Avid BB5 rear caliper - no stopping power without pads rubbing on disc
rodgers73
Posts: 2,626
Firstly, I have been a road rider for around 6 years and have only just begun using a hybrid in Jan with mechanical disc brakes on it. So, I'm very new to this system, although relatively handy with bike mechanics. With that in mind, please forgive a possibly naïve question...
My rear brakes developed a noise recently that sounded very much like the disc was rubbing on the pads without the lever being pulled. After a lot of fiddling and watching of YouTube instructional videos I concluded that the issue was a warped disc. I've just fitted a new disc today and the issue is still there.
So far, this is what I have tried (having already centred the caliper) -
1. I wind the inner pad-wheel-thingy out as far as it will go, then insert the brake pads and then slowly wind it back in until the inner pad is as close to the disc as it can go without touching
2. I tighten the cable on the torque arm by loosening the retaining nut and pulling it through with pliers then retightening. I then use the barrel adjusters on the caliper and on the lever to tighten the cable further to the point where the tension is such that any further and I begin to hear friction between outer pad and disc.
3. So, the brake SEEMS correctly set up yet when I ride the bike and try and stop there is very little in the rear brake's stopping power. The lever is being pulled as far as it will go and only minimal retardation occurs. All the work is being done by the front caliper, to the point where I think that there is actually a fault wiith the rear caliper as it cannot possibly be designed to be so weak.
4. The only way I can get a properly functioning rear brake is to tighten it to the point that I can hear the pad and disc rubbing as I ride along - but at least I can stop!
So, am I missing something here? Is there maybe a problem with the rear caliper itself? I'm genuinely in the dark as to what sort of problem that might be - the piston not working properly or something? No clue to be honest given my few months of experience with disc brakes!
(I've tried googling and also youtube vids but no joy - sorry if this seems like a stupid question to you old hands!)
My rear brakes developed a noise recently that sounded very much like the disc was rubbing on the pads without the lever being pulled. After a lot of fiddling and watching of YouTube instructional videos I concluded that the issue was a warped disc. I've just fitted a new disc today and the issue is still there.
So far, this is what I have tried (having already centred the caliper) -
1. I wind the inner pad-wheel-thingy out as far as it will go, then insert the brake pads and then slowly wind it back in until the inner pad is as close to the disc as it can go without touching
2. I tighten the cable on the torque arm by loosening the retaining nut and pulling it through with pliers then retightening. I then use the barrel adjusters on the caliper and on the lever to tighten the cable further to the point where the tension is such that any further and I begin to hear friction between outer pad and disc.
3. So, the brake SEEMS correctly set up yet when I ride the bike and try and stop there is very little in the rear brake's stopping power. The lever is being pulled as far as it will go and only minimal retardation occurs. All the work is being done by the front caliper, to the point where I think that there is actually a fault wiith the rear caliper as it cannot possibly be designed to be so weak.
4. The only way I can get a properly functioning rear brake is to tighten it to the point that I can hear the pad and disc rubbing as I ride along - but at least I can stop!
So, am I missing something here? Is there maybe a problem with the rear caliper itself? I'm genuinely in the dark as to what sort of problem that might be - the piston not working properly or something? No clue to be honest given my few months of experience with disc brakes!
(I've tried googling and also youtube vids but no joy - sorry if this seems like a stupid question to you old hands!)
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Comments
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Sounds like the rear pads are contaminated, does the lever pull back to the bar or does it feel like the front?Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0
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The lever pulls back in the normal way - I've had the pads out and cleaned them with brake cleaner so they should be ok0
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Brake cleaner, if it's for cars, is likely to contaminate them more.I don't do smileys.
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Parktools0 -
No, it made my front brake better. Sharper. Plus, I've had the problem I'm talking about before I used the cleaner so I don't think that is the problem.
Do the pistons ever jam slightly? Could it be that it isn't retracting properly after the lever is pulled?0 -
How would it not retracting lose brake power?Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0
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The braking power is affected by the fact that the pads are rubbing on the disc unless I wind the pads so far out that the stopping power is minimal.
Do you think this is caused by the piston not fully retracting?0 -
No.....
You should wind the pads out until they 'just' start to rub, that is the best setting, if you have a warped disc then you'll never get it working right.Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0 -
I know, I've tried that AND fitted a new disc.
What I'm querying is should the stopping power of the brake be SO weak at the point where the pads are not rubbing on the disc? Surely not given that disc brakes are sold on the basis that they provide a lot of stopping power.
Therefore, something isn't quite right with the caliper (it seems) - unless someone knows what else the problem might be?0 -
No idea- just get shimano m395 hydraulic brakes, even those will be much better-Cube Acid 29" 2013
-A new Giant Trance 3 2015!0 -
BB5 are excellent brakes, better than many entry level hydraulic, my son used to have a set on his old MTB.
Performance drop off as the pads are spaced out is purely down to the loss of mechanical advantage (leverage) at the lever.
Have you made certain the calliper is aligned right to the disk? The CPS washers means its very easy for it to be mounted at an angle and that will mean issues with excessive lever travel and leverage,Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.0
