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Discussion Starter · #1 ·
I currently am running Avid Juicy 5 with G2 Cleansweep rotors. I just replaced the front with a G3 and notice there is barely any room between the pads and rotor. Is this because the G3 is new and possibly a hair thicker because it's unused? Is there any way to bridge the gap. I already did the caliper bolt trick. The wheel spins ok, but rubs a little. Also, will this affect the reach of my brake lever. I tried adjusting but noticed that they grab right away and even when I adjust the reach they are still a little touchy. Thanks
 

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Discussion Starter · #3 ·
I can try that...should I use a flathead to push them back? Will i be able to see them scoot back?
 

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im using a g3 clean sweep in the rear with my bb7's. They rub a lot which results in me stopping a lot and adjusting the (red knobs???) a lot. I might go back to the roundagons
 

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mcap said:
I can try that...should I use a flathead to push them back? Will i be able to see them scoot back?
Yes, you can see them move. Yes the new rotor and/or new pads will be thicker and require resetting the caliper pistons.

I would pry them all the way into the caliper to be sure both sides have moved equally. It takes quite a bit of pressure to move them. If you have them fully apart, you will have to pump the lever 2-3 times to move them back out after you have put the wheel back on. This will set the correct gap.
 

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Discussion Starter · #7 ·
Yes, went from 185 to 185mm... figured I would put the G2 on the rear since that has a 160mm currently and the new one up front since it does most of the work. Just waiting for the bracket to arrive for the rear
 

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Discussion Starter · #8 ·
Thanks a lot, I tried it last night and notice only one of the pads moves. I never got the pad to move and stay in a new position though. SHould I hear a click or something or push untill they stay in place against the outer most part of the caliper?
 

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Open the bleed screw with a rag around it to catch fluid. Then push the pistons back into the caliper. Trying to do it with the bleed screw closed is like pushing an elephant up a flight of stairs. That, and every time you manage to push one side in, the fluid pressure in the caliper will just push it right back out again when you pry the other side in. Do it carefully, and you won't need to bleed or add fluid.
 

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gmcttr said:
Strange...I've never had to open the bleed screw to push the pistons fully into the caliper.
Oh, you can do it on some brakes, it's just not easy, and you can damage the piston. Opening the bleed screw enough to release the pressure allows them to slide right back in with little effort.
 

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heff® said:
Open the bleed screw with a rag around it to catch fluid. Then push the pistons back into the caliper. Trying to do it with the bleed screw closed is like pushing an elephant up a flight of stairs. That, and every time you manage to push one side in, the fluid pressure in the caliper will just push it right back out again when you pry the other side in. Do it carefully, and you won't need to bleed or add fluid.
This is bad advice. There is a correct volume of fluid that a brake system should contain. You don't need to let fluid out to reset the pistons; I've worked on tons of different brakes and never needed to do this. If you're careful, it is easy to push the pistons back without damage. Even if you don't introduce air, you will no longer have the correct amount of fluid with your method.

Pretty much every brake that I'm aware of should be filled with the pistons pushed all the way back, so if they have been bled or filled incorrectly you might be able to get away with your method, but that doesn't make it the right way to do it.
 

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eric1115 said:
This is bad advice. There is a correct volume of fluid that a brake system should contain. You don't need to let fluid out to reset the pistons; I've worked on tons of different brakes and never needed to do this. If you're careful, it is easy to push the pistons back without damage. Even if you don't introduce air, you will no longer have the correct amount of fluid with your method.

Pretty much every brake that I'm aware of should be filled with the pistons pushed all the way back, so if they have been bled or filled incorrectly you might be able to get away with your method, but that doesn't make it the right way to do it.
Bad advice unless they are over filled...
 

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PissedOffCil said:
Bad advice unless they are over filled...
If you actually manage to squeeze enough fluid out just releasing a bit of the pressure to make a difference........wow. We're not talking a high-volume system here. Add a couple of drops of fluid (without overfilling) if you think too much came out.

Do it without opening the bleed screw, just be careful. Take the pads out, use a box-end wrench (10mm should fit fine), not a screwdriver. Kindof rock the pistons back in side-to side, don't push directly on the center and pry all at once, you can easily bend the piston.
 

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PissedOffCil said:
Bad advice unless they are over filled...
No. Just bad advice. If they are over filled, you ought to reset the pistons and do a proper bleed to get the correct volume of fluid. Not try to squeeze what you guess is the right amount of fluid out the bleed port in the caliper.

heff® said:
If you actually manage to squeeze enough fluid out just releasing a bit of the pressure to make a difference........wow. We're not talking a high-volume system here. Add a couple of drops of fluid (without overfilling) if you think too much came out.

Do it without opening the bleed screw, just be careful. Take the pads out, use a box-end wrench (10mm should fit fine), not a screwdriver. Kindof rock the pistons back in side-to side, don't push directly on the center and pry all at once, you can easily bend the piston.
There is a pretty fair bit of fluid in the caliper cylinder behind the piston. And as you say, it is not a high volume system. If you open the bleed port, nearly all of the fluid in the cylinder will go out, rather than back up to the reservoir where it belongs. How much is too much? How do you measure how much came out into the rag? How do you put "a few drops" back in?

Do NOT rock the pistons. That is the best way to break them. Slow, steady pressure straight back into the cylinder is the best way to push them back in.
 

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eric1115 said:
No. Just bad advice. If they are over filled, you ought to reset the pistons and do a proper bleed to get the correct volume of fluid. Not try to squeeze what you guess is the right amount of fluid out the bleed port in the caliper.

There is a pretty fair bit of fluid in the caliper cylinder behind the piston. And as you say, it is not a high volume system. If you open the bleed port, nearly all of the fluid in the cylinder will go out, rather than back up to the reservoir where it belongs. How much is too much? How do you measure how much came out into the rag? How do you put "a few drops" back in?

Do NOT rock the pistons. That is the best way to break them. Slow, steady pressure straight back into the cylinder is the best way to push them back in.
Hayes and Hope both tell you specifically in the service manual to rock the piston gently while pressing. We're not talking full arm-wrenching here. Just slightly. Called Avid (actually for an unrelated question) but I asked their tech guy the best way to retract the pistons, particularly if one or both were sticking. His answer...."use a box end wrench, and rock back and forth gently while pushing to help break the piston free. Keep doing that until the piston moves back fairly easily." Asked about opening the bleeder screw. "Yes, if the pistons are requiring too much force to push them back into the caliper, you probably have it overfilled. Loosen the bleed screw a small amount, just to allow excess pressure to blow off, and the pistons will retract easier. Check your fluid level afterwards, but there should be little loss. Close the bleed screw quickly, or you might allow air into the system, requiring a bleed." I can check with Magura, but unless they changed designs, putting the bike in a stand and removing the reservoir top cap was the best, and safest, way to go with manual pad retraction.
 

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This was very helpful. I just swapped my G2 clean sweep for a Ashima and was getting a lot of brake rub. I measured and found the Ashima is .025" thicker than the G2. I was just about to bleed some fluid out and decided to search here first.

Put a flat head screwdriver between the pads and easily opened the gap. Put the wheel back on, pumped the brakes and all is good now. No more brake rub.
 

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If the system is overfilled, it will be impossible to reset the pistons. Or they will creep back out if you do manage to push them all the way back into their bores.

DOT fluid brakes can become overfilled even if they were not to start with. DOT fluid is hygroscopic and will absorb moisture, this will change the fluid volume. This may be fine at first because as the brake pads wear, the pistons pump out more, more fluid occupies the caliper. But when you try to reset the pistons, the fluid is pushed out of the caliper. The reservoir will take up some of the fluid. But if the system is overfilled, the piston will not go all the way back in. If you try to force it, this could cause damage to piston seals, to the MC, to the reservoir bladder/seal, or otherwise cause an external leak.

There is no harm in leveling the lever and opening the bleed port on the lever. Excess fluid will be pushed out. No more. No air will enter, there will be no suction. If air does enter, it's still only in the resi, it will not affect the rest of the system. If you want, you can even do a "mini-bleed" that will take all of 20 seconds to draw any air out of the resi. But I have never found that to be necessary.

I think at one point, Shimano even recommended you level the lever and remove the resi cap when pushing the pistons back into their bores. Can't remember for sure if that was in their tech docs though.
 
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