2006 ST1300 ABS 46k odo Rear Brake locks up

[1fixitman]

I have been a member of this forum for a while and have not posted much. I have learned a lot by reading a lot of the brake post and many other post here.
My rear brake locks up when I press medium pressure on the rear brake every time. In short the bike was stored outside always under a cover for four years and driven very little. Then Stored inside a storage unit for two years. Took it out for a spin and rear brake locked up and the heat ruptured one of the rear hoses.
I ordered rear seals, rear stock brakes and new hoses. Put everything together, bled all the brakes at all points front and rear in the proper order. Rear still locks up. I read a lot on the site about front brakes and SMC.
At this point I took both front brakes and SMC apart. Had difficult time removing pistons from left and right front cylinders. I ordered new seal kits, brake pads, SMC rebuild and new pistons(old ones damaged so bad removing had to order new pistons).
All the bores on all calipers(front and rear) and the SMC were smooth and clean prior to installing new seals and pistons. THE REAR PISTONS WERE NOT REPLACED but were NOT CORRODED or pitted.
I cleaned and rebuilt the front brakes and SMC with all new stock parts and bled all brakes front and rear following proper order.
Rear brake locks up with light to medium pressure on the rear pedal. Wheel will not move. The rear rotor was damaged during the first brake incident and I cleaned up the rotor with light sanding even on each side while bike in first gear on center stand. IF I VENT THE REAR CYLINDER THE PRESSURE WILL RELEASE and the wheel is free again.
I am asking for help. I can only imagine that the only thing left is the Rear Master Cylinder needs a rebuild??
I am an accomplished electrician and mechanic starting in the US Navy for 12 years and 11 years as a multiskilled technician in a Bridgestone/Firestone tire factory. I drive Commercial trucks now. I really do not want to pay the stealership to do the repair when I have come so far. I need some help from those of you who have solved this issue for folks in the past. I want to spend money in the right place on this repair. Thank you.

 

[Igofar]

Private Message Sent, awaiting reply.

 

[kenG]

could be a flexy.
my old st1100 done in the rear flexi and it was 28yrs old, grabbed and wouldnt release properly to i loosened the bleeder. the hose was making itself a one way valve whatever way the inside gave up.
sounds like it could be either. cheapest option first.


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[1fixitman]

Info sent to Igofar. KenG I replaced both rear hoses from the initial meltdown/lockup. Thank both for replies so soon.

 

[kenG]

there is a valve at the front left disc, there is another under the right panel at the edge of the tank, you may go down the line one by one to the master cylinder. no point replacing it if its something else. with your mechanicing knowledge, im sure youll find it.

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[heffly]

Time to go through all components in the system IMHO. Clean, rebuild, replace as needed. If one neglect failure has occurred there are potential other IMHO.

 

[CruSTy]

I reccomend the IGOFAR Treatment. Larry is the best option for sorting this out. Please PM IGOFAR.

 

[Kevcules]

This is a 2006 ST1300......It does sound like a weakened flex hose, but you changed them. If it was the SMC , you would think the problem would happen only when you activated the "front" brake lever.
Larry is definitely a good resource to help you, as well as lots of members here. Just make sure your side conversation makes it back here for us to benefit in the answer to your problems.

Good luck....

 

[fnmag]

This is a 2006 ST1300......It does sound like a weakened flex hose, but you changed them. If it was the SMC , you would think the problem would happen only when you activated the "front" brake lever.
Larry is definitely a good resource to help you, as well as lots of members here. Just make sure your side conversation makes it back here for us to benefit in the answer to your problems.

Goof luck....

Keep us updated as to the problem and solution.

 

[1fixitman]

Today I loosened the nut on the rear wheel. Then removed the 14mm bolt on the rear caliper. I cleaned the new grease off of the slider pin/bolt and ensured no corrosion on the pin and applied a thin coat of grease. Torqued the 14mm bolt to spec and then tightened the rear axle nut to spec. I vented both rear caliper bleeders and verified the caliper moved left and right on the slider pins without binding. I pressed the front brake. No issues. I pressed the rear brake to extend the pistons in the caliper and still have rear wheel lockup after the brakes engage the rotor. The only way I can get the rear wheel to unlock is to bleed pressure from the rear caliper bleeder. The brakes are stock/brand new and have not bedded in yet. I am waiting on a tool from Amazon that Igofar had me order. It is Motion Pro 08-0143 brake bleeder. It should be here by March 5th end of day. I will keep everyone posted as I work thru this issue.

 

[BakerBoy]

The SMC on the left front fork seems likely the culprit.

 

[kenG]

vacuum?? type.?
i got a new air bleeder, bled it through quite successfully on friday, havent been out to test it yet. weather isnt for my fairy ass, too wet, too cold. lol.
but if a brake is still gripping the rotor, im not sure how? its fluid pushed against the piston under pressure,
* all a bleeder machine will do is dispel air.
*all opening a bleeder valve is doing is releasing the pressure!

**something isnt releasing.

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[kenG]

The SMC on the left front fork seems likely the culprit.

take the calliper off and clamp a couple of old pads in it to keep the pistons back, then try your rear wheel brake test again.

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[1fixitman]

In my OP I stated that I rebuilt the SMC, front pistons, front seals, rear seals and both rear hoses. I did not measure the inside diameter of the SMC bore to check for out of round as Igofar asked me on the phone. I did replace all rubber boots but did not say in OP. I will remove rear brake tomorrow and place a stack of razor utility blades in the area where the rotor is supposed to go to keep the pads from collapsing too far. As good as shims and I have a bunch of blades. I have nothing going on so I have time to burn. We will see if the brakes lock up on the razor blades as well. I don't know what releases the pressure after I let go of the pedal but I will check the results and post back tomorrow.

 

[kenG]

in simple terms, when you release the pedal, the valve in the master cylinder comes back far enough to clear the line and releases pressure,, which is why i would check each joint along the line to eliminate each pressure point.
as for what releases the pressure, in a working system without fault, it is the seal that withdraws the brakes. they simply pucker out like an anus. then pull the piston back the tiniest amount to release grip, and be ready for the next brake action.
which is why they look square unlike a hub seal.
have you checked the valve beside the tank? you have to remove the right cowl/fairing to get at it.

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[BakerBoy]

Symptoms are of a stuck SMC. You can test it as follows: bike on center stand in neutral engine off, while manually rotating rear wheel, rotate SMC [left front disc brake] forward and see that the rear wheel stops. Let go of the SMC and see that you can again freely rotate rear wheel.

 

[Igofar]

It looks like Larry was waiting for you to post something. He'll sort you out.

But just for information for the board - something that I have not seen mentioned much about the SMC on the 1100. There is a linkage behind the left hand grey cowl which is worth investigating. It is a casting with 3 holes and there is a metal plate on each side. One of the 3 holes connects to the bottom end of the SMC push rod. The other two have needle roller bearings, bushes and dust seals and these connect to the fork leg and caliper bracket. The idea is that when the front brake is applied, the caliper pivots and the movement of that linkage activates the SMC.

It is hidden away behind the grey plastic shroud, and can be left forgotten and slowly seize up. When they are seized, there is plenty of force available to shift them to apply the rear brake, but there is not enough force available to allow the return of the SMC plunger - which should happen easily when it is all clean and free to move.

View attachment 236567


I'm not saying this is the answer to your problem - there are plenty of other possibilities which Larry will tell you about. I have not seen this particular item on the 1100 system mentioned much.

Go get yourself some Hot tea or coffee John....he has an 06 ST1300

This is a 2006 ST1300......It does sound like a weakened flex hose, but you changed them. If it was the SMC , you would think the problem would happen only when you activated the "front" brake lever.
Larry is definitely a good resource to help you, as well as lots of members here. Just make sure your side conversation makes it back here for us to benefit in the answer to your problems.

Good luck....

Now think about what you just wrote..."only when you activated the front brake lever"...remember when you press the foot pedal, it activates the center piston on the left front caliper, and when it grabs....you guessed it, it activates the SMC etc.
Thanks for all help and suggestions that ya'll are providing to our member in need

The SMC on the left front fork seems likely the culprit.

I agree, that it may be the SMC, however, he stated that he only activated the rear pedal to move the pistons when it locked back up, the SMC would not have been activated unless the bike was in motion.
I'm thinking bent clip tabs, suction on the guide dowels, or a bent rear caliper bracket, among other things....
Don't fret fixitman, you'll have plenty of assistance from all these kind folks, we'll crack this nut and get your bike sorted for ya.

In my OP I stated that I rebuilt the SMC, front pistons, front seals, rear seals and both rear hoses. I did not measure the inside diameter of the SMC bore to check for out of round as Igofar asked me on the phone. I did replace all rubber boots but did not say in OP. I will remove rear brake tomorrow and place a stack of razor utility blades in the area where the rotor is supposed to go to keep the pads from collapsing too far. As good as shims and I have a bunch of blades. I have nothing going on so I have time to burn. We will see if the brakes lock up on the razor blades as well. I don't know what releases the pressure after I let go of the pedal but I will check the results and post back tomorrow.

Just thinking outside the box here...I've been known to do that once in a while...when we talked, you said you could hardly turn your rear wheel?
Did you do the function test, and if so, what happened? Did it release the rear wheel?
Call me tomorrow before you dive into the bike again, as I have a few more questions.
Before you start tearing the rear wheel apart, and removing it from the bike, pull the hanger pin, grasp the ends of both pads with your thumb and index finger, and while squeezing the pads against the rotor, turn the wheel backwards, this will simply allow both the pads to ride out with ease.
Once the pads for out of the caliper, and while the housing is still attached via the 14 mm head stopper bolt, and the axle, try and turn the wheel now.
It should be completely free to spin, and you should get several rotations with one brisk spin.
If not....I'm wondering if your bike has a couple different things going on at the same time.
I'm curious if your flange bearings are toast?
One more thing to rule out.
Talk to you tomorrow.
Larry

 

[kenG]

i dont know why you keep opening the bleeder to release the brake. you need to loosen it back up the line to fine the fault point.


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[kenG]

Doh !
Coffee taken as prescribed. I have some brilliant answers over here. Just waiting for the right question to be asked.

Where did that come from ? I was sure I read ST1100AY ? Anyone have a spare brain for a 1954 Male ? This one is well past its best.

the title !! [emoji1787][emoji1787][emoji1787][emoji1787]

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[CYYJ]

I will remove rear brake tomorrow and place a stack of razor utility blades in the area where the rotor is supposed to go to keep the pads from collapsing too far.

Just a thought for you: I went to Home Depot's lumber section and picked a cut-off piece of 1/4 inch particle board scrap out of the bin next to the table saw... then asked them to cut it into 3 pieces about 4" by 6" - that worked great for keeping the pistons from falling out when the caliper assembly was removed from the disc. Cost nothing, and is a bit safer than razor blades.

Mind you, it is more difficult to commit suicide with the blocks of particle boards after you spend several hours trying to fix the brakes and have no success...

Michael