Another rear brake thread.....sorry

[stevie16v]

I picked up a 2002 st1300 a few days ago.
It has a brake fault and came with a load of new parts.
In a nutshell, the rear brake is dragging, quite a bit but no seized on. I've been through the usual
Bleeding
Rebuild SMC
Bleeding
Tested the smc on the floor, it has minimal free play and activates the rear brake and releases OK.
Calliper strip and clean
Bleeding
Genuine and non genuine rear pads
Removing the tension spring (to test only)
Greasing all the relevant points
Undo the rear end and put back together.

Still, 2 days on I can't get the brake to release properly.

What I have noticed -
When Bleeding the rear most nipple of the rear calliper, fluid doesn't seem to flow as free, I assume this could be down to the PCV

When pushing the middle piston back, it returns no bother.
If I push either outer piston, it pushes out the opposing one, if I try doing them both together, I can't do it by hand.
if i push it back, using a tool, the wheel will turn freely until i apply the brake again

My feeling is that there is some sort of obstruction between the PCV (which bleeds freely) and the rear calliper connection.

Can someone keep me right?

Thank you

 

[jfheath]

It sounds from what you say that there is a blockage in the SMC due to neglect. I cannot say this for certain, but it is extremely likely - the bike is 22 years old and if it hasn't had 22 annual services of the brake system then ..... Well - I'll put it this way. If I was buying a 2002 ST1300, I would buy a brand new SMC for it at the same time. Actually, correct that - if I was buying any second hand ST1300 I would buy a new SMC.

But it could also be due to poor front wheel install, binding calipers, too much grease, badly installed brake pads and springs.
Or all of the above.

Bleeding the brakes will not cure a sticking rear brake. It will release the pressure - but only until you press the pedal again.

Here is how to find out whether the SMC is part of the problem.

When the bike is stationary in your garage, the rear outer pistons are activated by fluid from the rear pedal passing through these components in this sequence.

Pedal -> Front left centre piston - SMC - PCV bleed valve - Rear Outer Pistons.

Pushing in the rear outer pistons is more difficult - the fluid has more components to pass through - including three extremely tiny compenation ports. Nevertheless, they should push in It is possible that the return (compensation) port in the SMC is blocked - either by crud in the very tiny hole, or because a corroded bore is preventing the piston in the SMC from returning properly - blocking the tiny port.

If you open the PCV valve and pistons push in OK, then that last part of the sequence PCV bleed valve - Rear Outer Pistons is clear. Close the PCV valve.
If you push in the front left centre piston without difficulty - then the first part of the sequence Pedal -> Front left centre piston is clear.
If you open up the bleed valve for the front left centre piston (lower valve) and try to push in the rear outer pistons - and that remains impossible - then the SMC is the issue.

When pushing in the rear outer piston - put something in place to stop one of them moving out, and press the other outer piston using two thumbs, on opposite sides of the psiton - if you pres son just one side, the psiton could rock and get jammed in the bore.

You need some reference material:

Search results for query: Brake Maintenance | ST-Owners.com

 

[Buckeyechris]

... Rebuild SMC

@stevie16v

Welcome to the club!

Very few (i.e., almost none) have had much long-term success rebuilding the SMC, including myself. Replacement is the best and safest solution. Sadly, it is also the most expensive solution, and it is a PITA getting all the air out of the rear brake system aftward. Nevertheless, it is well worth it. @jfheath 's diagnostic suggestions are spot on.

Chris

 

[stevie16v]

Thanks for your comments.
Quick update,
I can safely rule out all the components behind the rear calliper eg smc etc, I rigged up a master cylinder directly on to the calliper, it is still dragging. So, the problem is related to something either on/in the calliper or the attaching brackets.
The centre piston feels a bit tighter so I've ordered new seals to be on the safe side and at least rule it out.
Having had a second look at the pads, I'm no longer convinced they are genuine so I'm going to order new ones, although the main places I'd use don't have them in stock!

 

[Josh_ST]

The one I ordered to replace my SMC is sitting right beside me, just have to find time to do bike maintenance It only took a week or so to arrive, huge savings from buying it locally! $93 vs. $188+ (At least in the US)

HONDA OEM Motorcycle parts : BRACKET SUB-ASSY.， L. FR. 06454-MCS-R02 [06454MCSR02]

 

[SMSW]

The centre piston feels a bit tighter so I've ordered new seals to be on the safe side and at least rule it out.
Having had a second look at the pads, I'm no longer convinced they are genuine so I'm going to order new ones, although the main places I'd use don't have them in stock!

IIRC, EBC pads tend to be a bit tight, but some folks here have fitted them with no problems. That said, if you can push the caliper pistons in (all of them), refit the pads and if the wheel spins freely before you hit the brake lever(s) (either of them) then the problem is not the pads. This of course, assumes the pads fit the caliper properly.

The O-rings inside the caliper are square in cross section. When you hit the brakes, the pistons are forced outward against the pad. This distorts the cross section of the O-ring. Release the brake and the O-ring goes back to square, pulling the piston back into the caliper a few thous of an inch. Dirt, corrosion and age can prevent the retraction. Replacing the rubber ring and going over the caliper is not a bad idea.

My description nonwithstanding, from John's post, your problem is probably in the SMC.

Keep us posted what you finally figure out.

 

[jfheath]

I can safely rule out all the components behind the rear calliper eg smc etc, I rigged up a master cylinder directly on to the calliper, it is still dragging. So, the problem is related to something either on/in the calliper or the attaching brackets.

I disagree! You may have found that the caliper is dragging all by itself - which is a good catch. But it doesn't rule out the possibility of other parts causing it to drag as well.

In your first post, you said that both outer pistons pushed in easily - while pushing the other outer piston out. It suggests that isn't the cause of the caliper sticking.

With the caliper and pads still in place check the position of the pad retaining clip - viewed through the wheel from the right hand side.



Above is a photo of my previous 1300. It is the rear caliper viewed from the right hand side through the back wheel. Note the area outlined in red. The chrome retaining clip has a tag that is bent around the caliper bracket , and it has a raised rectangle area in the alloy casting.

See how far down that chrome bit is in relation tot he small raised rectangle in alloy the casting? It should be roughly central. Note the gap above the tab end of the brake pad. There should be no gap. The brake pad is securely located in the chrome retaining clip.

The chrome retaining clip is not located securely in the caliper bracket - it is slowly burrowing its way to freedom - grinding away the lower part of the alloy recess. The position of that chrome tab on the raised alloy casting acts like a wear gauge. It shows how far out of line this pad is. Typically, the wear is significantly more on this side, than it is on the other - and that difference can make the caliper sit at an angle on the bracket.

This wear seems to go hand in glove with the sprial patterns found in the stopper bolt hole. And together they seem to accompany rear brake dragging problems. Not always - but I have read about it on here enough times to associate the combination of symptoms.

Since you are quite happy rigging up the hydraulics - next time you have the brake lines off - take the caliper and the bracket off. Then :

• Check the large oval hole in the caliper bracket - for the stopper bolt. Note if there is any spiral rifling marks - 'James Bond' looking down the barrel of a gun pattern.
• Clean up (do not remove or undo) both slider pins - one on the caliper, one on the bracket.
  Remove the boots and clean them out. The pins should be nice and shiny.
• Put the caliper back on the bracket. The caliper should move easily in and out on those slider pins once the boots have been fitted and a thins mear of rubber or silicone grease applies. Any binding suggests that they are not parallel.
• Check the pad spring in the roof. See the article and photos in 'avoiding the pitfalls' (link above). It is possible for it to have a small locating tag bent or for it to be fitted in the wrong way round.

(I've made a few edits to correct typos and to make it a bit easier to read)

[edit - additional info]
Peter sent me a PM about my advice to not undo the slider pins. It is not a hard and fast rule. It is a rule that I made up and one which I follow, and which I recommend. My reasons:

1) It is not necessary to remove them unless they need replacing.

2) Quite a few problems on here have been caused by the slider pin being out of alignment (ie cross threaded).

3) There is a massive - no, scrub that - there is an absolutely ginormous error in the official Honda Workshop manual ie my legit UK 2003/4 manual and the 2003 version widely available on line. Maybe others too, I don't know. It labels the torque setting for that main slider pin incorrectly at 69Nm. (End of section 17 Hydraulic Brake in my Manual)

The actual torque for that pin is 27Nm. The people who annotated the diagram have quoted the torque that is required for the caliper bracket stopper bolt. I don't know what torque is required to strip the threads from the caliper alloy, but I reckon that it would not be much shy of 69Nm.

 

[stevie16v]

So, after quite a bit of fault finding.....turns out the caliper was sitting at a very slight angle. Had a look at the caliper and could see it wasnt quite right in where the 14mm bolt /pin sits. I managed to lay hands on a carrier from someone nearby.....job done!

I think it may have been someone has fitted the caliper bolt after the rear wheel has been torqued, damaging the keep for the calliper bolt.

 

[Hornet]

I picked up a 2002 st1300 a few days ago.
It has a brake fault and came with a load of new parts.
In a nutshell, the rear brake is dragging, quite a bit but no seized on. I've been through the usual
Bleeding
Rebuild SMC
Bleeding
Tested the smc on the floor, it has minimal free play and activates the rear brake and releases OK.
Calliper strip and clean
Bleeding
Genuine and non genuine rear pads
Removing the tension spring (to test only)
Greasing all the relevant points
Undo the rear end and put back together.

Still, 2 days on I can't get the brake to release properly.

What I have noticed -
When Bleeding the rear most nipple of the rear calliper, fluid doesn't seem to flow as free, I assume this could be down to the PCV

When pushing the middle piston back, it returns no bother.
If I push either outer piston, it pushes out the opposing one, if I try doing them both together, I can't do it by hand.
if i push it back, using a tool, the wheel will turn freely until i apply the brake again

My feeling is that there is some sort of obstruction between the PCV (which bleeds freely) and the rear calliper connection.

Can someone keep me right?

Thank you

Ok, I have an '06 ST1300 with 57,000 miles on it. After a recent ride I noticed the rear brake was dragging. Wheel turning very stiff and rotor was hot! My experience kicked in..I was a Technician/Service manager at a Honda dealership from 1979-2021. The primary culprit for rear brake drag in the Honda linked braking system is the secondary master cylinder ( SMC). In fact the same system is on the GL1800 and I can't tell you how many SMC recalls kits I installed on the GL1800 for the same issue. The Secondary master cylinder is activated every time you apply the brakes,front or rear. With that said it gets a work out! I replaced mine and brakes are now operating normal. A very simple test is while the bike is on its center stand just push the SMC on the left caliper very hard a couple of times. Then check the rear wheel to see if the rear brake is dragging. If the rear wheel drags the SMC is the culprit. Save yourself some time and money and replace the SMC. You'll notice the part number has superseded as well. Hopefully this helps.

 

[jfheath]

This has been a recurring topic on these pages - and we keep repeating the same message to people who experience rear wheel drag - although it isn't always the answer.

Its good to know that there are Service Managers out there that know about this - how to detect it and how to fix it, because the experience reflected in many posts convey a very different picture.

What I could never understand was why the Goldwing had recalls to rectify the problem but the ST1300 and the VFRs never did.

 

[stevie16v]

With myself it absolutely 100% was not the smc, I even put that in but was still getting messages telling me it was, it couldn't have been though because I set up a standalone master cylinder to test the rear in isolation.
My issue was down to a damaged caliper carrier where it appears someone has removed the caliper bolt then tightened up after the rear wheel spindle etc had already been tightened up. This resulted in the caliper sitting slightly off. It's been replaced now and has been fine since

 

[jfheath]

Good feedback. There are plenty of people who will shout "SMC", when there are so many other possibilities. Your issue being one of them. It often results on a spiral wear pattern in the hole for the stopper bolt. Think James Bond opening sequence gun barrel. The Odds are in favour of the SMC as it is the main victim of neglect. But Hamfisted reassembly must run it pretty close. In both cases I am tempted to look at the colour of the brake fluid.

Me - I have a 100% failure rate with the re-application of silicone grease to the caliper slider pins. ie it happened just the once when my rear brake got very hot following a test ride after reassembly. I didn't have time to fix anything before setting off after the next day - but I had just serviced everything - wheel off, calipers off, complete flush etc etc It had to be something that I had done. A long night, I took everything off again that was wheel, brake related. I found nothing - except I had packed the slider pins with silicone grease.

Result - air lock - which acted like a spring pushing the pads onto the disc surface.

 

[MidLife]

What I could never understand was why the Goldwing had recalls to rectify the problem but the ST1300 and the VFRs never did.

Easy to understand.

Most on this site do not consider it to be a technical shortcoming, but a maintenance issue! Why should Honda bother?

For Honda to move, you have to put pressure on them. Starting by reporting the instances, not just here, but to the NHTSA for us in the US.

How many have ever reported our ST SMC incidents to the NHTSA: you can go and check the database, only an infinitesimal small fraction of what is constantly been reported here. Why should Honda bother??

The GL people fought for it and got results (long battle though, as it took 5 years and three notices for Honda to finally get to the bottom of it).

@Hornet can probably tell you, but once Honda finally got cornered, they had to get very serious about it.

In the heat of it, if you ever called their California Tech Center, they had a dedicated line just for the GL SMC case.

I had an electrical issue once on a trip late in the day and called the nearest dealership after hours, hoping for an appointment the next day. They dispatched a tech to meet me at the shop and fixed the problem right then. How was it possible? They had a tech on call 24/7 dedicated to the GL SMC swap, ready to help any GL day or night in this popular touring area. They cordially dispatched this guy to help with my touring bike. I indirectly benefited from the GL SMC debacle.

There are of course other reasons Honda moved on the GL but not on the ST (one of them being GL is a much larger and menacing and revenue generating crowd than we are) , but don't expect them to come and knock at your door and ask if there is anything they can do for you. They won't!

 

[Hornet]

Just a follow up on my '06 ST with the rear brake drag issue. I purchased the bike used when it was Ten years old. So, I have no idea about the maintenance that was done. But, I have changed the brake fluid every Two years since the purchase back in 2016. (bike had 34K on it then,57k now). As stated earlier I was employed at a Honda dealer from 1979-2021. Number ONE cause of rear brake drag withe the linked brake system is the secondary master cylinder. Sure, there could be other causes as well. But, The SMC must be checked first. A very simple test for this. With bike on center stand just spin the rear wheel. Wheel should spin freely, and you'll most certainly will hear the noise of the pads. Now, push really hard on the SMC,many times too. If the rear wheel now is stiff to turn immediately push hard on the REAR brake pedal. If this frees up the rear wheel you have a malfunctioning SMC. What's happening in this scenario when the REAR brake is applied the brake fluid pressure at the SMC forces the piston backs to its full rest position. Now,look at the photos of my old SMC. The 1st photo you can see the corrosion at the area where the SMC rod contacts the piston. In the second photo I pushed piston down with a screwdriver and its stuck. At one point or another moisture made its way in even though the rod boot is in excellent shape. In all the years of working in a Honda service department, I don't recall seeing this issue on an ST1300. Or even VFR800's,VTX1800's,etc. Now,Gold wings? Yes. But there are way more GL's out there then ST's,not even close. GL riders tend to rack up more mileage too. You know these ST's are getting old. But they are wonderful sport touring bikes even to this day. Here is what I recommend. For sure change the brake fluid at least every two years. I would also perform the SMC test I described. And perform an inspection of the SMC. Very carefully retract that boot and look for signs of corrosion. If SMC passes test and no corrosion your good. But, if it fails replace the SMC assembly. Yes, they're expensive. And yes,you can rebuild it. But you don't mess around with brakes. That's the old service manager in me preaching now. I also own a 05' ST1300 with 110k on it. It passes the test, but I haven't retracted the SMC boot and inspected. I'll pour another cup of coffee here soon and take a look. How I found the issue on my '06 was after a 125 mile ride with my wife on the back ! When we arrived home, and she hopped off the bike in the garage I noticed the bike was hard to roll. Pretty scary quite frankly. Potential for a massive rear brake failure. Again, hopefully this clears the air about this rear brake issue.

 

[MidLife]

As stated earlier I was employed at a Honda dealer from 1979-2021. Number ONE cause of rear brake drag withe the linked brake system is the secondary master cylinder.

One dealer in town used to have an Octopus like hose assembly they were connecting to several bleed ports at the same time on the ST for flushing (similar to what is found on Auto Flush Machines). I couldn't figure out if it was their own contraption or if it was an official Honda shop accessory.

Did you have a similar procedure for the ST or were you going by the book?

 

[Hornet]

We used a vacuum pump operated by compressed air in our service department. Honda did not have an official shop accessory you mentioned. And the sequence of bleeding was by the book in reference to the bleed ports. Final stages were bled manually. Now that I'm retired, I performed the brake repair in my garage. I simply manually flushed and bled the brake fluid. This can be a little tricky to do by yourself, but I did it. The key bleed port for the rear brakes on the ST1300 is located on the RH upper frame member by the ignition coil. So, this requires the RH fairing to be removed. When removing the secondary master cylinder air will enter that line. This is the brake line that goes from the SMC to the rear brake.

 

[Fawlty]

The key bleed port for the rear brakes on the ST1300 is located on the RH upper frame member by the ignition coil. So, this requires the RH fairing to be removed. When removing the secondary master cylinder air will enter that line. This is the brake line that goes from the SMC to the rear brake.

You can get to that bleed port without removing the RH fairing. It's a bit tight, but with a little manipulation it can be done.