Avid BB7: infinite frustration

[cooperplace]

I replaced the pads on the above, c r c sent me a replacement set because of the howl, and I've spent the whole !(AT)#$% day trying to get it to run right.

I still can't get it to run without dragging AND it has excessive lever travel.

Is there someone out there who lives, breathes, dreams about these things?

Needless to say, I've downloaded the Avid tech manual, read the instructions, watched the Youtube videos, etc etc, to no avail. There is in my opinion a slight amount of runout in the disc. Also it is best (but still not good) with the caliper shimmed about 0.8mm inboard.

Any suggestions? But please, only from people who own and/or service these units.

[cooperplace]

before anyone asks, the unit operates smoothly, the return springs return, it's not an issue of the caliper failing to spring back.

[MichaelB]

Hi Peter,

I have a couple of spare new discs (both roundagon) if you want to try that to eliminate a potential cause ? PM me if interested.

I have had very liitle howl with the G2 cleansweep, but that doesn't help you.

Haven't done much fiddling on mine, but about to help a mate setup one on his bike (185mm roundagon on a steel fork), so may learn sonething from that ?

In the thread on my conversion, there were several posts re a technique to set it up whereby the bolts are loosened, the brakes applied, and then bolts re done up (some steps may be missing) ?

Drop by if you want another set of eyes on it ?

Cheers

Michael B

[janus77]

i read a review on how to get around the avid turkey gobble.. there was something about htem not being designed perfectly, so there was a need to put an extra washer on the back of one of the pads.

will have a look and see if i can find the article, it had a full run down on how to get them set up to avoid it.

[Nobody]

First step should be to try some organic/soft pads that are quiet. That should fix or reduce the problem.

[cooperplace]

the replacement pads are organic, and hopefully they will cure the noise. But to get it set up so that it doesn't drag, the lever comes all the in to the handlebar = no braking, a separate problem.

[zero]

On my deore hydro's, the pads do not always follow the pistons out, and it causes continuous squeaking and rubbing sounds, and when its happening the wheel is not a particularly free spinner. The pistons are known to be retracting properly because I can see them retracting from the pads (ie gap appears between pistons and pads), and the spring is there, but its not pushing them apart, or it pushes one pad a long way. It went away when I changed the pads and spring last time, but it is back again now the pads are worn.

BB7s appear to have a loosely similar spring and guide system, and probably it gets fouled with brake dust/corroded from wet days/whatever. Perhaps the spring supplied is weak, or maybe by setting the mechanism loose - you make enough space that the easier to move pad can move a long way and thus there is less ongoing tension on the more difficult to move pad.

If you can get a knife between the pads and disc and push pads back and get a free spinner, then you can isolate alignment from pads/mech retraction as the problem.

[cooperplace]

brand new pads and spring, all pulled apart and cleaned out. Squeaky clean in there: no dust at all. I actually can't see where it's dragging: it's such a tiny space in there. But I don't think it's a retraction issue.

[Uncle Grumpy]

First step should be to try some organic/soft pads that are quiet. That should fix or reduce the problem.

I'm not a fan of soft pads on cable discs. On hydros they are okay because hydros compensate for pad wear automatically. My first set of discs were BB7s (still have them in fact) and I was entered in a downhill race. So I threw in some soft pads for extra stopping grunt, set up the brakes nicely. First run, and by the end of it, I was out of brakes, lever to the bars. Thinking something was wrong, I set them up again, did the next run at a suitably scorching time. End of it, no brakes, lever to the bars.

Turns out I was chewing the pads out each run. 2 practice runs and 2 race runs and I was down to metal on metal. Sub 20 minutes of hard riding. Cool. So I don't recommend soft compound pads in cable discs.

As to the OPs problem, they can be a PITA to set up. I get mine right by doing the following:

1. Set the inside pad up close to the rotor.

2. Set the lever up (no cable at this point) with the barrel adjuster turned out, ie: as though you were tightening the cable as far as you can.

3. Cable up the caliper with the piston actuating arm closed, ie: so it pulls the pad against the rotor.

4. Holding it in that spot, pull the cable through taut and tighten the cable. Yes, having a third hand or a helper here does help.

5. So now there should be no lever travel and the rotor should be locked.

6. Wind in the barrel adjuster to get some slack into the cable until you get some movement in the piston arm.

7. Fine tune the outer pad with it's dial.

Good luck.

Grumps

[cooperplace]

OK! Thank you! I will give it a go.

[cooperplace]

MichaelB dropped a spare disc in to my house tonite and after playing with it, I think I have found a solution.

Like the police when dealing with a murder, I am obliged to notify Michael first, then I will post my findings. I have to say that this issue, which has been ruining my life and almost driving me to drink (actually i'm already there), I wouldn't have solved without Michael's great help and I'm indebted to him.

[Kalgrm]

I've been running the Goodrich sintered pads on mine for several years now with very few problems. They squeak if they get wet, but soon dry out and are quiet again once they do. (I run the Goodrich pads on all three sets of Avid brakes I own. Great stopping power and quiet.)

The excessive lever travel is a worry. Do you have too much cable housing installed? That would allow the housing to move around, absorbing some of the power you're applying.

Good to hear something is afoot though.

Cheers,
Graeme

[Bentnose]

I'd pulled my pads out on my BB7's to have a look at them, according to the new set it is a no tool operation. Had pull hard with the long nose pliers to get them out. After I had them back in I had severe problem with rubbing, found I had to get the long nose on each pad and give them a very hard push to get them properly seated.

[cooperplace]

I'd pulled my pads out on my BB7's to have a look at them, according to the new set it is a no tool operation. Had pull hard with the long nose pliers to get them out. After I had them back in I had severe problem with rubbing, found I had to get the long nose on each pad and give them a very hard push to get them properly seated.

yes, I went through that as well. You or I could do a better job of writing the instructions. But that wasn't the issue.

[MichaelB]

Peter, replied to your PM, and it seems that my thoughts re the disc tab alignment were correct.

Glad to see there is potentially some light at the end of the tunnel, and it isn't a train comiong the other way !!!

No hurry to return the disc

[MichaelB]

OK Peter, the suspense is killinmg me, what's the verdict ?

Have you found a solution ? .....

[jackthelad]

have the Disc Brake Tabs been faced square, on the fork?

I have 3 sets of avid brakes,
and apart from the odd squeal, generally never any problem

including bb7s on my commuter

my tips
don't use the barrell adjusters at all/screw them all the way in.
adjust pads till the are close to the disc with the stationary pad closer to disc than moving pad, as per manual
this is important..
Then when u get lever feel u are happy with
Loosen Caliper bolts
pull brake lever tight
Hold lever and tighten caliper Bolts
spin wheel , and see how true it runs

2 other things
Clean Disc with isopropyl alcohol or Nulon Brake Clean
check disc is straight or hub mounts are faced/level...

Jack


i
i

[cooperplace]

I fitted the Kinesis DC19 fork and the new organic pads that c r c sent under warranty. Result:

1. Brakes instantly align and adjust up perfectly (what a joy).
2. Braking is powerful and dead quiet, although I've yet to fully bed in the pads.

A huge improvement. Thanks again to Michael B.

Even tho' the axle-to-crown distance is about 25mm more than on the XACD fork, this has no discernible effect on the ride except to make the bike more stable, less quick to fall in to corners, more like a Ducati if you see what I mean. As an ex-duke owner I'm happy with the new geometry.

I took the XACD fork to Eglinton Engineering in Magill, Adelaide, where the helpful and friendly Ian put it on a straight flat plate and put a square up against the brake tabs. Instantly it was apparent that the brake tabs on the fork were the problem: not quite in the same plane as the disc. By eye I couldn't see this at all. I don't claim to have the best eyes.

The fork will be going back to XACD. I await their response with interest.

Peter

[MichaelB]

Great result in the end, and glad I could help (although it wasn't much).

Be interesting to see the response/resolution from XACD

Cheers

Michael B

[Nobody]

I fitted the Kinesis DC19 fork and the new organic pads that c r c sent under warranty. Result:

1. Brakes instantly align and adjust up perfectly (what a joy).
2. Braking is powerful and dead quiet, although I've yet to fully bed in the pads.

A huge improvement. Thanks again to Michael B.

Even tho' the axle-to-crown distance is about 25mm more than on the XACD fork, this has no discernible effect on the ride except to make the bike more stable, less quick to fall in to corners, more like a Ducati if you see what I mean. As an ex-duke owner I'm happy with the new geometry.

I took the XACD fork to Eglinton Engineering in Magill, Adelaide, where the helpful and friendly Ian put it on a straight flat plate and put a square up against the brake tabs. Instantly it was apparent that the brake tabs on the fork were the problem: not quite in the same plane as the disc. By eye I couldn't see this at all. I don't claim to have the best eyes.

The fork will be going back to XACD. I await their response with interest.

Peter

It's a BB7 out of the box, standard pads and rotor. Very noisy in the dry and wet.

Maybe have a look at the possible solutions in this MTBR article. I will add that maybe your pads could be glazed and it may be worth trying to bed them in again. My standard setup is almost silent now at speed and only gets a bit noisy when going slowly. It used to always squeal (to the point of being embarrassing) before I went to a big hill and bedded it in properly.

Since you are using a XACD Ti fork with the shims/washers, it may worth swapping the fork to see if the fork is the problem. Ti having a bit more flex may be introducing the movement to allow the squealing. That is the same reason I believe my steel forks (on both bikes) are a bit noisier at low speed.

Bed them in again????????? What do you mean by that? I followed the instructions from Avid to bed them in. As for swapping the fork, I don't think so.

viewtopic.php?f=34&t=31034&start=50

[cooperplace]

yeah, I've been watching this topic all along with much interest.

[baabaa]

Good result Peter.
I think you will find that now you have the calipers sitting on the fork as they should, all that past frustration and fiddling will help.
You must know them inside out. Fine tuning on a dark moonless night will not be a problem for you.

I use three wheel sets (and a set of pads for each set) for two bikes and to swap out wheels, pads and reset my calipers and then fine tune pads and cable/ (dropbar)lever play normally takes less than five minutes.

Must you really need to send the fork back? If so ask XACD to pay for the postage, they may just send you a new fork instead of the cost back to them plus the new fork + postage.

[cooperplace]

hi BaaBaa,

I don't really need to send the fork back because I now have a nice Ti bike with a CF fork, works well, and a great Ti paperweight. I really liked the Ti fork, it gave such a nice ride. I think I will send it back, tho, and ask them to pay all the postage.

I have to say the people on this forum have been very helpful and offered lots of suggestions that ultimately enabled the fix.

And yes, i now know the BB7 _too_ well.

[cooperplace]

kinesis cf fork now fitted, new brake pads bedded in, and it is all great. extra height at front makes bugger-all difference to the bike, except that the front end seems more stable. Brakes are quiet and powerful.

I sent the XACD fork back to them today, we'll see how it goes.

Peter