Need help with brakes, bb7s w/180mm g2

[Tigris99]

SO I got a set of Avid bb7s and 180mm g2s for my 29er. Been doing some paved riding around here as weather permits, only total about 10miles since I put brakes on last week (snowmobiles own paved trails when there is snow so riding them can be a PITA)

As of right now, back brakes are INSANELY TOUCHY. I got Speed Dial 7 levers to go with them and have the rear turned as soft as possible now. Not only touchy but they make that annoying howling noise. I even backed both pads off a click to try and at least get some of the bite outta them, seeming I need to back off more.

Fronts on the other hand suck for braking power. they work but not near enough there with levers turned all the way up.

What did I do wrong?
How do I fix it?

I did lightly sand front brakes so they can start over not sure what I did wrong over the rears, guessing I had front set too tight to start with (only difference I know of in set up from front and back). As for the backs not sure what to do there, howls similar to car brakes if you get them too hot and glaze them.

Anyone that can help I would greatly appreciate it so I can get these set right before hitting the trails again.

[Byke Dood]

This might help


http://www.youtube.com/watch?v=x1kezXQVnLY

[SweetSVT99]

As far as stopping power: If they are new, or if the pads/rotors are a mix of new/used, have been used with another set, etc, the brakes will need to be bed in. Some people have specific bedding (or breaking in) procedures they follow, I just go out and ride making sure to get on the brakes hard a few times. Eventually the stopping power will increase, usually doesn't take long and obviously the more you use your brakes the faster it'll happen. Also make sure that you have the correct caliper adapters, and the rotor fits into the caliper with as little top clearance as possible, without rubbing.

Howling can be a number of things: Contaminates on the pad or rotor, poor adjustment and cheap pad material are the most common, mixed in with poor rotor design at times as well.

[jimithng23]

Avid brakes have a history of this howling problem, and it's never been traced to one particular thing causing it but rather, multiple components.

I had a set of Elixir CR's and the rear 185 rotor would howl and resonate through my entire frame and into the handlebars. It was ridiculously annoying. I worked with the shop where I bought the brakes and Avid sent me a new rotor and pads - worked like a charm.

Does this mean a new rotor and pads will fix your issue? Hard to say...check mtbr in the Brakes Forum and you'll see the "Avid Turkey Warble" thread - it has thousands of posts.

Good luck!

[Tigris99]

Actually I used that exact video had it playing on my computer as I was installing them (bikes stay in basement by my computers while it was so cold outside). Thnx I should have asked when i got the brake took me 45mi.s of digging to find that bid.

Ok so basically just haven't used my fronts enough it seems cause I use way more rear than front (old habit from v brakes) . I'll work on that just using fronts to get them bedded thnx.

Noise, I had no idea it was an avid issue. I don't really have fund atm to replace rotors (i can take the polishk off to try new pads) what's a good all around pad that u guys would recommend cause if not too much I can sqeeze the funds in for them. Did a lot of other work to the marlin so bike funds are 0 atm.

Thnx

[Tigris99]

Ok did some digging in MTBR about the noise issues and I noticed the same thing that seems to be the issue, the sharp edges on the vents from rotors being stamped.... tried wiping rotors down and kept trying to eat the blue shop towel..... Really dont wanna take the dang things off and smooth it out so going to try and get by with doing it carefully on the wheels (off the bike of course). Cleaning the rotor with brake clean seemed to kill the noise for the moment though.

Guess when I can afford it, rotors are next on the list. Could use some advise from you 29er guys on rotors pads that arent insanely expensive but work year around for out here.

[jJohnson]

You don't necessarily need to replace the rotors. Take rubbing alcohol and clean them nice and good. Ride them, bed the pads, there's a top layer of the pads that needs to wear off. It may go away naturally. The sound is just annoying, it doesn't affect performance at all. I have BB7's on my Voodoo and my fat bike. They're pretty simple to work on once you get the hang of it, but have a learning curve. They're the best mechanical disc brakes on the market, though. If you have rub, check to see that the rotors aren't bent at all. That happens a lot, especially out of the box they might have a small tweak in them. Park makes a break rotor bending tool.

[Tigris99]

actually i know they BOTH have a slight bend. That noise i know, this one is a howling almost like v brakes do sometimes just deeper tone. hopefully the cleaning and working on bedding will square it away if the rotors/pads are ok once I get them bedded. mech brakss are new to me and the ones that came on the bike bedded really easy no noise (tektro mechs) I just needed more "ass" behind my brakes to stop cause of my size. Guess maybe over thinking this lol (no suprise there) thnx

[DH001]

Things to try:

Plan A:

Remove any oils from the rotors with an adequate solvent. Acetone, methanol, or brake cleaner are good choices but don't get them near your bearings or the grease may be compromised. Apply the solvent to a clean rag and use that to wipe down the rotors.

Immediately repeat burn-in procedure for your pads (10-15 decelerations to walking pace from 15-20mph).

Plan B:

Remove the rotor from the hub. Get a sheet of fine sandpaper (500+ grit) and lay it on a flat surface. Rub the rotor on the sheet of sandpaper in a circular motion until the surface has an even distribution of micro scratches on the braking area. Repeat for the other side. This will slightly roughen the rotor surface and will help it mate with the pads. This micro texture helps the pad material bond evenly to the rotor during the burn in period. Slightly sanding the pad surface (same process as with the rotor) before this would be helpful but isn't necessary.

You will need to repeat the burn-in procedure for the brake pads after this process also.

I doubt stamped edges of the rotors are the culprit. I think most rotors are laser cut and won't have flashing in the first place. Any quality rotor would also go through a surface grinding process before shipment which would remove any burs (this is done to help with pad burn-in).

I also doubt the noise is being caused by a rotor that is slightly out of true. The howling noise has a frequency that is completely out of sync with the slow rotation of the rotor. When I have had bent rotors, it was always more of a ticking+grinding noise.

As far as I can tell, the howling noise is generated by resonance in the rotor/pad system; the rotor essentially becomes a tuning fork under certain conditions. The trigger is likely small variations in the braking force at the pad/rotor interface caused by the cutouts in the braking surface or an uneven distribution of pad glazing on the rotor. These small force variations are likely happening at one of the rotors harmonic frequencies and causing resonance. If you can't get any of the previous suggestions to work, you may have to try a different rotor/pad mash-up to change the harmonics of the system.

[jJohnson]

actually i know they BOTH have a slight bend. That noise i know, this one is a howling almost like v brakes do sometimes just deeper tone. hopefully the cleaning and working on bedding will square it away if the rotors/pads are ok once I get them bedded. mech brakss are new to me and the ones that came on the bike bedded really easy no noise (tektro mechs) I just needed more "ass" behind my brakes to stop cause of my size. Guess maybe over thinking this lol (no suprise there) thnx

The howling sound is most definitely not from a bent rotor. I usually get howling when the rotors are wet and there's crap on them. Try all other suggestions, and if that doesn't work then live with it until you can afford new rotors. Also try to put some lube (like Park grease) on the back side of the pads. I forgot about that. I've had good luck with that, but make sure not to get any on the pad surface.

Ironically, the v-brakes on my Rocky Mountain are quiet in all conditions.

[Tigris99]

Didnt think about lubing the pad backings...have to add that to the list too. Thnx

[Tigris99]

Ok so these arent the "most awesome rotor" but reveiws I have found rate them way higher than the avid g2s!!! Actually overall pretty good reveiws, just these are a couple year old design (so is bb7s with g2s ) Found them on ebay total $30 for a pair shipped! Good night in tips tonight so I went for it. I let you know how these do when i get them in next week. And yes I even got the version with white centers hehe

[Tigris99]

OK so I got new rotors in and this time cleaned EVERYTHING properly after install just to make sure.

Front Situation remained, insane noise in the rear- only mild now and going away.

FRONT....so started looking close something wasnt right AT ALL. Braking is a bit better than before rotor change but still weak....

SO I started looking closely at the caliper and its movement, omg I FOUND THE DAMN PROBLEM. The adjuster plate that is against the pad that moves, sits inside the main piston, was coming out at a funny angle. Took pads out and it flopped around inside the caliper and a bit of shaking it FELL OUT!!! WTF??? so I looked and shook, little retainer ring fell out....FACTORY ASSEMBLY SCREW UP!!! put the retainer on the plate properly, shoved it back in the piston (yes had to split the caliper to do all this) and put everything back together.

AND HOLY MOTHER OF GOD, HUGE DIFFERENCE, brakes work GOOD and they arent even bedded barely yet!!!!!!!

Thnx for the help guys, at the very least all this reading and help I have learned fully how these things are supposed to work when all done properly and how to fix when they arent.

THNX MUCH!

And that being said, had to go play today, so hit the paved path in Clinton on Riverfront (path goes right by one LBS so put SIS '13 fliers in rack bag and dropped off when I got that far) and used the hills to work on bedding. Made for a VERY HAPPY END OF MY DAY after working 12 hrs yesturday and being at wits end with the front brakes. Even tried to take the detour to the island, didnt make it very far (not even the 15yrds to the trees) before i got stuck and more or less fell in the snow. Was fun, but damn need a fatty for snow!



PS: Learned something else today... 45-50 psi on tires good and still roles fast on pavement!!! 65 psi BAD!!! I felt like i had been beat and battered by the time I got back to my truck. Paved path needs some tlc there atm cause cracks the are as long as path width and have created hard sudden dips you cant avoid. Im 75 lbs lighter now, dont need 65 psi to hold the tires up for fast on pavement apparently hehe.