[Doggus]

LBS installed a new BB7 on our tandem and it was working fine for a few rides. Couple rides back it started to 'feel like' the calipers were clamping down on BBs (best way I can describe it, also pardon the BB pun). Then last night the vibration got worse and the brake is now useless. When I apply braking pressure it starts to vibrate so bad that it will not take hold and brake. I'm sure it's a small adjustment of some sort.

I cleaned the disc with alcohol and checked for any loose parts, which I found none. I turned the inboard adjustment knob a couple of twists to decrease the pad spacing.

Any ideas what might be causing the vibrating on these brakes? Simple adjustment?

[The BikeForums Team]

This is an archived thread, you can find the full version of this thread, with images, links and more content here.

Ready to buy? Check out these two online bike stores:
- http://www.nashbar.com (you can find the latest bike nashbar coupons in this thread)
- http://www.performancebike.com (you can find the latest performance bike coupons in this thread)

Cya on the forums,
- The BikeForums Team
- http://www.bikeforums.net

[TandemGeek]

What you describe could be so many things that I'd suggest you start from scratch following Avid's instructions which you can download from the Web: http://sram.com/_media/techdocs/bbdb-mtn-160-install.pdf

There are some other comments in this thread that may be of use: http://www.bikeforums.net/showthread.php?t=280966&

The things that immediately come to mind are:

1. You've already addressed this one: a loose bolt on the attachment hardware or perhaps the bolts that fasten the rotor to the hub or rotor adapter could be loose. Any loose hardware on a disc will create all kinds of annoying problems, ranging from "chatter" to brake squeal, to other performance issues... not to mention lost parts.

2. The brake pad material has become contaminated OR may be the wrong type of pads. Avid had a problem early on with a production lot where the brakes were accidentally fitted with incredibly fast-wearing pads -- I forget why they even existed at the moment -- and folks were burning through them in days or even hours, not years or months. Avid warrantied replacement pads, etc... and fixed the problem but not knowing where the Avid's came from and how old they may be (i.e., New Old Stock / NOS) it would be something to look at.

3. The inboard pad could have been set too close to the caliper and when you apply the brakes the rotor is being pushed into the caliper instead of the brake pad material. This can also happen as the pads wear down so if anyone with an Avid ever starts to hear an awful, metallic sound coming from their rear disc, check the inboard pad placement and wear.

Again, if it was me, I'd pull off the pads (it's very easy and covered in the linked-to instructions) and give them a good look-see to make sure they weren't showing any unusual signs of wear or contaminants (something on or in the pad material that should be there). If they check out OK, reinstall the brakes following the Avid instructions and then see if the problem is resolved.

[Rincewind8]

Could it be a warped/bent rotor?

[zonatandem]

Something to be said for V-brakes . . .

[TandemGeek]

Something to be said for V-brakes . . .

Yes, thank goodness V-brakes and cantilevers in general are immune from problems. :rolleyes:

[prairie*boy]

Doggus:

Is the wheel hub tight? I just had a similar problem on my commuter and the problem wasn't the Avid caliper or the disc, but the hub on the wheel...It was just a little loose and allowed a vibration to get started. A quick readjustment of the wheel and I was off.

Now if I could only figure out how to quiet the V-brakes on the tandem - XT with Salsa CF brake booster (probably not set up right). Hope Mono 6 Ti in back is quiet and powerful...

Trying to assist (not hijack your thread)

Prairie*boy

[Doggus]

I will check tonight. I found on last nights ride that if I vary the squeeze on the lever I can 'feel' it through the vibration and actually get it to take hold. Shouldn't have to work like this though. May end up going back to the shop if I can't figure it out myself.