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Old 02-23-10, 12:51 PM   #1
corkscrew
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Avid Mtn BB7 arm not fully re-turning.

We've run into an issue with my roomie's Cannondale F700.

It has Avid BB7's (mountain version) on it. The rear caliper arm doesn't retract all the way after the brake is applied, this leaves the cable loose enough to settle against the top tube. It doesn't regain tension until the caliper arm is manually reset.

We used Park Tool's guide to adjust them initially, but saw no mention of this.
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Old 02-23-10, 01:05 PM   #2
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My initial thought is friction either at the brake lever or in the cable/housing. Is the BB7 and/or bike new/used?
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Old 02-23-10, 01:09 PM   #3
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If it's been exposed to the weather you should disassemble it and lubricate the area behind the piston. Both my BB5 and BB7 brakes suffered from corrosion in winter because they leave the factory dry.
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Old 02-23-10, 01:41 PM   #4
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If it's been exposed to the weather you should disassemble it and lubricate the area behind the piston. Both my BB5 and BB7 brakes suffered from corrosion in winter because they leave the factory dry.
In contrast, my BB7 hasn't need any additional lubrication so far this winter during which time it's been exposed to plenty of moisture and road salt. YMMV.
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Old 02-23-10, 05:41 PM   #5
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There is a spring adjustment screw that you can adjust the return spring tension with as well. Its under "Fine Tuning" in the user manual:

http://www.sram.com/en/service/avid/...D=1&subcatID=1
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Old 02-23-10, 06:35 PM   #6
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I'm also wondering about the cable/housing condition. Checking the spring tension on the caliper might help...
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Old 02-23-10, 09:35 PM   #7
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Yep, I'd first check the cable to housing friction on the section where it turns downwards at the seat tube. Also try disconnecting the cable from the caliper arm and see if it has a snappy return or if it is weak and maybe a little sticky.

It could be one of these things or it may be a combination of them adding up. If the bike is more than a few years old with lots of riding time start by changing out the cable and housings. That alone will really crispen up the brake lever feel. It won't STOP any faster but it'll feel a lot nicer. From there get in and clean and lube the caliper arm mechanism and adjust the spring from that point if needed. A few years of road grime can gum up the best of components.
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Old 02-26-10, 04:34 PM   #8
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Thanks for the info guys - I'll pass this on to my room mate.

The bike has seen some abuse, but is at the tail end of a full rebuild. The brakes came with it. We replaced the cables/housings last summer, but I'm guessing we didn't smooth out the housing cuts well enough.
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