brake problem HELP!
Seasoned HDF Member
Joined: Dec 2010
Posts: 6,848
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From: Florida
Check offset and make sure you bleed it right. The first time I had a four piston I opened both blessed bolts on both sides of the caliper. Bleed the one furthest away then close it and do the other side
Road Master
Joined: Apr 2009
Posts: 1,205
Likes: 3
From: Mebane, NC
OP, in your second post you said that it's like you are still applying the brakes. This is a Master Cylinder problem. Even if the pistons in the Caliper are sticking, the worst problem you will have will be some excess drag and maybe a bit of noise after you release the brake as the Brake Pads are still dragging on the Rotor face. But it will NOT be like you are still squeezing the Brake Lever.
By any chance was the Master Cylinder or the Brake Lever worked on; either before you replaced the Caliper, or when the work on the Caliper was being done?
When the Brake Lever is released, a Brake Master Cylinder has a passage that opens the brake line to the Brake Fluid Reservoir. This passage is called the Compensator Port. The Compensator Port allows the Brake Fluid that was pumped into the Brake circuit when the brakes were applied, to be released. It also allows Brake Fluid pressure to return to zero in a Disk Brake System. When you squeeze the Brake Lever, the first few thousandths of an inch that the master Cylinder Piston moves, closes off the Compensator Port. As the Brake Lever is moved further the Brakes are applied because the Brake Fluid is now trapped between the Master Cylinder and the back sides of the Caliper Pistons. The Caliper Pistons then push the pads against the rotor. If the Master Cylinder is not fully releasing, and it doesn't have to be by much (we're talking thousandths of an inch here), once you apply the brakes you'll either be waiting a very long long time for the pressure to drop (if ever) or you'll have to open the bleeder screw or crack a line to release the pressure. If this is what is happening on your bike; once you apply the brakes . . . they will be APPLIED! You may be able to pump the Lever once or twice more and make the problem even worse, but the brakes probably will not release until you open the bleeder screw or crack a line as mentioned earlier. There should be just the slightest amount of movement in the Brake Lever before it starts pushing the Piston Cap and it in turn starts pushing the Master Cylinder Piston Assembly.
The three illustrations that I've attached show a Master Cylinder with the Brakes Released, Brakes Applied, and one with the problem you are having.
An easy way to see if the Compensator Port is being uncovered as it should be, is to: 1.) Remove the Master Cylinder Cover, 2.) Apply the Brakes, 3.) Release the Brake Lever, 4.) Observe the master Cylinder Reservoir. 5.) If the Compensating Port is being uncovered as it should be, you should see a small spurt of fluid returning to the Fluid Reservoir when you release the Brake Lever. If not . . . that's your problem!
By any chance was the Master Cylinder or the Brake Lever worked on; either before you replaced the Caliper, or when the work on the Caliper was being done?
When the Brake Lever is released, a Brake Master Cylinder has a passage that opens the brake line to the Brake Fluid Reservoir. This passage is called the Compensator Port. The Compensator Port allows the Brake Fluid that was pumped into the Brake circuit when the brakes were applied, to be released. It also allows Brake Fluid pressure to return to zero in a Disk Brake System. When you squeeze the Brake Lever, the first few thousandths of an inch that the master Cylinder Piston moves, closes off the Compensator Port. As the Brake Lever is moved further the Brakes are applied because the Brake Fluid is now trapped between the Master Cylinder and the back sides of the Caliper Pistons. The Caliper Pistons then push the pads against the rotor. If the Master Cylinder is not fully releasing, and it doesn't have to be by much (we're talking thousandths of an inch here), once you apply the brakes you'll either be waiting a very long long time for the pressure to drop (if ever) or you'll have to open the bleeder screw or crack a line to release the pressure. If this is what is happening on your bike; once you apply the brakes . . . they will be APPLIED! You may be able to pump the Lever once or twice more and make the problem even worse, but the brakes probably will not release until you open the bleeder screw or crack a line as mentioned earlier. There should be just the slightest amount of movement in the Brake Lever before it starts pushing the Piston Cap and it in turn starts pushing the Master Cylinder Piston Assembly.
The three illustrations that I've attached show a Master Cylinder with the Brakes Released, Brakes Applied, and one with the problem you are having.
An easy way to see if the Compensator Port is being uncovered as it should be, is to: 1.) Remove the Master Cylinder Cover, 2.) Apply the Brakes, 3.) Release the Brake Lever, 4.) Observe the master Cylinder Reservoir. 5.) If the Compensating Port is being uncovered as it should be, you should see a small spurt of fluid returning to the Fluid Reservoir when you release the Brake Lever. If not . . . that's your problem!
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Tourer
Joined: Dec 2005
Posts: 370
Likes: 7
Well found a great deal on a chrome master cylinder, had that installed and the problem went away. Which leads me to believe it was a bleed problem. Now I have a new problem. I have to squeeze the hell out of the front brake to get the light to come on. how do I fix? thanks
May our Moderator Rest in Peace
Joined: Sep 2006
Posts: 11,386
Likes: 35
From: Rochester, NY
Sounds like you may have installed the handle improperly and accidentally broken the switches plunger or forgot the flat copper spring that holds the microswitch in place.
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