rear brake woes - Sportbike Forum: Sportbike Motorcycle Forums
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post #1 of 11 (permalink) Old 12-02-2007, 05:50 AM Thread Starter
 
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rear brake woes

Hey guys, just realized that my rear pads are slightly grabbing the rotor, and i have about 50% of the tension(for lack of a better term) than what I used to have, before the most recent time i changed my tire. Not exactly a "brake guy" I never really had to deal with them apart from minor things. What needs to be done? bleed em and im good? eh?

thanks :cheers
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post #2 of 11 (permalink) Old 12-03-2007, 05:24 AM
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The rotors are to be treated like glass during tire changes so I can only think that something happened to it during the last tire change. Have you measured the rotor for runout? Is it pulsing on use?

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post #3 of 11 (permalink) Old 12-03-2007, 05:53 AM
 
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if you have never adjusted anything on your brakes and you still have good pads it might just need to be adjusted at the lever. im not sure what you mean "its grabbing the rotor" cause thats what the brakes are supposed to do
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post #4 of 11 (permalink) Old 12-03-2007, 12:16 PM
 
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With you bike being 7 years old, this is what's happening -

1) You have a buildup of dirt & corrosion on the caliper piston.

2) When you reinstalled the tire, and 'pumped up' the brake, you drew air into the system because of a low m/c level.

Easy enough to fix.

#1 The accumulation of brake dust and dirt around the exposed circumference of the caliper pistons can cause the brakes to drag. Whenever I change pads, and sometimes more often depending on what I see, I take a toothbrush, cloth, and brake cleaner and remove all dirt from around the pistons. I do this by forcing each piston in turn ALMOST completely out of its cylinder. When you can rotate each piston by hand, it is out far enough. Make sure it is as clean as possible completely around its circumference. If you have never done this before be careful, as it would be easy to injure your fingers, If you go too far and force the piston completely out, it's okay. Just clean it really well and push it back in. Check for
burrs, raised edges or deep indentations on the rod which guides/supports the brake pads. A good cleaning and a few strokes with a points file will take care of the rod.


#2 - You'll want to not just bleed your brake, but actually replace the fluid by bleeding until the fluid coming out is clear & clean.

I expect this will fix your problem. Ask Santa to bring you some new pads....
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post #5 of 11 (permalink) Old 12-06-2007, 07:20 AM Thread Starter
 
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i suspected i just needed to bleed my brakes, but why did you say i need new pads? mine are perfectly fine. almost brand new
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post #6 of 11 (permalink) Old 12-06-2007, 03:33 PM
 
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You don't necessarily need new pads. Just that nothing feels better than new(or almost new) pads, it's winter up there and I figured you weren't in a hurry, and you're going to have to pull the pads to clean the pistons.

If you just bleed the system, it will fix the feel of the brake, but it won't stop the pads from dragging.

+1 on what Kanwisch said. Treat that rotor like it was made of glass. And - treat the pads like you were gonna eat off 'em.
Good luck with it.....
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post #7 of 11 (permalink) Old 12-09-2007, 05:08 PM
 
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what is that thing you speak of???... rer brake? what is it used for? should i look for it on my bike? how is it used? lol.
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post #8 of 11 (permalink) Old 12-12-2007, 11:34 AM
 
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Quote:
Originally posted by Rundog
With you bike being 7 years old, this is what's happening -

1) You have a buildup of dirt & corrosion on the caliper piston.

2) When you reinstalled the tire, and 'pumped up' the brake, you drew air into the system because of a low m/c level.

Easy enough to fix.

#1 The accumulation of brake dust and dirt around the exposed circumference of the caliper pistons can cause the brakes to drag. Whenever I change pads, and sometimes more often depending on what I see, I take a toothbrush, cloth, and brake cleaner and remove all dirt from around the pistons. I do this by forcing each piston in turn ALMOST completely out of its cylinder. When you can rotate each piston by hand, it is out far enough. Make sure it is as clean as possible completely around its circumference. If you have never done this before be careful, as it would be easy to injure your fingers, If you go too far and force the piston completely out, it's okay. Just clean it really well and push it back in. Check for
burrs, raised edges or deep indentations on the rod which guides/supports the brake pads. A good cleaning and a few strokes with a points file will take care of the rod.


#2 - You'll want to not just bleed your brake, but actually replace the fluid by bleeding until the fluid coming out is clear & clean.

I expect this will fix your problem. Ask Santa to bring you some new pads....
awsome suggestion,

but instead of a rag i recommend some clean & dry 800-1200(lite sand paper) be very gental. i had the same problem, i also had an annoying sound when rolling around, a good piston clean & bleed did the trick perfectly.

i don't know about getting new pads though, epically if you already just bought some new ones.
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post #9 of 11 (permalink) Old 12-13-2007, 07:04 AM
 
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Never, never use an abrasive compound, sandpaper or even scotchbrite for this purpose. It just isn't necessary and even the most careful application will damage the piston surface. I use MEK, but many other types of thinner will effortlessly wipe off the accumulated grit and crud without harming anything. I also use 'Q-Tips' to apply the thinner as this procedure avoids flooding the area and possible chemical attack on the rubber seals. Always be on the alert to avoid making the 'fix' worse than the problem. I also recommend using a piston ring spreader to make easy work of rotating the brake pistons around to expose inaccessible areas. You can get one from Snap-On for only $4,000. Just kidding, they're about $50.
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post #10 of 11 (permalink) Old 12-13-2007, 02:12 PM
 
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Quote:
Originally posted by DaveL
Never, never use an abrasive compound, sandpaper or even scotchbrite for this purpose. It just isn't necessary and even the most careful application will damage the piston surface. ...
Filo, I appreciate the compliment, but I gotta agree with DaveL about using abrasives on the piston. Sandpaper can leave scratches in the piston and loose grit which could abrade the sealing surface. Now you may have a light touch and good cleaning techniques, but someone not used to cleaning pistons
could do damage.

DaveL, I sold my 90 zx11 with107k miles....still was running great. I shoulda kept it..Best road bike I ever owned!
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