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Do disc brakes require more adjustment?

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Do disc brakes require more adjustment?

Old 08-28-05, 03:49 PM
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FarHorizon
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Do disc brakes require more adjustment?

I've noticed that unless VERY accurately adjusted, the Avid Road Disc calipers on my Kona Dew will drag. The drag seems to be there at the beginning of every ride (change in humidity? change in temperature? nighttime-bike-adjusting gremlins?). I often stop several times during a ride to adjust the dials to eliminate drag.

I also notice that a hard turn will sometimes cause an intermittent brake squeal - worse on the rear disc than the front. Sometimes, the squeal will disappear by itself, sometimes I have to stop & adjust.

The actual impediment to the ride of such drag may be miniscule, though. If I stop, lift a tire, and spin it, I can hear the squeal, but the tire continues rotating without visible impediment.

So now questions:

1. Do disc brakes, in general, require more (and more accurate) adjustments than do rim calipers?
2. Does the audible squeal that I hear imply that I'm losing significant pedaling efficiency?
3. Is there something I don't know about disc adjustment (that my Avid installation guide didn't mention)?
4. Is the improved stopping efficiency of discs worth this amount of adjustment?

Thanks.
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Old 08-28-05, 05:30 PM
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Old Hammer Boy
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I have BB-7s on my Cannondale road tandem. They work great without the problems you describe, as long as they are properly adjusted. I really like them, and you should be happy with them, once they are correctly set up. The amount of clearance between the pads is a whole lot less than rim brakes, but they are a much more effective brake. On tandems, rim heating can be a problem, up to the point of blowing a tire. You certainly may be losing some efficency if they are dragging, but probably not too much. Here's how I adjust mine.

First, back out both adjuster knobs. Then, as you spin the wheel, adjust the inside adjuster until it just drags on the rotor. Now, back it off about 2-3 clicks. This should place it about 60% further into the braking zone than the outside pad. Now, as you spin the wheel, adjust the outside adjuster until it just drags. Back it off 2-3 clicks, too. Take up any excess slack with your brake cable adjuster.

If you've done this, and it didn't resolve your problem, you may be having a problem with the cable not slackining up. Also, make sure the rotor is properly aligned. That inside pad should be more than 50% of the showing pad surface without dragging. If it's not, you may have rotor alignment problems. Good luck... OHB
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Old 08-28-05, 05:33 PM
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I ran discs for a few months...
I didnt find they needed more adjustements. You really want to make sure that the rotor is centered between the pads so they engage properly. But once i had this set (easy using avid BB7's), I rarely had to fiddle with that.
Disc brakes rub, thats the nature of the beast if you ask me. But check to make sure the rotor is true, press it against a layout table or some other known to be flat surface.
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Old 08-28-05, 05:35 PM
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P.S. Make sure your tension (return) spring is adjusted to maximum return tension. Even with the longer cable associated with a tandem, I don't have the problems you describe.
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