take longer to cool down because:
1) it is in the direct airflow from the radiator engine underneath the bike.
2) It is right next to the exhaust pipe

And 3) - The rear wheel generates more heat because it is doing the driving forward of the bike. The temperature of the tyre passes through the hub. Have fun with the throttle and half your tyre life, and the wheel will get hotter.

So perform Igofar's tests.
But after you do the wheel spin test, remove your pads and find out how far the wheel spins without the pads in place. Because however good your brakes are, you are never going to get more revolutions than that figure !! In theory it should be the same as his. In practice there may be issues with the bearings that mean that your wheel isn't spinning as far as @Igofar 's

 

[The Dark Shadow]

Your focusing on the wrong thing, does your SMC pass the function test now since you have replaced it, and bled the air out of the system?
Does it stop/lock the rear wheel, then release completely again?
How many revolutions does the rear wheel get now with one firm downward push?

Yes the SMC works. I thought I was clear about this. But the old one did too.

The rear wheel spins about a half turn or so. I'll check this again later and post results.

 

[MidLife]

Responding to something someone else said... They're IS back pressure in the hydraulic system when the pedal or lever is released. We can see this pressure suck fluid from the reservoir when the reservoir is open. This negative pressure must be what pulls the pistons back, since they are not pushed back by springs and they do not recede when a bleeder and/or the reservoir is open.

Fluid sucked from the reservoir is not a good indication of negative pressure ahead of the MC piston.

From the way you've phrased it, it is not clear it is understood that Back Pressure is actually Positive Pressure, not Negative.

As an FYI, most brake systems keep positive pressure (back pressure) on the pistons BY DESIGN, by having the reservoir mounted above the calipers. This is to prevent any chances of the brake fluid transferring back into the reservoir under gravity.

Older cars who didn't have the MC on top of the system had to use a Residual Valve to maintain a few psi on the pistons and prevent such back flow.

 

[Igofar]

Yes the SMC works. I thought I was clear about this. But the old one did too.

The rear wheel spins about a half turn or so. I'll check this again later and post results.

From what your describing, its not at all clear to me.
When I was walking you through the inspection the first time, your SMC failed the function test.
You told me that it did NOT lock the rear wheel, but only slowed it down (failed) and while holding the SMC and applying pressure, you were still able to turn the rear wheel (fail)
Why do you now think that it passed?
Your rear wheel only turning a half turn, is downright screaming that something serious is wrong!
Without clear, honest, and detailed answers, its very difficult for any of us to help you via text messages, phone calls, or watching youtube videos etc.
There are too many things that could cause this for us to try and walk you through it.
You really need to stop throwing money, that you don't have, at solutions to a problem, that you don't know what is.
You really need to take this bike to a shop, or a local mechanic that understands and knows about these bikes.
I know you hate, and don't trust the local shops, but trust me, they probably know a little bit more than you.
I would strongly suggest that you DO NOT attempt to ride the bike, if the rear wheel is only turning a half turn or so, for your safety.
Your rear caliper bracket could be damaged, misaligned, clips bent, your driven bearings could be damaged, your rear wheel could have been assembled in the incorrect sequence, your SMC still may have air in it, your PCV could be the problem, and on, and on, and on.
I don't want to stress you out, but dude, riding a bike with these issues could injure you or someone else.
It may be time to throw in the towel and seek help.
Many folks have explained how the brake system works, and how the seals by design, pull the pistons back away from the rotor, but you either don't want to believe it, or don't fully understand it, as you seem to keep disagreeing with it.

 

[Sadlsor]

I'll have to admit, that after reading 9 pages of discussion and all the comments by TDS, I'm only more confused by it all.

Maybe it's just me, but maybe not.

 

[Gus1300]

I cooked my rear rotor when my smc failed

That's just an unconventional hand warmer!

 

[Esti1300]

I was commenting on a previous post from @Esti1300 which stated "ensure that the right pad is set inside the two pins that are circled on the spring clip". Nothing wrong with that statement, but I though that it could be misunderstood - which side is inside ?

It’s easy for me, the poster, to understand what I mean or meant but I welcome any clarity that can be brought to an instruction or comment. I thank you John for highlighting and providing that clarity as you do often and with great ability. Much respect.

 

[The Dark Shadow]

From what your describing, its not at all clear to me.
When I was walking you through the inspection the first time, your SMC failed the function test.
You told me that it did NOT lock the rear wheel, but only slowed it down (failed) and while holding the SMC and applying pressure, you were still able to turn the rear wheel (fail)
Why do you now think that it passed?
Your rear wheel only turning a half turn, is downright screaming that something serious is wrong!
Without clear, honest, and detailed answers, its very difficult for any of us to help you via text messages, phone calls, or watching youtube videos etc.
There are too many things that could cause this for us to try and walk you through it.
You really need to stop throwing money, that you don't have, at solutions to a problem, that you don't know what is.
You really need to take this bike to a shop, or a local mechanic that understands and knows about these bikes.
I know you hate, and don't trust the local shops, but trust me, they probably know a little bit more than you.
I would strongly suggest that you DO NOT attempt to ride the bike, if the rear wheel is only turning a half turn or so, for your safety.
Your rear caliper bracket could be damaged, misaligned, clips bent, your driven bearings could be damaged, your rear wheel could have been assembled in the incorrect sequence, your SMC still may have air in it, your PCV could be the problem, and on, and on, and on.
I don't want to stress you out, but dude, riding a bike with these issues could injure you or someone else.
It may be time to throw in the towel and seek help.
Many folks have explained how the brake system works, and how the seals by design, pull the pistons back away from the rotor, but you either don't want to believe it, or don't fully understand it, as you seem to keep disagreeing with it.

I NEVER disagreed with people explaining about brake D-O rings.

Please do not put words in my mouth.

Can I seriously bring my bike to the shop that put the wrong spark plugs in my bike and told me that the back brakes were perfect when they were clearly binding (too hot to touch when not even using them, and the rear wheel would only spin a quarter turn, and yet they wouldn't listen to the instructions I shared from forum members)?

Can I seriously bring my bike to a shop where the fellow put an adjustable wrench onto the SMC bracket and wrenched it forwards to do the check that you describe...?

Can I seriously bring my bike to a shop, one hour away, that added 2 decent sized scratches on my rim when changing my front tire, and the worker took my bike out for a ride just to check out my bike without asking me...??

This is the hicksville where I live... The biggest "city" in Atlantic Canada.

I asked if someone has a diagram of the D-O ring mechanism... I understand the outer parts... But I don't understand the inner parts...

How can brake pistons that push out with hydraulic pressure not recede without hydraulic vacuum...?

FWIW, the test to see if the SMC would freeze the back wheel worked last August or September with the old SMC. Work just one human being, I cannot squeeze the SMC hard enough at the same time as spinning the back wheel. I'm not an octopus and perhaps don't have superb grip strength. If I lightly squeeze the brake lever, the front brakes engage but don't lock. If I tightly squeeze the lever, the brakes lock

 

[The Dark Shadow]

From what your describing, its not at all clear to me.
When I was walking you through the inspection the first time, your SMC failed the function test.
You told me that it did NOT lock the rear wheel, but only slowed it down (failed) and while holding the SMC and applying pressure, you were still able to turn the rear wheel (fail)
Why do you now think that it passed?
Your rear wheel only turning a half turn, is downright screaming that something serious is wrong!
Without clear, honest, and detailed answers, its very difficult for any of us to help you via text messages, phone calls, or watching youtube videos etc.
There are too many things that could cause this for us to try and walk you through it.
You really need to stop throwing money, that you don't have, at solutions to a problem, that you don't know what is.
You really need to take this bike to a shop, or a local mechanic that understands and knows about these bikes.
I know you hate, and don't trust the local shops, but trust me, they probably know a little bit more than you.
I would strongly suggest that you DO NOT attempt to ride the bike, if the rear wheel is only turning a half turn or so, for your safety.
Your rear caliper bracket could be damaged, misaligned, clips bent, your driven bearings could be damaged, your rear wheel could have been assembled in the incorrect sequence, your SMC still may have air in it, your PCV could be the problem, and on, and on, and on.
I don't want to stress you out, but dude, riding a bike with these issues could injure you or someone else.
It may be time to throw in the towel and seek help.
Many folks have explained how the brake system works, and how the seals by design, pull the pistons back away from the rotor, but you either don't want to believe it, or don't fully understand it, as you seem to keep disagreeing with it.

FWIW, the back wheel spins nice and freely.

Also, I don't think there are bad questions.

Questions indicate both areas where a person is lacking understanding but also areas where there is a desire to learn.

I'm not going to reread all my posts, but certainly a few of my questions AFTER having done the procedure were to ascertain whether my back brakes were working as they should. Hence my questions, "Should the back rotor get warm?" "How warm should the rotor get?" "How much space should there be between the pads and the rotor?"

These questions should have been be easy to answer and easily help me determine if my brakes are working properly or not.

It seems as though my brakes are now functioning properly.

So I am thankful to EVERYONE who chimed in to help me out. Kudos!

FWIW, I've been through a lot of socio-psychological pressure and some physical challenges in my life... And I'm still in the midst of a lot of issues. And the way I turned out in the aftermath is such that I get psychological paralysis, anxiety, and stress doing new things that I don't fully understand. And, other than changing some outer stuff (handlebars, screens, mirrors on my former Shadow 750, etc), I don't particularly enjoy automotive maintenance. It is therapy for some people, but for me, it is like a trip to the dentist. Having a working motorcycle is my therapy and a way for me to relieve my burdens. But I live in the backwater of the world. People with get up and go got up and went. There's few good motorcycle techs here. None trustworthy that I know. Hence, having problems with my holy grail of bikes does really really bad stuff to my psychology. So give a man a break... Let him have his therapy, and don't suggest he ride a "simpler" bike. No matter what bike I own, my psychology won't change nor will the lack of good moto techs in my area.

None of my questions were wrong or bad.

If I ask about how to cut an apple, describing how to peel a banana isn't very helpful.

I will repeat to you, Larry... I very much appreciate your efforts to help, I recognize your willingness to help and your desire to help me through this process, and I'm truly sorry if my psychological state was tough for you. But that's just the damaged goods that I am...