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  1. #1
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    Avid BB7 Mechanicals

    I just did my first snowy ride on my new BB7 discs (I have done dozens of rides with them in the dry/dirt). The brakes worked well at first, but about an hour into the ride, I had no rear braking. I stopped and confirmed that the cable and levers were working properly. It seemed like the calipers were properly squeezing the disc, but the disc was "slipping" through without enough friction. About an hour later on the same ride, I got perfect braking again. And again an hour later the same thing happened.

    The pads probably have 150 miles on them and the setup is new all around. I didn't see any obvious ice on the disc, but everything was snowy so hard to tell. Any ideas what causes this and the best way to prevent it? Now that the bike is back in my warm basement, it works fine.

    Thanks,
    Len

  2. #2
    No, that's not phonetic
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    The pads will get glazed with ice. No friction means no heat to melt the ice. Just drag your brakes briefly every 30 seconds to keep the ice off the pads.
    My video techniques can be found in this thread.

  3. #3
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by lennyzen View Post
    I just did my first snowy ride on my new BB7 discs (I have done dozens of rides with them in the dry/dirt). The brakes worked well at first, but about an hour into the ride, I had no rear braking. I stopped and confirmed that the cable and levers were working properly. It seemed like the calipers were properly squeezing the disc, but the disc was "slipping" through without enough friction. About an hour later on the same ride, I got perfect braking again. And again an hour later the same thing happened.

    The pads probably have 150 miles on them and the setup is new all around. I didn't see any obvious ice on the disc, but everything was snowy so hard to tell. Any ideas what causes this and the best way to prevent it? Now that the bike is back in my warm basement, it works fine.

    Thanks,
    Len
    The brakes are not bedded in yet, either.

    With brand new pads and rotors I usually need to run the pads "tighter" than normal for a ride or to. Often then need to loosen the pads a couple of clicks.
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  4. #4
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    Quote Originally Posted by shiggy View Post
    The brakes are not bedded in yet, either.

    With brand new pads and rotors I usually need to run the pads "tighter" than normal for a ride or to. Often then need to loosen the pads a couple of clicks.
    Wow. So many posts, such mediocre help. There is an actual brake bed in procedure recommended by the manufacturer of your brakes. It sounds like your pads have 150 miles but new rotors? You then need to follow the new brake procedure, assuming this has anything to do with your loss of brake power. SRAM recommends you do ten medium speed to walking speed slow downs. Do not come to come a complete stop. Then do ten high speed to walking speed slow downs. Let rotors completely cool. Go ride. This will maximize power while eliminating squealing.

  5. #5
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    It does sound more like ice though.

  6. #6
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    Quote Originally Posted by atom29 View Post
    ...SRAM recommends you do ten medium speed to walking speed slow downs. Do not come to come a complete stop. Then do ten high speed to walking speed slow downs. Let rotors completely cool. Go ride. This will maximize power while eliminating squealing.
    It's never eliminated squealing for me for longer than it takes to find the first puddle.

    I think that having to do all this faff on a brand new brake is a sign that something is wrong with quality control/materials choice. Surely the pads should be bedded to the rotor by the manufacturer.

    Maybe fair enough for replacement pads, but that is still too much faff.

    (And yes, I do know how to set up a BB7 properly)
    As little bike as possible, as silent as possible.
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  7. #7
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    Quote Originally Posted by Velobike View Post
    It's never eliminated squealing for me for longer than it takes to find the first puddle.

    I think that having to do all this faff on a brand new brake is a sign that something is wrong with quality control/materials choice. Surely the pads should be bedded to the rotor by the manufacturer.
    I don't have any disc brakes that don't squeal when wet, but none of my discs squeal when dry.

    Brakes like any part of your bike need some love. I don't do anything special when I get new disc brakes or new pads, but I am aware they need some time before they'll perform their best. I've never found that to be too much effort to handle.

    FWIW:

    - car & motorcycle discs are the same. It's not a design or QC failure.

    - new tires need to be ridden conservatively at first while you break them in as well to get full traction.

    - your suspension fork will work better after a few rides onces everything has broken in together....same with your internal gear hub.
    Safe riding,

    Vik
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  8. #8
    Nouveau Retrogrouch SuperModerator
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    Quote Originally Posted by atom29 View Post
    Wow. So many posts, such mediocre help. There is an actual brake bed in procedure recommended by the manufacturer of your brakes. It sounds like your pads have 150 miles but new rotors? You then need to follow the new brake procedure, assuming this has anything to do with your loss of brake power. SRAM recommends you do ten medium speed to walking speed slow downs. Do not come to come a complete stop. Then do ten high speed to walking speed slow downs. Let rotors completely cool. Go ride. This will maximize power while eliminating squealing.
    And what do you do when the official break in procedure does little to nothing?

    In 11 years of using Avid brakes my simple method of tightening the pads, ride and adjust as needed works best for me.

    It may not be Lenny's problem, but it is a possibility. No matter how much you want them, there are no absolutes, especially when trying to fix something over the Internet.

    Edit: I did miss that lenny has ridden the brakes in the dry before this. They likely are bedded in.
    It could be the pad compound. I have found Avid branded pad compounds to be less than consistent in the wet/snow. Organic is the worst (any brand), just loses power in the wet/snow. The Avid brand metallic can be good or can be terrible in the wet, needing to be tightened during wet rides, then backed off again when dry.
    I have never had the above issues using EBC Gold pads.
    Last edited by shiggy; 01-22-2012 at 06:15 PM.
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  9. #9
    Nemophilist
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    Hey;

    Very few people understand how friction material brakes really work, so it's not surprising to see such a wide variety of "opinions" and "experiences." In reality, the bed in process accomplishes many things and is important - even crucial - for many reasons.

    People think that the surface of a rotor is perfect for stopping right out of the package, and this is simply not the case. It takes burnishing by the brake pad to prepare the rotor surface for optimal grip. In the case of a car, a freshly turned rotor is FAR too rough to stop well at all. Even a brand new rotor is not conducive to stopping well. Use in the environment it will live in is the only way to prepare them.

    The burnishing process is equally as important for the pads. Among the many materials in a brake pad are materials that are necessary to the production process, and these are not conducive to helping the brakes work. These need to be burned off. There are resins that bind the metallic and/or organic particles together. These need to be activated. When you do a proper bedding, you are burning off the release agents and other byproducts of the production process. If you do a proper bedding, you will note that as you get into the more aggressive portion of the process, the stopping ability decreases markedly. What you are experiencing is the release agents from production creating first a physical (liquid) and then a gaseous boundary layer between the pad and rotor that actually prevent the brakes form grabbing effectively. Once you have burned off these materials and allowed the brakes to cool, you will note an immediate and dramatic improvement in stopping. You have arrived. Any substance that lands on the surface of the brakes will alter that relationship to varying degrees, and needs to be worked off the surfaces, either by use or maintenance.

    While the mechanical friction components of the pad are surfacing the rotor, and the oils from production are being burned off through the heat derived from this friction, there is something even more esoteric taking place. There are resins in the pads that are being melted and transferred to the rotor surface. When you have the same resin in the pad as on the rotor surface, and you add a little heat, you have not only a mechanical but a chemical friction relationship that will give you the best braking performance available. The chemical interface between surfaces actually does more of the stopping than simple friction does. The friction aspect (turning motion into heat) is almost more import because it activates this "chemical grip." Without the chemical, the mechanical wouldn't stop you for squat.

    Change rotors and you need to burnish them. Change to new pads, and you have to burn off the oils again. Change to a different pad type, and you not only have to burn off the oils, but remove the old resin and transfer that type of resin to the rotor surface for optimal braking performance.

    Simple, eh?
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  10. #10
    Nemophilist
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    And further;

    Even if your brakes are bedded to perfection, and you never go through any water or snow, you can completely lose brake performance in the cold. Any heat that dissipates from the rotors as they cool can cause condensation on the rotor surface that will freeze if there is not enough friction to keep things warm. Either you rely on static drag from your brake system, or you drag them manually to keep things warm and dry.

    Just be glad you have discs!
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
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  11. #11
    @adelorenzo
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    It doesn't matter how well your brakes are bedded in when your rotors are frozen or iced up. Not having any braking is a normal occurrence when you ride in cold and snow, just squeeze the brakes until they warm up enough to start helping you stop.

  12. #12
    will rant for food
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    Yep. Ice.

    Consider it a mild workout additive when you're pedaling and the rear brake kicks in. You'll get the rhythm.

    EDIT: You know how, when driving a car with "all weather" tires on snow, they'll pack up, and once you hit dry pavement again, you can't just hit the gas because you're still driving with basically snowy tires? Same thing. Gotta wait for that stuff to peel off, THEN floor it. But, I drive like a dick.

    Thread jack: Velobike, you've had experience with drum brakes in mud, how do those compare to discs in icy conditions? Does it get cold enough in your neck of the woods?
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  13. #13
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    Quote Originally Posted by Drew Diller View Post
    ...Velobike, you've had experience with drum brakes in mud, how do those compare to discs in icy conditions? Does it get cold enough in your neck of the woods?
    Gets down to -20C but more usually -10C is the low point, so not as cold as many North American riders are experiencing. We get an awful lot of wet cold though around the -5 to +5 mark and I'd sooner have -20C any day.

    My discs work pretty well. I do bed them in properly - my only beef with them is the way they get through pads when our trails are muddy. Mica and granite tends to be a bit abrasive. Apparently it cleans the rotors of all the conditioning so the pads wear out in double quick time.

    The drums are totally troublefree - being enclosed they don't seem to get any problems, and that is very much appreciated in mud.

    However I'm generally not going fast enough in really cold conditions to really stress the brakes.

    One bonus of the S-A drum brakes is how beautifully they roll. Spin the wheel and it will keep going and going and going - just like an old Campag hub. I don't get that with my disc braked wheels.
    As little bike as possible, as silent as possible.
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