A couple questions about Avid BBDB mechanical disc brakes
 

We picked up a 2004 Cannondale road tandem last year, and it's my first bike with disc brakes. So far I'm not thrilled, but I hope that's not the bike's fault.
We are getting lots of squeal, and worse, they don't stop very well. We do better on our other tandem with cantilevers.
So far I have replaced the pads with EBC gold.
Also, per installation instructions, I disconnected the cables, loosened the bolts (not the ones that bolt to the frame), dialed in the pads to grip the rotors, tightened everything back up. The pads still don't really seem like they are aligned. They have to be set pretty loose not to get rotor rub, and worse, they still squeal. Stopping isn't any better than it was before.
I found an overhaul document on the Sram/Avid archive, but it's for BB7, not BBDB. I know they are similar - enough so that I can go by this document? Or can someone point me to the overhaul instructions for BBDB brakes?
Anything else I should try? Thanks.

I should add that I'm pretty sure I bedded the brake pads correctly when I replaced them.

It's been a long time since I've touched BBDB brake, bur as I recall, the difference is the BBDB is one piece, the inner adjuster is different, some of them used a goofy sized rotor, and they have magnets to hold the pads in place instead of clips. The mechanics of how they work is the same, so instructions for a bb7 should be largely the same. They're pretty simple.

If they are squealing and not stopping very well, that is an indicator that the rotors have been contaminated with some type of oil. Try cleaning the rotors with some acetone or brake cleaner and abrade the rotors with some 220 grit emery cloth.

There are numerous ways that the rotors can be contaminated. It could be from lubing the chain, oils from the road mixing with water and splashing on the rotors(if you ride in the rain), overspray from sunscreen, etc.

Thanks for the replies. I did clean the rotors with alcohol, but it’s been awhile. I will try the acetone and light sanding.

Given how much my hydraulic Avid disc brakes sucked, my guess is this is even worse, and a losing proposition. Replacement with any Shimano hydraulic disc brakes would be a radical improvement. If it were me, and a tandem, I would take a look at quad-piston XT, along with new rotors.

BB meaning: ball bearing, DB meaning: disc brake ?
Yes, there are bearing balls inside, that contact the ramp ring that is attached to the actuating arm

which, when rotated, becomes sideways motion, making the pressure of the pad against the disc...

# 5 & 7 use this type of mech.. 7 adds the knob adjuster for the moving pad
both have the same stationary pad wear adjustment...




too hard to find anything on those? , ready to question your attachment to keeping them?





...

Some like TRP Spyre or Spyke , still mechanical ... 1 Road , the other MTB...
both pads move to the disc ,,







...

The only difference between the BBDB and the BB7 is the rear adjuster. The BB7 added a bolt for a 4mm Allen wrench to make them easier to turn. They use the same pad as a BB7...the one with two hooks on the top...and they are held in place by a spring clip on the top of the caliper. They are adjusted the same as the BB7.

The magnetic pad holder is in the BB5 (I think) and they are generally awful.

It also sounds like your rotors have a bend in them. Truing brake rotors is always a task that I find tedious and time consuming. I just use the brake pads as a gauge rather than a truing stand. It’s just easier.

Finally, it may be time to just punt and buy new rotors. Early Avid rotors weren’t particularly straight. I use Ashima on nearly all my bikes now. They are good and straight out of the box. They work quite well for me.

No, the early ("type F") BBDB used magnets to hold the pads in place against the piston and whatever the other side dohicky is called. The spring style works fine in the old calipers, in the event the magnets fall out, which they did. I don't know when the type N came out, but it wasn't around too long before they became BB7. The service guide for them, if you can find it (sram doesn't make it available anymore, they seem to want you to buy a new part), explains the other differences as well.

I did manage to find it eventually. At least I think I did. The url says BB7 but the document is titled BBDB Overhaul and seems to be the right one.
https://nuxx.net/files/bicycle/avid/...ul%20Guide.pdf

It's Business..
 

May pre date the Sram take over of the Avid Brand.. I heard BB5 was what Avid made at the time of the buy out.
The 7 was a redesign by the then Sram owned company..

You learn something every day.

That said, these are on a 2004 bike so they are more likely to be the newer spring type.

While that overhaul guide is helpful, I would heed the advice on page 4:

Your problems sound more like adjustment issues rather than a mechanical issue. I would suggest trying this guide on setting up BB7s before you go tearing the brake apart. The guide I linked to has helped me many times even when setting up non-Avid mechanical brakes. And look at your rotors.

Yes, the ones I (OP) have use springs.

Thanks. You are probably right. I don't think this bike has that many miles on it, and it seems unlikely that a full overhaul is necessary.
With regard to the guide you linked to, according to that I have just about everything wrong. The rear brake cable has a bare run along the top tube. I am not certain the housings are compressionless; will have to check that. The bike has 9 speed Ultegra STI levers, not the Avid ones the guide recommends.
As far as the Ashima rotors you linked to earlier, this bike has 200mm rotors. They do make this one, but at a quick glance I am not seeing it readily available. Will have to explore.

What is your rotor diameter? I know nothing of tandems. BB7's on my EM49.5 are awesome, 160mm rotors. SD-7 brake levers, 1 rider 170 lbs + 30 lbs bike, I can lock up and skid anywhere and everywhere, perfect modulation as well. If your pads are contaminated with road grease/oil they're not going to work well.

Rotors are 200mm. I have read that they are pretty decent brakes. I think I just need to get them set up right.

I found these if they help

http://my-sport.spb.ru/manual_1/ball...ce%20guide.pdf

https://www.servicearchive.sram.com/...03-install.pdf

The Ultra levers are probably be the problem. I don't think the BBDB brake came in a road version. The mountain bike version is made for long pull levers and the Ultregras are short pull. They won't work that well together. Road disc calipers need a shorter lever arm but you usually can't change it. You may need new calipers.

I don't use compressionless housing but I'm also using the brakes on a single. I also have a run of bare wire for the rear brake (the green outer cable on the picture below) and I've never had issues.

https://live.staticflickr.com/65535/...3258b652_o.jpgUntitled by Stuart Black, on Flickr

The bike doesn't currently have BB7s on it but it has had BB7, TRP Spykes and Paul Klampers (current brake). None of them have had issues with performance. The Klampers, by the way, allow for changing the lever arm so that the brake can be used on either road or mountain. The only downside is that arms cost almost as much as a new BB7 Caliper. You can buy 8 sets of the BB7 for the cost of a set of Klampers. Cool brakes but they are pricey.

I use 203mm rotors. You could probably use a 203 as well. You just need the proper adaptor which are relatively cheap.

https://live.staticflickr.com/65535/...03af63dc_o.jpgUntitled by Stuart Black, on Flickr

Any reason Travel Agents wouldn't solve the cable pull issue? [edit] I see it says linear pull brakes only. Maybe this won't work, although I'm not sure why.
https://northwestbicycle.com/product...iABEgL-h_D_BwE

I can see your point about the levers, but I tend to think I have some alignment issues as well. I think my approach will be as follows:

1. True and clean the rotors.
2. Try the caliper alignment procedure again.
3. If performance is still sub-par, add travel agents. (or not; see above)
4. If still sub-par, replace rotors.

It might. I've never had much luck with Travel Agents. I found it easier to either use the proper lever or the proper brake. If the bike has long pull levers, I'd use linear or mountain disc. If the bike has short pull, I'd use cantilevers or road disc. I don't have any road bikes with discs, however.

The other question is where you would put the travel agent on a disc brake. The 90° turn is going to make for a funky cabling on the caliper. A straight version for a disc would work much better.

The TA I linked replaces the noodle on a v-brake. So I can’t see it working here.
Problem Solvers apparently used to make an inline version, but unfortunately it’s discontinued.

Good news. My calipers are marked Road, so I take that to mean I should be able to get them working acceptably with my STI levers.