The dreaded SMC and rear dragging brake question

[Sadlsor]

While somewhat finicky, I do like the behavior of my brakes when properly bled.
Been a while, so they are due again, and I can feel the almost mushy difference.
One thing to note about front- only, or rear- only braking is this (taught in MSF beginner classes)...
Whatever you do on a daily basis, and the routine / habit you develop, will be what happens nearly every time you face an emergency situation. Because in a panic situation, we reflexively revert to habit. That's why elite police and military train and train and train for emergency situations.
So if you're accustomed to only using the front brake and that time comes when you face that "Oh $h!t" moment, you're tossing away the other 30% of stopping power from the rear, and that might be all you need to make the difference between hitting the obstacle or stopping in time to avoid it.

 

[macclan5]

that explanation really does make perfect sense! there comes a point where frustration (going to sell this #@$@ bike) morphs into determination (going to fix this #@$@ bike). really close the latter. more to follow

 

[macclan5]

You're description is close to the process. I recommend the following sequence/steps.

Remove the the SMC/Caliper and tilt it at least 15 degrees. If you have a car jack stand, the bottom of the SMC brackets will fit on the stand between eyelets.

1. Pound on the rear brake pedal a few times, then hold it down.
2. Next open the PCV bleed nipple and fluid will start to come out. Be sure to close the bleed screw before the pedal bottoms out and before you release it.
3. At this point, start tapping on the SMC and surrounding lines (I used the handle of a small hammer).
4. Then, push the plunger in on the SMC all the way. The first time you do this, you're unlikely to encounter much resistance.
5. Next, repeat steps 1 and 2, followed by step number 4. The second time you will likely feel some resistance.
6. Again, repeat steps 1 and 2, followed by step 4. The third time, you will experience a good deal of resistance.
7. Continue to repeat steps 1 and 2 until you no longer get any air bubbles.

As you noted, keep an eye on the fluid level in the rear reservoir. Then you complete the rest of the bleed sequence. If you don't reinstall the SMC/Caliper to the fork, be sure to place a shim the same thickness of your rotor between the pads. If you are not certain of the remaining bleed sequence (there are four more steps), please let me known.

At this stage, recommend that the you weight down the brake pedal and tie the brake lever as close to your grip as possible. Leave it overnight. In the morning, release the lever and pedal. Test both, and if you feel any sponginess, follow the bleed sequence from start to finish again. NOTE: overnight, any remaining air will migrate to the calipers just behind the pistons. Doing a final bleed, following the sequence, should rid your brake circuits of the remaining air.

If you're thinking this is a lot of work to get the air out of your brake lines, you're right. It's just one of eccentricities exhibited by the ST13. It also requires you to devote at least double the amount of time you think it will take to complete the bleed sequence. Others recommend to allot a full two days for the entire process. If it takes less time, you are doing extremely well.

just in from the garage...

SMC is solid...really no give to it when trying to compress it by hand.

Not seeing any bubbles when bleeding any other valve/brake. Rear pedal is firm. Front brake firm but not as much as rear. Have put pressure on rear pedal and front brake lever. Pistons in left front and rear caliper fully retracted. Will repeat process this evening.

 

[jfheath]

Just in case there was a misunderstanding, my post above (#9) was not describing the sequence for bleeding the brakes. It was trying to find out where the blockage is (if there is a blockage). The fluid from the rear master cylinder travels to each of those places in that order - FLC, PCV, RO.

You should be able to feel some movement at the SMC, but not much more than a mm. The important thing being that it should apply the rear brakes. And the more important thing being that it should release the rear brake when you let go of the SMC.

 

[Catmandu2]

SMC is solid...really no give to it when trying to compress it by hand.

So if what you are describing is a smc that has no give to it (and therefore,, it does not brake the rear wheel by hand activation),, then it is seizing,, and should be replaced (not rebuilt). If that is the case,, it will lock up on you for sure,, and the bike should not be ridden in this condition. Maybe it has already done this too you ?? Anyway,, certainly don't risk others safety for the sake of a reasonably inexpensive component,,, that needs to be replaced anyway,,, cheers,, CAt'

 

[The Dark Shadow]

Reading this, and finding out that a new SMC unit costs $360 Canadian, I am filled with even more anxiety and stress than before...

My dream bike, and I can't get the brakes working right...

Sheesh... $2000 bucks or more trying to sort out my poor fuel economy issues, and I still haven't got my brakes fixed. And people say BMW's are expensive to maintain... :-(

I think the moral of this story is: Don't let engineers design things without integrated collaboration with users and repairmen...

 

[Andrew Shadow]

I think the moral of this story is: Don't let engineers design things without integrated collaboration with users and repairmen...

In all fairness to those engineers, based on your posts in your threads my impression is that you are the unfortunate victim of incompetence. Much of what you have spent to date seems to have been due to misdiagnosis and/or incompetence on the part of the people who have been working on your motorcycle for you. That is not something that can be blamed on the motorcycle or its designers. As I have posted before, I am not there so I can't do any of the tests to verify so I can't state with certainty that your problem is the SMC. However, if a defective SMC does turn out to be the source of all the problems that you are experiencing, this should have been diagnosed and repaired from the very beginning. If a defective SMC is the end result, the only repair that you would have needed to pay for is the SMC repair. You would not have spent all the rest of the money that you have spent not fixing the original problem.

It is unfortunate that you did not find a competent shop from the get go. This would have led to a quicker and cheaper repair and a lot less frustration for you.

 

[MidLife]

SMC is solid...really no give to it when trying to compress it by hand.

Are you really saying you cannot push it in at all by hand?

Or just saying it is now firmer with no free play anymore? When pushing on it holding the caliper, feel should be close to what you feel when activating the brake lever or pushing on the rear pedal by hand.

A master cylinder is a master cylinder, secondary or not. Its piston has to move in for brake activation.

 

[jfheath]

Reading this, and finding out that a new SMC unit costs $360 Canadian, I am filled with even more anxiety and stress than before...

My dream bike, and I can't get the brakes working right...

Sheesh... $2000 bucks or more trying to sort out my poor fuel economy issues, and I still haven't got my brakes fixed. And people say BMW's are expensive to maintain... :-(

I think the moral of this story is: Don't let engineers design things without integrated collaboration with users and repairmen...

Hmmm. I would suggest a completely different moral.

The standard / Abs bike has not been in production for nearly 10 years. The second hand ones are getting old. Even when they were brand new, there were enough service centres where members on here have commented that they did not know:

• how these brakes worked;
• that front wheel correct installation procedure and sequence is critical;
• that it matters which wheel bearing you install first;
• That Moly 60 for rear splines was never replaced with an alternative by Honda;
• that front wheels have 42psi, not 36;
• that non-OEM pads can screw your brake system
• That fairing bolts have different shoulder lengths for a reason
• That hydraulic fluid has to be replaced every 18 months, even if the bike has never been used

You don't have to have the skills to service your bike, but you do need to know what to expect from your service centre so that you can help them to get it right, and know when they are talking balderdash.

 

[Gus1300]

When pushing on it holding the caliper, feel should be close to what you feel when activating the brake lever or pushing on the rear pedal by hand.

Yikes! If that's the case, I have some work to do...my lever and pedal move MUCH more than the SMC does. [edit: I misunderstood the above comment - caliper movement, not lever or pedal]

I have an SMC on the shelf just in case mine goes bad (I don't think it is yet as it does still pass the 'engage and release' test when kicking the rear tire with my foot and activating by hand.)

 

[Buckeyechris]

just in from the garage...

SMC is solid...really no give to it when trying to compress it by hand.

Not seeing any bubbles when bleeding any other valve/brake. Rear pedal is firm. Front brake firm but not as much as rear. Have put pressure on rear pedal and front brake lever. Pistons in left front and rear caliper fully retracted. Will repeat process this evening.

@macclan5,

Now my inquiring mind wants to know if your rear brakes are dragging now that you've bled the system? After rebuilding the rear caliper, replacing the subassembly/mounting bracket, spring pad, boots, and pads the best I could manage was still 1.5 revolutions. Larry (Igofar) suggested I take it out for a short test ride, since the pads and other items were so new. After a 5 min. ride, I returned to the garage, put my bike on the center stand, and spun the rear wheel, lo and behold the rear wheel spun 5 revolutions.

 

[Buckeyechris]

Reading this, and finding out that a new SMC unit costs $360 Canadian, I am filled with even more anxiety and stress than before...

My dream bike, and I can't get the brakes working right...

Sheesh... $2000 bucks or more trying to sort out my poor fuel economy issues, and I still haven't got my brakes fixed. And people say BMW's are expensive to maintain... :-(

I think the moral of this story is: Don't let engineers design things without integrated collaboration with users and repairmen...

@The Dark Shadow,

That's nearly $264 USD! Outrageous. I can get a SMC unit here in the States for $146 plus shipping from Ron Ayers.

Sorry to hear that you're having troubles, but @jfheath is correct that the civilian models have been out of production for over a decade. Few Honda techs really know much about this bike, which is why I tend to work the bike myself.

Nevertheless, a failing/failed SMC is a major safety issue. Before I replaced my SMC recently, I had rebuilt it approx. 2 years ago. It was still "working" to a degree because it would stop the rear wheel from turning when squeezed against the fork. However, the internal spring would not return it to the proper position. Thus, it was sticking in the bore. I knew there was a problem when the SMC would rattle and clank as I moved the outlet hose.

When working properly, the plunger on the SMC should only move 1 mm or so to active the inner and outer pistons on the rear caliper. Although dragging rear brakes can be caused by other issues (e.g., too much grease on the slider pins or bent slider pins, etc.), a failed or failing SMC is near the top of possible causes.

I would suggested that you find someone on the Canadian RAN list who is willing to help you sort through your concerns.

 

[MidLife]

Yikes! If that's the case, I have some work to do...my lever and pedal move MUCH more than the SMC does.

I have an SMC on the shelf just in case mine goes bad (I don't think it is yet as it does still pass the 'engage and release' test when kicking the rear tire with my foot and activating by hand.)

This is about the motion of the pistons of the different Master Cylinders, not the motion of the hand lever of foot pedal itself.

 

[MidLife]

@The Dark Shadow,

When working properly, the plunger on the SMC should only move 1 mm or so ...

Looks like there is a lot of work still required for bleeding mine!

Travel is 3-4 mm for me right now, in line with hand brake piston travel and what can be seen here it would appear:

 

[macclan5]

Finally sharing an update...been off the bike/not made the time to wrap it up.. Very fortunate to get through to Larry (Igofar) on the white courtesy phone (which now has live acoustical guitar music while u wait) couple days ago, whom walked me successfully through the process, despite my best efforts. My commute to work is 50 miles one way and today was first time riding since Larry guided me through the process. Guessing it will take couple hundred miles for the new brake pads to properly seat, back tire spins more freely (2 complete revolutions), rear disk is almost cool to the touch like front disks, fuel economy seems better judged by the instant mpg display and bike rolls backwards much easier when in neutral. Best of all, slightest pull on the front brake level and the bike slows down like a tractor beam from the Enterprise just locked on. BIG SHOUT OUT to Larry. Few know this bike as well as him and even fewer can give directions over the phone on how to troubleshoot such a finicky system. To all who shared their ideas and suggestions--thank you as well. It confirmed others have wrestled with this system and found success

 

[Buckeyechris]

Thanks for the update @macclan5. It sounds like you've made progress. I'm also glad you had the opportunity to be tutored by THE ST-Whisperer! Isn't it a great feeling of self accomplishment?!!!!

 

[Obo]

I've read a few folks who stated they developed SMC issues after doing fork seals.

I can't help but wonder if moving all those lines somehow results in debris in the brake fluid (that hasn't been changed regularly) in moving and finally clogging up the SMC filter / small ports, proprtion valve etc.

 

[Fawlty]

I've read a few folks who stated they developed SMC issues after doing fork seals.

I can't help but wonder if moving all those lines somehow results in debris in the brake fluid (that hasn't been changed regularly) in moving and finally clogging up the SMC filter / small ports, proprtion valve etc.

Good point Obo. You may well be correct there.