Rear brake issue

[Igofar]

I just opened 4 new rear caliper brackets and they are all completely smooth with no “damage” or “flute” marks.
Just a guess, but perhaps the assembler didn’t follow the correct procedure at the dealership, after all these are usually 16 year old kids who only break down shipping crates, wash bikes, and put things together when the technician’s are too busy.
The marks you see are Damage, plain and simple.
They can cause howling and dragging issues.
When the SMC starts dragging, or putting pressure on the front clip, it wears away and slopes downward.
The clip then gets clearance or a gap so the clip can tilt, for a lack of a better term.
And if the pads tilt, they bind, binding causes chatter against the stopper plug etc.
Think of “grabby rear brakes” every time they grab or bind against the rotor, the caliper slams against the stopper plug bracket.
If you have 150,000 miles on your SMC, and see these signs, it’s telling you something is wrong.
If everything is as good as you think, I’d go buy a lottery ticket, as you are extremely lucky.
I have a 55 gallon steel drum full of frozen and failed SMC units and rear caliper brackets.

 

[MidLife]

If you have 150,000 miles on your SMC, and see these signs, it’s telling you something is wrong.

Mr Shadow's point was:

--- Marks were there a 3K, with no change in their pattern after 150K.

What could be this hidden defect that has caused absolutely no issues for @Andrew Shadow over about 240 000 Canadian miles?

 

[Igofar]

So you’re pointing out that he found/observed the damage at 3k miles, and the damage has not gotten worse.
What you’re missing is that it is still damage.
I still get people coming in with the rear pads completely gone, metal on metal, and tell me the bike works fine, so they just continue riding it that way.

 

[Andrew Shadow]

these are usually 16 year old kids who only break down shipping crates, wash bikes, and put things together when the technician’s are too busy.

Firstly, I am in no way challenging your skill or knowledge. I am only trying to figure this out for my benefit. The facts that I have seen have ked me to a different conclusion than yours, and I want to know why that is.

Secondly, the rear wheel is installed at the factory by Honda not by the dealer, let alone a 16 year old at the dealer. We both know this so this is a non-stsrter.

I don't agree that this is plain and simple. If it was I would have suffered some kind of brake failure tens of thousands of miles ago, and I have not.

Imagine if you will, hypothetically if you must, that none of the damage or symptoms that you have described are present. There is no deficiency and no sign of brake trouble at all. There is absolutely nothing other than these marks. Then what do we conclude? Do we replace the SMC and the rear caliper bracket anyway based solely on these marks and no other supporting evidence of a problem or impending problem? In my case, had I done that I would have robbed myself of at least 125,000 KM of service life of these parts and counting because there they are still in service and there is still no evidence of a problem. I have none of the symptoms that you have described. I never have had and I still do not. These marks were there at 3,000 and they are still there now. If they are an irrefutable sign of impending failure of the bracket or the SMC it should have manifested itself somewhere over the past 100,000 plus KM, but it hasn't.

The symptoms and reasons for them that have been cited are not present on my bike, they never have been. They were not on my brother in-law's either. Based on that I can't help but wonder if these marks are the result of something else.

I freely admit that I still don't know what that something else might be, nor do I don't think any less of anyone else who admits the same.

 

[Andrew Shadow]

So you’re pointing out that he found/observed the damage at 3k miles, and the damage has not gotten worse.

No, I am questioning what is the cause of what is cited as damage.

I still get people coming in with the rear pads completely gone, metal on metal, and tell me the bike works fine, so they just continue riding it that way.

I am asking this question out of a genuine desire to understand what currently doesn't add up, even when held up against your criteria. Insinuating that I am not capable of seeing a brake defect if it hit me in the face and therefore can't see this one doesn't move that effort forward or add support to your claim.

 

[Igofar]

I would never imply that you could not see if your bike has brake issues, and no disrespect was directed or thrown your way.
I am sorry if you feel so.
I would love to see three photos of your rear caliper and pads (rear/left side/right backside) showing detail of the front pad retaining clip.
You could have damage and not even know it.
I would also like to see your SMC piston movement as well.
Not pressing on it under pressure, but with the PCV bleeder open, and then manually pressing the piston In the bore.
If your piston goes in about 1/2 of an inch smoothly, then returns on its own, I will agree the bore is free and not obstructed.
If the piston does not do that, your function test is deceiving you.
Also, remove the rear brake line and see if it is jammed with jelled up crap.
In simple terms, think of it this way, the lower bout on your guitar has a crack you just found, and it never seems to get worse, it does not sound any different, so you just keep playing.
Nothing wrong with that if that is what you choose to do, but does that mean it is not damaged?

 

[jfheath]

Not taking sides here - I'm curious about the flutes because although I have my own thoughts as to why the damage looks like the inside of the bore of a Walther PPK, I am not entirely convinced by my own 'explanations' !

But just because it was assembled at the factory does not mean that it was done correctly. Your 3000 mile damage could still have been caused by incorrect assembly. It hasn't got worse because you re-assembled it properly ?

My own ST1300 was brand new. It had an assembly fault which left me stranded after 7 miles.

 

[Chris09]

The only other thing that could wobble is the caliper bracket itself. That would require the axle to move - which it cannot. [excerpt from post 96].
So this is brings me back to kind of a gulp - sick in the stomach feeling, maybe why no one should work on their own vehicles.
There is some clearance between my axle and bore and swing arm, will take and show a closer look later.
There is also some clearance between the axle and the corresponding bracket bore which I haven't had a harder look at yet.
Seeing the flute mark patterns didn't particularly surprise me, I've seen them as described as a result of milling processes before as described by Mark.
What concerned me was their bright clean finish; I think I took a photo of the stopper pin end with the axle, bracket and stopper hand tight assembled and there is clearance on either side of the pin that I would have expected to have some dirt or grease or darker oxide in - if there is no appreciable relative for and aft movement of the bracket along the pin.
I heated the bracket just in case it's of an alloy with a high coefficient of expansion, I could see no appreciable change to 160, I like 160 because I've never felt the area around the the rear caliper / bracket / wheel / swingarm too hot to touch during the finger temperature tests conducted variously over the 29,000 - [current] 46,000 [edit] kilometers I've put on the bike.
I have to wonder if the axle is shifting laterally [back and forth] relative to the swing arm and if the bracket is shifting similarly relative to the axle.
I wish I would have used a torque wrench when initally removing the axle [correction] nut and the stopper bolt, but I'm satisfied these would have been consistent with the 80 and 51 odd lbs at installation.
I compared the washer against the glaze pattern at the swing arm and the glaze pattern fits within the washer OD.
I couldn't find any reference to clearances between the axle and the swingarm in the service manual, I'd be interested to hear from others that have changed their tires and brakes if they remember whether the axle fits tightly in the swingarm or if there feels like there might be a slight bit of clearance.
Could it be possible that everything along the line is assembled correctly, but that the axle scrolls slightly within the small amount of clearance between the swingarm bore, and the bracket does the same, taking up that bit of stopper bolt pin end clearance at either end under different conditions.
I should acknowledge that I'm also going to take a harder look at the various aspects of the bracket and clip and compare to the photos provided by Larry in the previous posts.
I'm also going to set everything up without the bracket and spin the wheel, I never got the number of rotations ever since getting the bike five years ago and there's been no change in how far the wheel travels when the test is done over that same period. Maybe the bearings are garbage [and were garbage when I got it, or assembled incorrectly].
I've had identical factory assembled original combustion blower assemblies where one fan wheel rotates nicely on the drive end bearing but two others are as close to perpetual motion as it gets. the former requiring a higher minimum VFD setting to avoid stalling. Still works the same years afterward, just not as high of a turn down capability [who cares, I'm the only one that knows... ]
Still just throwing it all out there and taking it all in. Taking a hard read on all of these posts good to have the help and experience of everyone.

 

[jfheath]

I couldn't find any reference to clearances between the axle and the swingarm in the service manual, I'd be interested to hear from others that have changed their tires and brakes if they remember whether the axle fits tightly in the swingarm or if there feels like there might be a slight bit of clearance.

There should be no gap.

Whatever image is in your head about axles - it sounds like it is wrong.

The axles isn't just an axle - it is a draw bolt. For the rear wheel, the axle goes in from the right hand side and it pulls everything together and clamps it tight between the two arms of the swinging arm. Everything on that axle is clamped solid.

The bolt passes through the final drive mechanism. You don't have to worry about that- but there are parts in there that must be present.



In the picture, you have to imagine that the front of the bike is facing in the direction of the bottom left corner.

The parts outline in red are all hidden behind the plate that secures the final drive spline. Part #17 is a massive circlip that holds the plate in place. Part #1 are the rubber blocks that cushion the schock of the power train rotating as a result of engine power meeting the wheel which is attached to the road by the tyres.

The components outlined in red are all part of the final drive - The only bit that you can normally see is the drive spline - just protruding to the right of part number 6. That spline is the part that pushes into the final drive hub. Final drive body which forms the back end of the right swing arm fits to the right of par t#24 .

So concentrate on where the axle goes in the diagram. Through the two flange bearings #18, through the distance collar #6 , throught the left wheel bearing #20, through the distance collar #5, the main wheel bearing (double race)#19, through the spacer #3, through the left hand swing arm leg, the washer and the large nut. Remember the left side of the wheel is where the brake disk and axle nut is shown.

When the axle nut is tightened, all of these components are clamped together. Solid. The spacer #5 is often thought of as something that floats around loose between the bearings. Not so. It is firmly clamped onto the inner race of the bearing. Turn one bearing, the other should turn with it. The wheel should be free to rotate because the outer shell of the bearing is driven into the cast hub. The wheel will rotate freely. But because all of the components on the axle are clamped together, there is not room for anything to slide left to right.

The caliper bracketgoes to the left of part #3 - the distance collar, the swing arm left side is next, and the washer and the nut fit after.

You can see this sort of thing on the animation that I did for the front wheel. Same idea - as the axle bolt is tightened, all of the parts are drawn together.

I'll put the link in later. https://www.st-owners.com/forums/th...heel-install-and-front-axle-animation.161738/

If you have got any gaps, then you might have a part missing. A typical part to forget to put in is the spacer. #3.

Collapsed bearings might be an issue - but the bearing inner race will still be in place on the axle so it will not create a gap - althought he wheel would wobble about a bit. Unlike the front axle where the fork legs have a little lateral movement on the solid axle, the swing arm is exaclty the correct width to accomodate all of the parts - exactly.

 

[Chris09]

Thanks for all of that John which is going to be of immense help looking further into the situation. Good start for when I get back to review all the links in the chain.

I wonder if through initial and successive tire changes it isn't inevitable that someone does something wrong.

The clearance aspect is as depicted below, to my recollection there were no clearances or gaps axial to the axle, no side to side detectable with the wheel / tire in place, but as I say we'll see in the next step.

So here's a couple of shots of the situation I was referring to

 

[jfheath]

Ah - were you talking about the apparently large hole through which the axle sits ?

I thought that you meant that there was a gap either side of the bracket - which is what I was talking about.

Must read the question John

 

[Igofar]

What about the rubber damper cushions beneath the spline plate? They get hard, and the little raised pedestals on the top get deep impressions in them causing slop, which might explain some movement.
What about the inner o-ring behind the spline plate, I have found these damaged and metal to metal wear on the boss of the wheel hub?
Just throwing questions out there.

 

[Andrew Shadow]

@Igofar
Larry, we seemed to have strayed from what I don't understand and what I am asking about. I am not challenging your diagnosis or your experience. I am not debating whether you find deformed brackets or not, or whether replacing the bracket and the SMC fixes the problem. I accept all those things as a given, you have many proven results to back this up. What I don't understand in this scenario is how the stopper bolt can create spiral witness marks. This is what I am asking about and hoping that you, or @jfheath or anyone else can explain.

In a scenario where the SMC is good and the caliper bracket is not deformed, and if we accept that the brakes are functioning properly, witness marks on the caliper bracket can only be created by the stopper bolt where it comes in to contact with the bracket as it moves vertically as it is supposed to do. The bolt is round and the slot in the bracket is not contoured to match tightly like a bolt hole is. This leaves only a fraction of an inch of contact at the upper and lower radii of the bolt. Because the bracket moves vertically, not horizontally, the point of contact remains restricted to this very small contact area and it is perpendicular to the opening in the bracket. These wtness marks are the result of the vertical movement of the bracket against the stationary stopper bolt, there is no lateral movement between the two.

Now we introduce a scenario where the caliper bracket is twisted. The contact area will change and it will no longer be perpendicular to the slot in the bracket. Because the stopper bolt is still in the same position, and the bracket is now twisted, the witness marks will now be angled to match the amount of twist that there is in the bracket. There is still no lateral movement between the two so it will still be limited to the very small contact areas at the top and the bottom of the bolt.

Tha above all makes perfect sense to me. What I don't understand is;
1- How are these witness marks present outside of that very limited contact area? If they are present in parts of the opening where the stopper bolt never makes contact, what caused them?
2- Nothing in the operation of the brake causes the caliper bracket to rotate around the stopper bolt. It only moves vertically a tiny amount in either direction, so how are spiral witness marks being created?

I have mused about the possibility of the spirals being witness marks from the manufacturing/machining process but I haven't seen enough of them to be able to have a feel for that. You would no doubt have a better idea.

I have also mused about the possibility that these spirals are created when the stopper bolt is screwed in or out, as that at least introduces rotation to cause a spiral. I have no way to evaluate this short of replacing the bracket and monitoring/experimenting with that idea however, and I am not buying a new bracket just for that purpose.

So I am hoping that you, or John, or someone else can provide that missing piece of information that I obviously am not seeing that will give me that eureka moment.

 

[Igofar]

Still thinking everyone is over thinking this.
When the brake caliper or SMC is not working correctly, it can cause this damage.
If the caliper pistons are dirty or sticking and not coming out smoothly and correctly, the caliper does not sit square, and floats on the guide pins.
When the brakes are either applied or dragging, that alone would cause the stopper plug to hit a different spot inside the bracket every time.
Kind of like chatter bumps on a dirt road caused by suspension timing.
I often find witness marks on the plug that indicate that the caliper is not sitting square.
Damaged or failing SMC’s will cause witness marks on the plug in different areas, like on the end on one side, and the middle on the other, pretty obvious signs.

 

[Andrew Shadow]

I would never imply that you could not see if your bike has brake issues, and no disrespect was directed or thrown your way.
I am sorry if you feel so.
I would love to see three photos of your rear caliper and pads (rear/left side/right backside) showing detail of the front pad retaining clip.
You could have damage and not even know it.
I would also like to see your SMC piston movement as well.
Not pressing on it under pressure, but with the PCV bleeder open, and then manually pressing the piston In the bore.
If your piston goes in about 1/2 of an inch smoothly, then returns on its own, I will agree the bore is free and not obstructed.
If the piston does not do that, your function test is deceiving you.
Also, remove the rear brake line and see if it is jammed with jelled up crap.
In simple terms, think of it this way, the lower bout on your guitar has a crack you just found, and it never seems to get worse, it does not sound any different, so you just keep playing.
Nothing wrong with that if that is what you choose to do, but does that mean it is not damaged?

Unfortunately I am 5 or 6,000 miles away from home right now so I can't do any of that. One thing I can answer about is the movement of the SMC piston. Whenever I clean my pistons I move the rear piston out by pumping the SMC to force the piston out. This allows me to check out the SMC at full range of motion at the same time. The SMC piston moves freely in the bore and I have not seen any evidence of binding. Once everything has been cleaned and reassembled the SMC passes the functional test. So far, it still seems to work properly.

 

[Al Gully]

As everyone is throwing their thoughts into the bucket, here is one that I think that is happening.
The axial runout of the rear brake rotor may be causing this orbital pattern in the bore. Was the wheel hub machined flat where they mounted the rear rotor, was there a burr left on there contributing to a wobble or axial runout.
Is it truly perpendicular to the axle bore.
Maybe a different machinist, had a different set up than the previous guy.
I just sent my parts bike rear rim out to a guy on here as still have the bracket on there. I’ll check that bracket as I checked the rear rim for radial and axial runout and it was damn near perfect. Just have to find my readings I took.
When you apply the brakes, the caliper is hugging the rotor that may have a wobble in it. This could causing the wear pattern that we are seeing.
Yes some are worse than others, bad machinist, bad…
Or maybe these parts are made on a CNC machine that is weathered from making millions of parts on it.

 

[Igofar]

I only find these flutes on these brackets that have loose fitting forward pad retaining clips.
I wonder if when the clips are loose, and the pads get tilted, and the torque and weight of the bikes braking force can somehow flex or twist the soft aluminum bracket after it has been heated up by dragging brakes?

 

[Andrew Shadow]

I would never imply that you could not see if your bike has brake issues, and no disrespect was directed or thrown your way.
I am sorry if you feel so.

I took no offense, and intended none. I only wrote that to preclude us from accepting the possibility of incompetence being the root of this problem and then not considering other possibilities. It's all good