Irresolvable rear brake drag? *SOLVED with pics*

Re: Irresolvable rear brake drag?

Scooter said:

Interesting. Just for clarification, when you say that you compressed the left caliper to the fork do you actually mean that you were engaging the pushrod on the Secondary Master Cylinder? A picture would be nice...

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I didn't take any pictures but yes that is what I did.
When you think about the brake bleeding procedure nothing actually compresses that 3rd master. The prop valve gets bleed from the rear brake lever but never gets bled from the front end.
Tilting the SMC up doesn't really accomplish anything if the piston isn't compressed in that master cylinder.

Re: Irresolvable rear brake drag?

okmurdog said:

It sounds as though you have modified your brake bleeding sequence similar to my modification (summary below). My reasoning and observations can be found here.

Brake Lever

1. Left Outer (upper) bleed valve.
2. Right Outer (upper) bleed valve.

Brake Pedal

1. Remove and tilt left front caliper 15 degrees (wood shims inserted between the pads will keep the pads from extending while~if pedal is pumped)
2. Proportioning Control bleed valve. While the SMC (front left caliper) is removed and tilted, manually pump the SMC piston one stroke inward and hold, and have a buddy pump the rear brake pedal to continue bleeding from the proportioning control valve bleeder, which simultaneously re-extends the SMC to the fully out position. Repeat the sequence as necessary.
3. Rear Brake Center bleed valve.
4. Right Front Center bleed valve.
5. Left Front Center bleed valve.
6. Rear Outer (forward) bleed valve.

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Yes, I wish I would have seen this procedure a year ago.

Re: Irresolvable rear brake drag?

If it works for you then do this but there is nothing to be gained by compressing the SMC during the bleed. The obvious reason to tilt the SMC up is that places the outlet above the inlet and it is difficult to push bubbles downhill in a bore of much greater diameter than the inlet/outlet holes.

Re: Irresolvable rear brake drag?

dduelin said:

If it works for you then do this but there is nothing to be gained by compressing the SMC during the bleed. The obvious reason to tilt the SMC up is that places the outlet above the inlet and it is difficult to push bubbles downhill in a bore of much greater diameter than the inlet/outlet holes.

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IMO, I do believe there is something to gain by compressing the SMC - if nothing else, it exercises the piston and cylinder of the SMC the full travel, which I don't believe is accomplished while in use. Additionally, the first time I employed this technique, there was an air bubble that evacuated at the PCV. During the prior two brake bleeds - I had tilted the SMC as instructed in the manual.

Therefore, I'm not totally convinced that exercising the SMC does not have an added benefit, especially if you are bleeding the brakes by 'pushing' fluid through the lines (using the brake levers) versus 'pulling' (employing a vacuum based bleed). Oh, and the convention of the arrows in the service manual could raise some questions regarding the intent - I've sometimes wondered if there is anything the manual that was misinterpreted when it was originally transcribed to English from the Japanese engineers...

Re: Irresolvable rear brake drag?

Compressing the SMC pushes fluid up to the front side of the prop valve. But you're probably right, no reason to do that.
It was this one simple feat that finally solved my rear brake drag and a spongy rear pedal.

Re: Irresolvable rear brake drag?

Pressing the brake pedal with the PCV bleeder open does the same thing Jack. In 10 or 12 bleeds I've not yet had a problem getting air out of the system. But do what works best for you.

Re: Irresolvable rear brake drag?

I use my Motion Pro Bleeder

Re: Irresolvable rear brake drag?

Well,
after going through everything with Igofar I decided to give it a one more try with everything. Thank you Larry!!! Started with cleaning the rear caliper and changing seals. Then, I blew air through all the hoses in the system. When putting everything together I greased it all (pins, etc.) according to the great forum here. Bleeding the system took close to hour and a half. That PCV takes forever and I went through 600ml of break fluid (almost 3/4 of a quart). Is that normal BTW?

Result? I went from 1/4 of a rotation (after a firm foot push) to 1 and 1/4 rotations - which most ST owners consider as a "well working rear break". I dont think it is the best but it will do for now. For the time being I am happy and I will watch the pad wear closely. The bike breaks better so there are some improvements. I think my problem was running non OEM pads a year back and I got some break dust onto the pistons and inside the caliper resulting in dragging pistons. OEM pads sound quieter as well.

Thank you all for great info and help. Gallery of the job here: https://picasaweb.google.com/110251680189521618615/STRearBreakRebuild?authkey=Gv1sRgCMi4xYDmmLi8rgE#

Re: Irresolvable rear brake drag?

Milo, so glad to hear you finally solve your brake problems! Good Job! I repaired two more Frozen rear brakes and SMC this weekend for other members. Same thing, Poor bleed on PCV and bone dry needle bearings in the left caliper pivot pin! I'm starting to believe that these dry needle bearings and galded bushing are most of the problems with the rear break dragging (as well as poor bleeding procedure).
I'm very proud of you! You never gave up....Only wish you lived on my side of the pond so we could ride together!
Igofar-Larry

Re: Irresolvable rear brake drag?

This morning I did my 20-mile commute and after I put the bike on a centerstand I got 3 REVOLUTIONS!!!! Pads are seated and it is getting better. I am so so so happy. And I cant believe I changed everything in the system before going through the caliper!!!!!!!

I cant even express how happy I am!!!!

Igofar said:

Milo, so glad to hear you finally solve your brake problems! Good Job! I repaired two more Frozen rear brakes and SMC this weekend for other members. Same thing, Poor bleed on PCV and bone dry needle bearings in the left caliper pivot pin! I'm starting to believe that these dry needle bearings and galded bushing are most of the problems with the rear break dragging (as well as poor bleeding procedure).
I'm very proud of you! You never gave up....Only wish you lived on my side of the pond so we could ride together!
Igofar-Larry

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Re: Irresolvable rear brake drag?

:bow1::bow1:

rossilvr said:

This morning I did my 20-mile commute and after I put the bike on a centerstand I got 3 REVOLUTIONS!!!! Pads are seated and it is getting better. I am so so so happy. And I cant believe I changed everything in the system before going through the caliper!!!!!!!

I cant even express how happy I am!!!!

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You'll be known from this day forward as the ST Caliper Czech'er! :bow1:
Most of the brake caliper cleaning information is very good. However, people usually just clean what they can see, and not remove the piston's and clean the junk behind them.
Great Job. I'm very happy for you.
Igofar

Re: Irresolvable rear brake drag?

Igofar said:

Only wish you lived on my side of the pond so we could ride together!
Igofar-Larry

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I lived in the US for 10 years (Nebraska ) and toured your piece of asphalt every year on my way to Monterey (US motogp race at Laguna Seca). Califronia is the best place in the world to own a motorcycle I think . Although the Austrian Alps are not bad either - heading there this weekend with my well-breaking Pan European

Re: Irresolvable rear brake drag?

We probably walked by each other several times on Cannery Row after the Moto GP! I'm in monterey about 4 days a week, doing the freediving and scuba diving thing! After a relaxing day of spearing Halibut }<))))> we would walk the Row checking out all the bikes....Ok, I'll admit it, I was peeking into everyone's mastercylinder window and checking the color of their fluid LOL.

I had a problem with dragging rear brakes too. Wore the pads right down, but left the rotor in good shape. Not warped. When I pulled the rear wheel to change tires and brake pads 2 weeks ago, the service guy at a local dealership noticed something odd: A small piece of metal protruding out of the wheel bearing. It was actually part of the wheel bearing on the spline side. He replaced the bearings and also the rubber damper which was showing some wear. Now the rear brake doesn't drag.

I had a wheel bearing go bad in a previous bike, (86 Magna) and ended up having to replace the entire rear wheel because the bad bearing scored out the hub. So glad that didn't happen in this case!

Shout outs for the good service:
Tires- Keel Brothers/Two Brothers Tires. Arrived in 2 days after ordering!
Service- Sparks and Sons Honda, Oblong IL

Re: Irresolvable rear brake drag?

I'm having brake problems on my ST. Any chance you might want to help? I live in Harrah too!

Re: Irresolvable rear brake drag?

john2232 said:

I'm having brake problems on my ST. Any chance you might want to help? I live in Harrah too!

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Absolutely! I'll shoot you a PM.

Right now, I am in the midst of coordinating the annual popcorn fundraiser for our local Cub Scout Pack. Therefore, my time is limited for the next few weekends. Might be able to help during the week.

BTW - glad to have another ST rider in Harrah!

Well done and nice pix