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Old 05-13-08, 10:28 PM   #1
kill.cactus
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Disk brake grief

Problem: Disk brakes offering near-zero stopping force

Examination: I've had my disks (avid bb5s) for a while. They've never really stopped as well as some other disk equipped bikes I've ridden (I've ridden other bikes with bb5s and I think maguras as well) but they've done enough in the rain and dirty to justify their not so goodness with stopping when it is dry out. Lately I've had issues with the stopping power getting less and less. I've always been careful never to get oils on the rotors or pads. Eventually I got really upset with the fact that I can stop as fast on my road bike with sucky calipers as I could with my disks so I took the pads out and cleaned them.

Cleaning process: Soaked for 5 or so seconds in rubbing alcohol, dried with paper towel and rubbed the surface with semi coarse sandpaper. Didn't touch the pads with my fingers or any source of oil at all.

Result: Since the cleaning, I've lost all braking power. Literally from about 1 mph (according to my cyclocomputer) the rear brake engaged AS HARD AS POSSIBLE will stop me in about two and a half feet. The front brake will stop me in about a foot and a half. From less than 1 mph (too slow for my computer to pick up) the rear brake stopped me in about a foot and a half. Front in about a foot.

WTF

So I rode the bike in a sandbox since I've heard that braking power is reduced after initial cleaning and only is restored after "grit" has settled into the pads. I even kind of threw some sandy mud onto the rotors and rode another few hundred meters stop go stop go (mind you that the stop motion would take up to 10 feet if I was going anything more than 2mph...).

NOTHING

I'm completely out of ideas - what has happened to my brakes?
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Old 05-13-08, 10:31 PM   #2
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Originally Posted by kill.cactus View Post
Problem: Disk brakes offering near-zero stopping force

Examination: I've had my disks (avid bb5s) for a while. They've never really stopped as well as some other disk equipped bikes I've ridden (I've ridden other bikes with bb5s and I think maguras as well) but they've done enough in the rain and dirty to justify their not so goodness with stopping when it is dry out. Lately I've had issues with the stopping power getting less and less. I've always been careful never to get oils on the rotors or pads. Eventually I got really upset with the fact that I can stop as fast on my road bike with sucky calipers as I could with my disks so I took the pads out and cleaned them.

Cleaning process: Soaked for 5 or so seconds in rubbing alcohol, dried with paper towel and rubbed the surface with semi coarse sandpaper. Didn't touch the pads with my fingers or any source of oil at all.

Result: Since the cleaning, I've lost all braking power. Literally from about 1 mph (according to my cyclocomputer) the rear brake engaged AS HARD AS POSSIBLE will stop me in about two and a half feet. The front brake will stop me in about a foot and a half. From less than 1 mph (too slow for my computer to pick up) the rear brake stopped me in about a foot and a half. Front in about a foot.

WTF

So I rode the bike in a sandbox since I've heard that braking power is reduced after initial cleaning and only is restored after "grit" has settled into the pads. I even kind of threw some sandy mud onto the rotors and rode another few hundred meters stop go stop go (mind you that the stop motion would take up to 10 feet if I was going anything more than 2mph...).

NOTHING

I'm completely out of ideas - what has happened to my brakes?
When's the last time you replaced your pads?
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Old 05-13-08, 10:33 PM   #3
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When's the last time you replaced your pads?
They've only been used about four hundred miles.

And when I talk about "when I first got my BB5s" I really meant "when I last replaced the pads" although truly the disks I'm running never really worked nearly as well as I had thought they should...
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Old 05-13-08, 10:41 PM   #4
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They've only been used about four hundred miles.

And when I talk about "when I first got my BB5s" I really meant "when I last replaced the pads" although truly the disks I'm running never really worked nearly as well as I had thought they should...
Have you fiddled with the barrel adjusters or the caliper at all? Are the pads actually making goood contact with the brake? What about your brake lines?
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Old 05-13-08, 10:50 PM   #5
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Have you fiddled with the barrel adjusters or the caliper at all? Are the pads actually making goood contact with the brake? What about your brake lines?
Checked. Perfect contact settings and the brake lines are as smooth as they've ever been (cleaned them a little while ago)
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Old 05-14-08, 08:43 AM   #6
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Did you also clean the rotors?
How much of a gap is there between the pads and the rotor when the brakes aren't engaged?
How far do you pull the brake levers before the pads start rubbing on the discs?
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Old 05-14-08, 10:21 AM   #7
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I have a sneaky feeling that one pad is engaging the rotor into the caliper body.

Look at the pad that doesn't move inward when you sqeeze the lever. Is it protruding past the caliper body?

Adjust the barrel adjuster out, and adjust the non-moving pad inward. Re-align the caliper if necessary. When that non-moving pad gets worn down...it doesn't automatically adjust itself closer to the rotor.


harliej got a set of BB5's and they were doing this. I was very dissapointed in the performance until I noticed what was going on. His moving pad was pushing the metal rotor into the metal caliper body...steel on steel doesn't stop well. I adjusted the non-moving pad inward and it increased braking power 150%. After that, I became and Avid Mech fan.

Last edited by ed; 05-14-08 at 10:28 AM.
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Old 05-14-08, 10:25 AM   #8
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Originally Posted by kill.cactus View Post
So I rode the bike in a sandbox since I've heard that braking power is reduced after initial cleaning and only is restored after "grit" has settled into the pads.
That's wrong. When you wash your bike...soap and water gets on the pads. About 1 block of braking will burn that crap back off. You don't need dirt on your pads for them to work properly. You don't WANT sand in there b/c it will score the rotor.

The "grit" that someone told you about is when the breaks "burn in"...or burnish. (or something like that) The only thing you need do in the sandbox is pee.
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Old 05-15-08, 02:20 AM   #9
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Originally Posted by kill.cactus View Post
Problem: Disk brakes offering near-zero stopping force

Examination: I've had my disks (avid bb5s) for a while. They've never really stopped as well as some other disk equipped bikes I've ridden (I've ridden other bikes with bb5s and I think maguras as well) but they've done enough in the rain and dirty to justify their not so goodness with stopping when it is dry out. Lately I've had issues with the stopping power getting less and less. I've always been careful never to get oils on the rotors or pads. Eventually I got really upset with the fact that I can stop as fast on my road bike with sucky calipers as I could with my disks so I took the pads out and cleaned them.

Cleaning process: Soaked for 5 or so seconds in rubbing alcohol, dried with paper towel and rubbed the surface with semi coarse sandpaper. Didn't touch the pads with my fingers or any source of oil at all.

Result: Since the cleaning, I've lost all braking power. Literally from about 1 mph (according to my cyclocomputer) the rear brake engaged AS HARD AS POSSIBLE will stop me in about two and a half feet. The front brake will stop me in about a foot and a half. From less than 1 mph (too slow for my computer to pick up) the rear brake stopped me in about a foot and a half. Front in about a foot.

WTF

So I rode the bike in a sandbox since I've heard that braking power is reduced after initial cleaning and only is restored after "grit" has settled into the pads. I even kind of threw some sandy mud onto the rotors and rode another few hundred meters stop go stop go (mind you that the stop motion would take up to 10 feet if I was going anything more than 2mph...).

NOTHING

I'm completely out of ideas - what has happened to my brakes?
after giving careful consideration to your post, i think the problem is cable actuated disc brakes. you're trying to make your bb5's something they just weren't meant to be.

you should probably just replace your brakes with some real hydraulic brakes.

good luck

mx
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Old 05-16-08, 04:20 AM   #10
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Originally Posted by mx_599 View Post
after giving careful consideration to your post, i think the problem is cable actuated disc brakes. you're trying to make your bb5's something they just weren't meant to be.

you should probably just replace your brakes with some real hydraulic brakes.

good luck

mx
Looking at the stopping distances that he quoted, I think there is an actual problem with them and it's not that he expects them to do something that they won't do. Mechanical disc brakes should perform better than the way these ones are.
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Old 05-16-08, 05:01 AM   #11
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Looking at the stopping distances that he quoted, I think there is an actual problem with them and it's not that he expects them to do something that they won't do. Mechanical disc brakes should perform better than the way these ones are.
oh, okay. i didn't actually read any of the original post. i just noticed the BB5's and jumped on it.

mx
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Old 05-16-08, 05:11 AM   #12
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Take your bike to your local bike shop and have a mechanic adjust the brakes. It's an easy DIY but if you don't know how to adjust them then you'll just end up where you are today: brakes that don't work.

My guess is your brakes aren't adjusted right and the brake lever is barely causing the pads to contact the rotors (or not at all).
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Old 05-16-08, 11:45 AM   #13
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after giving careful consideration to your post, i think the problem is cable actuated disc brakes. you're trying to make your bb5's something they just weren't meant to be.

you should probably just replace your brakes with some real hydraulic brakes.

good luck

mx
No need for Hydros
I have Shimano Deore M-475 Mech (cable) calipers on LX rotors with Deore V-Brake levers and these have ALWAYS stopped me so quickly its scary!! I pull a B.o.B. and Pannier regularly with up to 100 lbs in or on.
sounds like either pad glasing (stopping too hard before the pads are bedded in) or they are horribly out of ajustment.
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Old 05-16-08, 08:46 PM   #14
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after giving careful consideration to your post, i think the problem is cable actuated disc brakes. you're trying to make your bb5's something they just weren't meant to be.

you should probably just replace your brakes with some real hydraulic brakes.

good luck

mx
hopefully this is sarcasm...
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Old 05-16-08, 08:47 PM   #15
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oh, okay. i didn't actually read any of the original post. i just noticed the BB5's and jumped on it.

mx
oh haha
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Old 05-16-08, 08:48 PM   #16
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I'm taking the bike to the mechanic - we'll see what happens
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