Linked Brakes - Apologies

Maersk · Nov 2, 2016

Hi. New member. Have an issue with the linked brakes. Have read through many of the previous posts, but can't quite find one that matches my symptoms. Apologies for adding another thread. It's unlikely I will be able to fix this myself but am hoping if I list my symptoms I'll at least be able to get diagnostic feedback so I can go to the dealer armed with a plan that avoids them troubleshooting for several days. That's my hope anyway. Thanks, in advance, for any counsel.

Front brake lever has no impact in stopping the rear wheel.
Using the foot brake binds the 3 rear pistons
Manually separating the rear pistons from the brake pads (so the rear wheel will spin) and using the front brake lever only causes the SMC to swing forward an inch or so and makes a clunk as it reaches it's stop.
Rear pistons are shiny clean (DOT4)
Brake and clutch fluids have recently been replaced (after the binding started)
2007 ST (non-ABS) with 14k miles.
Flower Mound, Texas

My sense is this is a bad SMC that needs to be replaced, but would be delighted to hear there is a silver bullet trick! Thanks, in advance.

Igofar · Nov 2, 2016

PM me a contact number and I will call you on the white courtesy phone and explain how to solve your brake issues.
Igofar

W0QNX · Nov 2, 2016

Igofar said:
PM me a contact number and I will call you on the white courtesy phone and explain how to solve your brake issues.
Igofar

Wouldn't it be better "for the forum" if you posted directions here?

I'd like to know the answer myself.

With all your experience you should have some typed up and saved notes you could use to copy and paste sometimes.

Igofar · Nov 2, 2016

Due to recent hand surgery (both hands) I am unable to type for more than a couple minutes, and have to use two fingers to do so.
I have been trying to help folks on the phone till I can type again.
I would be glad to call you as well if you wish.
Larry

wjbertrand · Nov 2, 2016

Maersk said:
Hi. New member. Have an issue with the linked brakes. Have read through many of the previous posts, but can't quite find one that matches my symptoms. Apologies for adding another thread. It's unlikely I will be able to fix this myself but am hoping if I list my symptoms I'll at least be able to get diagnostic feedback so I can go to the dealer armed with a plan that avoids them troubleshooting for several days. That's my hope anyway. Thanks, in advance, for any counsel.

Front brake lever has no impact in stopping the rear wheel.

Using the foot brake binds the 3 rear pistons

Manually separating the rear pistons from the brake pads (so the rear wheel will spin) and using the front brake lever only causes the SMC to swing forward an inch or so and makes a clunk as it reaches it's stop.

Rear pistons are shiny clean (DOT4)

Brake and clutch fluids have recently been replaced (after the binding started)

2007 ST (non-ABS) with 14k miles.

Flower Mound, Texas

My sense is this is a bad SMC that needs to be replaced, but would be delighted to hear there is a silver bullet trick! Thanks, in advance.

How is the SMC swinging forward? Is the bike in motion when you are doing this test?

Igofar · Nov 3, 2016

Fluids have not been changed in many years....
When performing the smc test, the unit does not stop or slow down the rear wheel - failed test.
I believe the rocking forward mentioned was when pushed forward during the test, it moved a lot, then would fall back - failing test etc.
MP tool to be ordered as well as a new SMC and washers.
We now need to help convince him that he can repair this himself as good, or better than the stealer.....with our help.

dduelin · Nov 3, 2016

wjbertrand said:
How is the SMC swinging forward? Is the bike in motion when you are doing this test?

The SMC movement is in the range of 2-5 mm failed or good. I thought the same as Jeff when reading. An inch measured how and where?

Brakes are a critical system and some knowledge and self confidence in one's abilities is necessary.

Anna'sDad · Nov 3, 2016

Here are my thoughts on your brake situation.

Maersk said:
Front brake lever has no impact in stopping the rear wheel.

This suggests that the SMC (Secondary Master Cylinder), located at the left-side front brake caliper, is not functioning properly.

Maersk said:
Using the foot brake binds the 3 rear pistons

A failed SMC can prevent brake fluid from returning to the rear (pedal) master cylinder, thus the two outer pistons of the rear brake caliper will not release.
If the center piston of the rear brake caliper is also not releasing, this could indicate a problem with either the rear brake caliper, or the rear master cylinder.
This earlier post may be of assistance in determining which brake circuit of the rear brake caliper is not releasing.

Maersk said:
Manually separating the rear pistons from the brake pads (so the rear wheel will spin) and using the front brake lever only causes the SMC to swing forward an inch or so and makes a clunk as it reaches it's stop.

This type of movement of the SMC indicates that the mechanics of the SMC appear to be functioning properly, however the distance of travel, as well as the noise of the SMC indicates the SMC piston is probably "bottomed out" at the end of the SMC cylinder bore.

Maersk said:
Rear pistons are shiny clean (DOT4)

Okay, this helps in diagnosing the situation of "If the center piston of the rear brake caliper is also not releasing".

Maersk said:
Brake and clutch fluids have recently been replaced (after the binding started)

Good start to ST1300 brake maintenance.

Maersk said:
2007 ST (non-ABS) with 14k miles.

Not particularly relevant, I rebuilt the SMC (first time) on my '06 ST1300 at 8,622 miles.

Maersk said:
Flower Mound, Texas

Get much rain in Flower Mound? Water ingress to the SMC seems to be the greatest determining factor as to when a failure of the SMC can occur.
This sketch made be of assistance in understanding how a stuck piston in the SMC can cause the rear brakes to not release.

Lastly, this is a sketch of the Linked Brake System for the ST1300, that may be of assistance.

Anna'sDad · Nov 3, 2016

Igofar said:
We now need to help convince him that he can repair this himself as good, or better than the stealer.....with our help.

Two things jumped out at me when I read this comment:

I have no means to evaluate the ability, or quality of the poster's mechanical/hydraulic acumen. Much less determine if these abilities are equal or better than the Honda mechanics.
I think it a disservice to generalize Dealer Service as "stealers". This suggests a negativity toward vehicle dealers to anyone reading the statement, perhaps leading them to make poor choices when maintaining their vehicle.

Please note, while I am comfortable rebuilding my brake system (or yours for that matter), and I am willing to assist others with a similar ability in doing so, I would be very uncomfortable trying to "convince" another of unknown abilities that performing critical system maintenance is within their means.

T_C · Nov 3, 2016

Anna'sDad said:
Maersk said:

Front brake lever has no impact in stopping the rear wheel.

Click to expand...

This suggests that the SMC (Secondary Master Cylinder), located at the left-side front brake caliper, is not functioning properly.

Forgive me for being cinfused, nothing new.

But I though the front brake lever and it's associated fluid had nothing to do with the rear brake. Isn't that what the SMC is for, driving the rear brakes once the front brake lever causes the front brakes to activate.

If he is testing this while the bike is in the garage, wheels in the air, the front brake lever would not stop the rear wheel unless someone is spinning both tires simultaneously. No?

PS I realize I could see this on the diagram you drew & referenced, but I can't access google docs while in the cave.

Igofar · Nov 3, 2016

Anna'sDad said:
Two things jumped out at me when I read this comment:

I have no means to evaluate the ability, or quality of the poster's mechanical/hydraulic acumen. Much less determine if these abilities are equal or better than the Honda mechanics.

I think it a disservice to generalize Dealer Service as "stealers". This suggests a negativity toward vehicle dealers to anyone reading the statement, perhaps leading them to make poor choices when maintaining their vehicle.

Please note, while I am comfortable rebuilding my brake system (or yours for that matter), and I am willing to assist others with a similar ability in doing so, I would be very uncomfortable trying to "convince" another of unknown abilities that performing critical system maintenance is within their means.

Ok, I would have to agree with both of your comments.
What I should have said is that perhaps with the help of other forum members, (local tech event) near him, he would be able to find assistance from folks like yourself, who have the knowledge and experience in dealing with this type of service etc.
I didn't mean to imply that a person without proper skills, tools, and knowledge, attempt to work on something as serious as the brake system without assistance.
Thank you for pointing out my misleading comments.

wjbertrand · Nov 3, 2016

T_C said:
Forgive me for being cinfused, nothing new.

But I though the front brake lever and it's associated fluid had nothing to do with the rear brake. Isn't that what the SMC is for, driving the rear brakes once the front brake lever causes the front brakes to activate.

If he is testing this while the bike is in the garage, wheels in the air, the front brake lever would not stop the rear wheel unless someone is spinning both tires simultaneously. No?

PS I realize I could see this on the diagram you drew & referenced, but I can't access google docs while in the cave.

These are my questions too.

Anna'sDad · Nov 4, 2016

T_C said:
If he is testing this while the bike is in the garage, wheels in the air, the front brake lever would not stop the rear wheel unless someone is spinning both tires simultaneously. No?

Hmm... Absolutely correct, for the SMC to function, rotational energy from the front wheel must be transferred to the SMC, thus the pivoting left front brake caliper assembly.

Given the scarcity of detail in the thread starter's list of statements, I assumed the statement Front brake lever has no impact in stopping the rear wheel., was an observation made during operation of the motorbike.

What is they say about assuming....

T_C said:
Forgive me for being cinfused, nothing new.

Doesn't seem like you're confused at all about the operation of the SMC!

JimGregory · Nov 4, 2016

I am curious as to how this goes as I have an 07 non abs bike with 14000 miles as well. I also called the bat phone one day and thanks very much to a MOST helpful Igofar! I think it was preventative maintenance on my SMC.

Jethro77 · Nov 4, 2016

I think that just about anyone could do this repair with the assistance of this site and Igofar ... personally I have little mechanical skill but the willingness to try and the perseverance to keep bleeding the system until it's right is what is needed. Doing a repair like this not only saves money but will also build confidence and familiarity with the bike.
OF course the brakes are a vital system and must be properly tested before riding!
The owner should at least try to do the repair themselves if physically able, worst case they end up taking the bike to the dealer to finish the job....

Maersk · Nov 4, 2016

Thanks for all the feedback. Despite my 37 years of riding, this is my first forum and am realizing the downside to not providing clear details. Please find below some clarifications:

(1) To Wjbertrand: the test of the front lever not stopping the rear wheel was executed with the bike on the center stand. I have since learned the bike needs to be in motion for an accurate test. Relative to the SMC swinging forward until it's stop, that test was with the bike in motion. I manually separated the rear pistons from the brake pads and performed a ride using only the front brake. Using the front brake only, the SMC moves about one inch forward, and makes a clunk when it hits it's stop (can move no further forward). Ordinarily when both brakes are being used the SMC will only move 2 to 3 mm.

(2) To Anna'sDad: appreciate the feedback / observations.

Since the initial post, I have been blessed with a chat on the bat phone with the great Igofar. Am ordering a new SMC, a Motion Pro bleeding tool and plan to do some serious research before tackling the project. For the record, Igofar For President!

wjbertrand · Nov 4, 2016

1" inch sounds like way too much movement for the SMC, I don't think mine moves more than 1 cm. Another way to check its function is to put the bike up on the CS, start the engine and put the transmission in first gear so the rear wheel is spinning at idle speed. Then from in front of the motorcycle grab the SMC and pull it forward toward you. Be careful not to pull the bike off of the CS! You should hear the engine slow down slightly as the SMC transfers pressure to the center piston on the rear brake caliper. If you can pull hard enough you can actually stall the engine with this test.

MidLife · Nov 4, 2016

wjbertrand said:
......as the SMC transfers pressure to the center piston on the rear brake caliper.

Just a detail......SMC actually activates the two outers.

Igofar · Nov 4, 2016

Let me get this straight....you want him to start the bike, put it in gear, and while the rear wheel is spinning, trying to rock the bike off the center stand, you want him to get in front of the bike and pull the front end of the bike forward.....towards him.....now that there is funny :rofl1:

Igofar · Nov 4, 2016

MidLife said:
Just a detail......SMC actually activates the two outers.

Linked Brakes - Apologies

Maersk

Igofar

W0QNX

Blacksheep Tribal Member

Igofar

wjbertrand

Ventura Highway

Igofar

dduelin

Tune my heart to sing Thy grace

Anna'sDad

Anna'sDad

T_C

Igofar

wjbertrand

Ventura Highway

Anna'sDad

JimGregory

Jethro77

Maersk

wjbertrand

Ventura Highway

MidLife

Igofar

Igofar