jethro00

We have disc brakes on our daVinci Grand Junction. With help from this forum, I have become competent at most maintenance tasks. While I can adjust the brakes, I have not mastered them. So, we took the bike to a LBS to adjust the rear brake properly after it got way out of adjustment on a long ride. When we got it back, it was rubbing. They adjusted it again. When we got it back, it did not rub, but the rear brake had little to no grip, even though the gaps were okay. So, we got new brake pads recommended for our Avid BB7 brake (AVID Organic Bicycle Disc Brake Pad Set with aluminum back plate). I could not get the new pads to click into place and the piston came out. So, we took it back to the LBS to install the new pads. It now has plenty of grip and stops just fine. But, it makes a loud noise when we brake and vibrates so much that we feel a tingly sensation in our saddles. Now, I'm not saying the tingling is entirely unpleasant , but I have to come off the saddle to use the rear brake. I have researched online for a fix, but haven't found anything so far. I hate to go back to the LBS again, but the noise and tingling need to stop. Any suggestions?

Leisesturm

I have two bikes with mechanical discs but I have not had to learn how to change pads yet. But it sounds to me like the pads were put in incorrectly. I would take it back to the LBS. Sorry, but they should do this kind of work better than you can do it yourself. It sounds, though, like this particular LBS maybe needs to be kicked to the curb. Is there a bike co-op near you? Co-op's in my experience with them have more conscientious techs and they do better quality work for far less money and often while you wait than any LBS I know.

JoeShellharbour

When we ride our Cannondale after a long break (say 6 weeks) often the brakes vibrate and squeel , I find if I give the brakes a Heavy application for say 20 seconda on 20 off, a few times down hill it goes away.
I also have found the same on my Giant Solo bike and the same brake trick stops the screem
Although the screem is better than the bell to wake up pedestrians who ignore the bell so not all bad!
Joe

jethro00

Joe, that might work where you are, but where we live there are no hills that take 20 seconds to traverse . It's all flat around here. The only "hills" we get to descend are when we come down the levee path from the top of the levee. I haven't timed that, but I'm thinking maybe 10 seconds at most. I could suggest to my stoker that we go down and back up a few times. But, it's going to be 40F in the morning and she might be less than enthusiastic over that idea. Also, turning the tandem around at the top and bottom of the levee path would not be easy.

Joint Venture

New disc brake pads need “bedded in” for sure, but you don’t need a hill to do it (although that makes it easier!). First make sure your rotors are CLEAN - no grease, oil or even skin oils. Automotive brake cleaner works well for this. Sprint up to your top speed and then apply the brakes HARD, but don’t lock them up. Keep pedaling, if you can, against the braking to make the pads work a little harder. Do it 10, 15 or even 20 times in a row. You can bed in the front pads pretty well without having your stoker aboard, but you may need her for the rear as the rear brake may skid the wheel too easily otherwise. The bedding in process will quiet your brakes and improve braking performance by having the pads and rotors wear in together.

Changing the pads on an Avid BB7 is a little tricky because of the funky spring clip holding the pads. I learned how watching some YouTube videos. That said, the BB7’s work quite well on both da Vinci tandems we have owned.

jethro00

H-m-m-m, I use a spray bottle of oil on the chains. I wonder if some spray got on the rotor. I have a chain degreaser and will use that on the rotor. Then, we'll try your suggestion about riding and braking. We get out early enough in the morning when it's unlikely someone will come up behind us, particularly as cold as it is in the mornings now.

JoeShellharbour

Wow we have to travel 100km inland to get any flat land we just get hils and plenty of them.
we hit the bottom of the hils at )30kmh and often down to around 10kmh as we crest..- no spare gears we use the lot!
But we go down thw other side at > 40kmh
Good luck with the rotor clean and bedding in
Regards
Joe

Chilepines

I'm curious what others will say but I would not use chain degreaser on a brake rotor. Brake cleaner is alcohol and I think the only thing you should allow to touch the pads. Once they get contaminated you will have a hard time salvaging them.
In addition to a good cleaning with alcohol, it can sometimes help to us fine sandpaper on rotors to get them to stop squealing. Sometimes on a ride I'll actually throw fine sand into the brakes and it works!

motochick 

Have you had your disc mounts made flat ? It would need to be done by someone who has the Park Tool disc mount facing tool. I have one and not one bike I have used it on was flat from the factory. Once the mounts are flat, it makes it harder for them to get out of adjustment.

jethro00

I used the degreaser to wipe down the rotors before Chilepines suggested using alcohol. The next day, I used alcohol to wipe down the rotors. If nothing else, we now have very clean rotors We are still getting tingling in our saddles and a foghorn sound if I depress the rear brake more than a little bit. We have tried getting up to speed and braking over and over as suggested above.

fooferdoggie 

yes the degreaser can be bad and really clog things up depending. I will use some of the finish line spray degreaser if things are really bad but afterwards I will have to bed the pads again as it strips everything. I usually just use it now after I bleed the breaks without the pads installed. alcohol in a spray bottle works well.

jethro00

Motochick, I have not had the disc mounts made flat. I see that the Park Tool disc mount facing tool costs $500+. Looks like our disc mounts may stay as they are

merlinextraligh

this is one of those jobs that even if you do your maintenance that it pays to leave to the LBS.

Expensive tool, rarely used is a good reason to pay the bike shop.

motochick 

Ya, it would be crazy to buy one but it came in my master tool kit so….

Alcanbrad

Assuming you have same size rotors, try swapping rotors and pads front to back. If the undesirable behavior moves to the front, replace pads and rotor, if it stays at the rear, you got something else going on - calipers, mount, chain/seat stay. Don’t touch or clean the rotors, just swap both pads and rotors together and see what you get.

jethro00

I don't think I am up for swapping the rotors and pads from rear to front. I could not get the new pads to click into place and the piston came out when I tried to install new rear pads. I imagine with enough time and YouTube videos I could get the hang of it. But, . . .
The frustrating part is that we've taken the tandem to a good size LBS 3 times to work on the rear brake, and it's still not as it should be.

Yamato72

Make sure the rotors are true so that you can adjust the inner shoe as close as possible to the rotor without introducing an annoying intermittent rub-rub-rub. The inner shoe is fixed relative to the outer shoe, so the BB7s will flex the rotor inward when the brakes are applied; you'll get the best feel and power only when the above steps are taken. Once that's done you can adjust the outer shoe as close as possible to the rotor, again without rubbing. BB7s can be tuned to be very, very smooth and strong but it takes practice (make sure you have a torx screwdriver for adjusting the shoes).

For cleaning I used to use acetone but my rotors would start squeaking after only a couple miles. Now I use denatured alcohol to clean the pads and rotors and it helps a lot. When the pads get very dirty I clean them with 320 grit sandpaper on a flat surface. I've tried both organic and semi-metallic pads and they both squealed until I switched to the denatured alcohol. I figured the acetone must leave some trace residue on the rotors. I still manually clean my pads and rotors every 100 miles or so. Be sure to never touch the pads or rotor surfaces with your fingers - it will introduce oils and everything off the road will be attracted to it.

One other thing I did for stopping power & feel was change out the brake housings to Jagwire compressionless. It made a difference too.

jethro00

Yamato72, I have denatured alcohol. So, I'll clean the rotors and pads with that. It's running smoothly now and with good stopping power. But, it still sounds like a fog horn when the rear brake is applied lightly and it also still causes a vibration/tingling sensation on both saddles.

jccaclimber

If nothing else, it sounds like you should take up a policy of test riding repairs before taking the bike home from the LBS, even if it’s a different one.

LV2TNDM

Depends on the denatured alcohol being used. 90% Isopropyl alcohol is preferred over 70%, if you can choose. Sounds like the rotors were not as clean as they should have been and the pads got contaminated. Clean the pads with the alcohol. Once dry, then sand them, as mentioned above, with fine grit on a flat surface. Then re-bed the pads to the rotors and this SHOULD resolve the issue. 10 hard brake applications per brake from speed - but not to a full stop. This should get them performing as intended.

Otherwise, caliper alignment MIGHT be the issue. But probably not. But make sure they're tight. I'd make sure the rotor is torqued properly to the hub. And then check the hub for bearing play. Check the replaceable derailleur hanger/dropout also to be sure it's tight, square and plumb. And issue there could cause the brakes to create a vibration that would transmit through the bike - and saddles!

jethro00

Thanks for the suggestions. Unfortunately, test riding the bike before taking it home from the LBS is not an option for us. I can't go to pick it up and the LBS is under-staffed these days and not likely to be able to let someone take my stoker for a test ride and she can't ride it on her own. We're still getting the fog horn sound and vibration through the saddles. S-o-o-o, I'll work onLV2TNDM's suggestions this weekend. It's been to the LBS 3 times just to work on the rear brake. It's one of the biggest LBS's in town. I have to believe they would have fixed it if they could figure out how.