Linked Braking System Confusion

I am searching our site (and any site) looking for ACCURATE detail in how this system actually functions.

This system should be hydraulic only and not require engine running or any particular electrical switching to function. The schematics in the SM under the brake bleeding section is not showing me how it works and I think should. I may be overlooking something there.

It appears that pedal pressure operates the center pistons of all 3 calipers. I have the 3 pistons in the rear caliper pushed in and get no piston action from the bar lever on the outer pistons. This is strange. All info I found says the lever operates the outer pistons up front (4 total) and the center in the rear.
Pedal info is conflicting; some say outer rear pistons in rear and center piston(s) up front; or center pistons on ALL calipers.

My pedal does not operate the outer rear pistons, only the center and probably the front centers. The lever is not operating the rear outer, so what does!

Am I confused, or what?

:?:?:?

The rear outers are actuated by the secondary master cylinder, which you'll find on the left side of the front wheel.

Any time there is braking on the front wheel, the SMC compresses and applies pressure to the rear through the proportional control valve.

--Mark

OK, Mark. I may have this thing figured out.

It appears the pedal operates all 3 center pistons. When the lever is activated, the pressure of the pads on the rotating left front rotor, moves the caliper up/fwd (the bike has to be motion for this rotation to happen), activating the SMC, which applies pressure to the outer rear pistons. This is what had me confused when the bike is static and I was getting no rear outer piston action.

So...........lever action operates ALL outer pistons (6). Pedal action operates ALL center pistons (3). If this is right, everything I've read over the years and now is wrong.

There is something on our forum detailing the linked system, but my password is no longer being recognized. I need to talk to the moderator. I do want to see this.

FYI, Honda has not helped the situation by calling the same systems by two different names (LBS in the USA and DCBS elsewhere), and by revising the system several times over the years. For example, the LBS system on my '93 CBR1000FP is exactly the same as the DCBS systems fitted to ROW-spec bikes of the same vintage, but it is quite different from the LBS system on my '04 ST1300A4...

Ciao,

Here's a version of the diagram in the SM with some color added to make it a bit more clear:


The parts in red get direct pressure from the brake lever. The parts in green get direct pressure from the pedal. Either one causes some amount of front braking, which causes the SMC (yellow) to compress, sending pressure to the outer pistons on the rear.

ST13Fred said:

It appears the pedal operates all 3 center pistons. When the lever is activated, the pressure of the pads on the rotating left front rotor, moves the caliper up/fwd (the bike has to be motion for this rotation to happen), activating the SMC, which applies pressure to the outer rear pistons. This is what had me confused when the bike is static and I was getting no rear outer piston action.

Click to expand...

Correct all the way around.

So...........lever action operates ALL outer pistons (6). Pedal action operates ALL center pistons (3). If this is right, everything I've read over the years and now is wrong.

Click to expand...

Mostly. Pedal action operates all three center pistons directly. Because the front centers cause some braking being applied to the front wheel, the SMC compresses and operates the outers on the rear as well.

--Mark

I thought I read somewhere that the foot pedal operated the two outer pistons of the rear caliper and that SMC affected the center one? The center pistons still being activated at the front as shown. I think this is true in at least one of Honda's linked brake configurations and I thought for the ST.

On my ST adding rear braking after already braking with the front only seems to add a lot more rear stopping power than I would expect from only adding that one extra piston to the mix back there?

wjbertrand said:

I thought I read somewhere that the foot pedal operated the two outer pistons of the rear caliper and that SMC affected the center one? The center pistons still being activated at the front as shown. I think this is true in at least one of Honda's linked brake configurations and I thought for the ST.

On my ST adding rear braking after already braking with the front only seems to add a lot more rear stopping power than I would expect from only adding that one extra piston to the mix back there?

Click to expand...

I'm pretty sure that's the case with the wing... the two rear outer pistons were activated via the pedal.. Pretty sure the ST is the same.

Blrfl said:

Here's a version of the diagram in the SM with some color added to make it a bit more clear:


The parts in red get direct pressure from the brake lever. The parts in green get direct pressure from the pedal. Either one causes some amount of front braking, which causes the SMC (yellow) to compress, sending pressure to the outer pistons on the rear.


--Mark

Click to expand...

Thanks Mark-color coding vastly improves the understandability of the gray/black diagram in the SM!

Blrfl said:

Mostly. Because the front centers cause some braking being applied to the front wheel, the SMC compresses and operates the outers on the rear as well.

--Mark

Click to expand...

AH HA!!!! You're right. The pedal should be applying more rear braking as all 3 pistons eventually come into play. I'm glad I fully understand this now.

Bottom line.............this cats' got some killer brakes.........especially w/ABS.

Mellow said:

the two rear outer pistons were activated via the pedal.. Pretty sure the ST is the same.

Click to expand...

Mostly.

The rear center is activated DIRECTLY via the pedal and the rear outers are activated INDIRECTLY via the pedal that is activating the SMC, by the DIRECT activation of the front left center piston !!!!!! Now talk about a confusing statement!!

You are right; but my point is they are not activated directly via the pedal; but activated, nonetheless.

I'm still confused, so help me out here: Why, and when, would I want to actuate my front brake with the foot pedal? Let's assume my right hand is working as it should.

I can think of when I would NOT want to actuate the front, like during slow tight turns in the mall garage with its greasy concrete. This is a usual situation.

Maybe I rely too much on my rear brake to help me negotiate Boston's tight spaces at slow speeds without tipping over. That link diagram makes me nervous - is the system (or Honda) smart enough to know that I really don't want front brake during slow tight turns?

Bbob


http://microphonium.blogspot.com

I wouldn't be nervous. Many people when they look at these diagrams immediately get some wrong ideas about what actual goes on. The amount of braking applied to the front when you're pressing the brake pedal is minimal. I believe a tech told me that it only applies about 5-10% of what you're applying to the rear. Fairly unlikely that it would put the bike down any different than a regular set up would on similar conditions. Similar arguments and concerns are made regarding the ABS systems as well.

Bbob said:

I'm still confused, so help me out here: Why, and when, would I want to actuate my front brake with the foot pedal? Let's assume my right hand is working as it should.

I can think of when I would NOT want to actuate the front, like during slow tight turns in the mall garage with its greasy concrete. This is a usual situation.

Maybe I rely too much on my rear brake to help me negotiate Boston's tight spaces at slow speeds without tipping over. That link diagram makes me nervous - is the system (or Honda) smart enough to know that I really don't want front brake during slow tight turns?

Bbob


http://microphonium.blogspot.com

Click to expand...

That was a fast response! Thanks.

I like the idea that the proportional valve only provides 10%, and wonder where the tech got that info. Honda ought to describe the proportionment scheme as a transfer function of force in/out per circuit unless there are computers that modify that for speed. Perhaps there are.

Not sure how this concern applies to ABS arguments though - I'm just talking about maintaining balance in dicey slow situations and very tight spaces where control of power to the rear wheel requires rear brake, clutch and throttle together for precise control. Boston is a wicked place to ride, but fun.

Bbob

The system works extremely well in this dicey slow situation. Most of the braking is on the rear, there is not enough force on the front to lock the wheel and cause problems. As you note, ABS is irrelevant in this scenario.

Bbob said:

That was a fast response! Thanks.

I like the idea that the proportional valve only provides 10%, and wonder where the tech got that info. Honda ought to describe the proportionment scheme as a transfer function of force in/out per circuit unless there are computers that modify that for speed. Perhaps there are.

Not sure how this concern applies to ABS arguments though - I'm just talking about maintaining balance in dicey slow situations and very tight spaces where control of power to the rear wheel requires rear brake, clutch and throttle together for precise control. Boston is a wicked place to ride, but fun.

Bbob

Click to expand...

Most dealers send their techs to update seminars every year where they get the info on new models and features. I assume that's where the tech got the info. As far as Honda describing the system better, you have to remember they are dealing with the general populace. Many of them wouldn't understand the systems. The last thing you need as a manufacturer is a confused customer so you keep it as simple as possible. Whereas many of the members on this board have gone through the effort to educate themselves, as a motorcycle service writer, I can testify to the fact that (imho) the average rider has enough trouble just understanding some of the basics. With one customer I spent close to 30 minutes trying to explain how the clutch worked. Another customer I spent an hour trying to explain his charging system and what was wrong with it. He said I was full of crap and just throwing random jargon at him. Unfortunately, this is pretty common.

In regards to the ABS, sorry. What I meant in thought, poorly translated in text. Please ignore it.

Bbob said:

Honda ought to describe the proportionment scheme as a transfer function of force in/out per circuit...

Click to expand...

If they put something like that in the owner's manual, I think all hell would break loose.

...unless there are computers that modify that for speed.

Click to expand...

Nope. It's a 100% hydraulic system.

Not sure how this concern applies to ABS arguments though...

Click to expand...

It doesn't. ABS doesn't come into play until you lock a wheel and, if I remember correctly, doesn't activate below 5 MPH. The LBS otherwise behaves identically on both versions of the bike.

--Mark

Clutches and charging systems are just gimmicks and BS so you can charge more!

I spent days explaining to a microphone customer why his "vocals" sounded so awful in his recording. He doesn't read this forum.

Thanks for the info - very helpful. After a careful look at the service manuals, I think I've got it. Very clever. Can't wait to cruise the Boston Common garage on a wet day.

Bbob


http://microphonium.blogspot.com

So..if I read correctly, it is ok that when I applied the front brake while the bike was on the double stand in my garage, the rear wheel spun freely. This is because the bike was not moving and not because some portion of the system decided to quit...right?

PeteK said:

So..if I read correctly, it is ok that when I applied the front brake while the bike was on the double stand in my garage, the rear wheel spun freely. This is because the bike was not moving and not because some portion of the system decided to quit...right?

Click to expand...

Correct. The front wheel must be turning in order for the secondary master cylinder on the left fork leg to be activated. With the bike on the center stand you can check the operation of the SMC by putting the bike in gear and letting the rear wheel spin with the engine idling. Carefully pull the left front caliper assembly toward the fork (i.e. forward and upward) and note that the rear wheel and engine should begin to slow down.