rear caliper question

Replaced rear pads and now rear brakes are dragging. Tons of threads on this but I have a specific question on how the pistons are suppose to work. I have the wheel off and brake pads off. Figured I would clean the pistons off a little better. BTW, they pressed back into the caliper very hard. I'm sure that means something bad to you technical folks. The brake pedal is moving the outer 2 pistons and I can't get the center piston to move at all. I always understood the brake lever would control the outer 2 and the pedal the center. I know the smc comes into play here somewhere too. I guess my question is, how do I get the center piston out so I can clean it better? I also noted the slider pin was quite dry. Do I have to use the special pin lube or will something else suffice that I might have laying around (little moly 60 maybe?? LOL). I hate working on these things!!!

The SMC activates the center piston,, try pumping it by hand or spin the tire and apply front brake .

v8-7 said:

The SMC activates the center piston,, try pumping it by hand or sin the tire and apply front brake .

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I tried pumping the smc, didn't do anything. Now that you mention it, in the past I have spun the rear wheel with my foot and activated the smc by hand and it stopped the wheel. Hmm, wheel is off now, but it should still move the piston like you say. I'll go try again.

I use axle grease on the sliders, not sure if it is the best , but it works though .
Yes , the pistons are hard to push in as you are forcing brake fluid backwards into the master cylinder .

Spin the front tire and hit the front brake.

So, rear most piston was the only one moving with the pedal, until I held it in place with my thumb. The the forward most piston moved, which makes sense, but the center also moved with the pedal. Not as much, but it did come out. So, now I'm wondering if the outer 2 should move equally? I gotta get this baby freed up...I'm headed your way in a few weeks Stan

BTW, the front lever is doing absolutely nothing to the rear caliper. Is that normal when the bike is stationary?

The front lever activates the front brake, if the front tiire is spinning, it will kick the smc valve which will activate the rear piston.

my number is 831 818 6514 .

There is no direct connection between the front lever and the rear caliper. The action of the LF caliper when it brakes on the LF rotor presses the SMC which applies the center piston in the rear caliper.

v8-7 said:

I use axle grease on the sliders, not sure if it is the best , but it works though.

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If you use any grease at all, silicone only. If petroleum grease gets on the boots or piston seals, it will eat them away.

--Mark

You may have a marginal SMC... just changed on out for another member. If it doesn't depress more than about an 1/8", there may be some corrosion in the bore causing the plunger of the SMC to "stick" and not release the pressure targeting the center piston on the rear caliper, or it also could be the dry hanger pin. Lube with a silicon based grease or a specified "brake component" grease (heat resistant). After you replace the rear wheel, try rotating the front wheel as fast as you can and then apply the front brake... the SMC should compress the rear pads. It may be easier to get a friend to help you with this. To get the rear caliper pistons out further, remove the pads and insert a thinner piece of wood, plastic, or aluminum and depress the pedal, and then activate the SMC... should cause the pistons to move. When off the bike, I use compressed air to extract the pistons.

I appreciate the help trying to figure this out. The wheel was turning pretty freely before the pad change so I'm hoping the SMC is ok. I plan to clean and exercise the Pistons a few more times in addition to lubing the pin and hopefully I will be ok. Sure wish I could run to NAPA and grab a reman caliper for $50 like I do with my 4 wheeled vehicles. Lol

The service manual shows the pad retaining pins installed dry and that's all I've ever done. The pins are exposed to road grit and grease collects crud on the pins then grinding a flat spot. The pins themselves will wear over time even dry, why coat them with grinding paste?

With the new pads in place how easy was it to insert the retaining pin?

Ken, If this can wait till good weather & clear roads? I can make a road trip & bring what is needed?
When is the last X U flushed the brake system? Do u exercise the SMC. Have U separated the calipers? Cleaned & lubed the pins.
U should be able to just push the pistons in with your fingers.
U do have another bike?
later Bob

Hey Bob, I may take you up on that if I can't get it fixed this weekend. Or maybe I can ride to you if I don't touch the rear brake pedal? I'll see how it goes on Sunday and let you know. Thanks Buddy!!

kendoo said:

Or maybe I can ride to you if I don't touch the rear brake pedal?

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This might be dangerous if your rear brake is seizing. Can also damage the rotor with too much heat. Last summer I had to replace my SMC because the rear break was seizing just as you described your's. The rear tire would only spin 1/4 turn with a hard push, normally I got three spins out of it. The rotor was so hot it almost burned my hand with gloves on, I was lucky it wasn't damaged. I got a new SMC with the bracket for about $108 from HandaParts Direct, best prices on new OEM parts I've found.

kendoo said:

Hey Bob, I may take you up on that if I can't get it fixed this weekend. Or maybe I can ride to you if I don't touch the rear brake pedal? I'll see how it goes on Sunday and let you know. Thanks Buddy!!

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Ok, let me know. Sil-gel.

dduelin said:

The service manual shows the pad retaining pins installed dry and that's all I've ever done. The pins are exposed to road grit and grease collects crud on the pins then grinding a flat spot. The pins themselves will wear over time even dry, why coat them with grinding paste?

With the new pads in place how easy was it to insert the retaining pin?

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Dave, the pad pin went in easy and was dry. The slider pin is the one I was concerned with as it was dry and gunked up a bit. I plan to clean and lube that. I ride in all kinds of crap up here and I know its not doing my bike any favors.

Reginald said:

This might be dangerous if your rear brake is seizing. Can also damage the rotor with too much heat. Last summer I had to replace my SMC because the rear break was seizing just as you described your's. The rear tire would only spin 1/4 turn with a hard push, normally I got three spins out of it. The rotor was so hot it almost burned my hand with gloves on, I was lucky it wasn't damaged. I got a new SMC with the bracket for about $108 from HandaParts Direct, best prices on new OEM parts I've found.

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I hear ya. I was thinking if it was the outer pistons that was causing the issue, I might get by with only using the front brakes to ride to Bob's (2hr by interstate) which is what I use most anyway. I know a slight pad drag can cause some serious heat quick.

Bring it on down. Today is not a good day. The sun is out now. But can see the snow shower on the Blue Mountain=North.