Installing Avid BB7s on a commuter... anything I should know?

[Pegleg]

Just ordered BB7's and Avid levers to replace the shitty Tektro mechanical discs that came on my Giant Seek 2 commuting bike. I've never put new brakes on a bike before, but it doesn't seem that hard (esp. replacing mech. discs with mech. discs). Wondering if I can re-use the cables currently on there or if I need to buy new, and also whether there's anything else I ought to know before jumping in.

Thanks.

[toast2266]

Pretty straight forward. Reuse the cables unless they're mangled, although if they're cheap cables, the brakes will feel better if you buy nice housing. Align the calipers so that the rotor is as close to the "moving" pad as possible.

[fatkid]

toast- not so much.
youll be psyched if you get new cables, 2 bucks each is pretty good... and most important you want to align the rotor closest to the fixed pad in the caliper. if you align it to the moving one, the rotor will flex and bend before it contacts the fixed one and your brake will be mushy and not stop well.

[Pegleg]

Excellent, thanks for the tips. Just realized that Avid has a YouTube video showing how to do the install - that ought to help.

[toast2266]

toast- not so much.
youll be psyched if you get new cables, 2 bucks each is pretty good... and most important you want to align the rotor closest to the fixed pad in the caliper. if you align it to the moving one, the rotor will flex and bend before it contacts the fixed one and your brake will be mushy and not stop well.

Nope, at least as to the alignment (everything feels better with new cables, but I'm cheap). If you align it next to the fixed pad, then as soon as the pad wears, you'll be pushing the rotor into the caliper body, which is bad. Setting it next to the moving pad causes the rotor to flex ~ 1mm. It makes a negligible difference as far as the rotor is concerned, and if you think that makes you brake feel mushy, then you're doing something else wrong, in addition to setting up your caliper incorrectly. Per avid instructions, "the avid caliper design is to have the inner pad-to-rotor gap about twice as large on the outer pad-to-rotor gap."

Here's a picture of how it should be (courtesy of park tools):

[Dickeymotto]

toast- not so much.
youll be psyched if you get new cables, 2 bucks each is pretty good... and most important you want to align the rotor closest to the fixed pad in the caliper. if you align it to the moving one, the rotor will flex and bend before it contacts the fixed one and your brake will be mushy and not stop well.

This. The rotor goes as close to the stationary pad as possible.

[toast2266]

This. The rotor goes as close to the stationary pad as possible.

*sigh* No.

skip to 1:40




edit to add: you can have the rotor as close to the stationary pad as you can get it, as long as the caliper is aligned so that the rotor is close to the non-moving side of the caliper. The point isn't to have the rotor close to the moving pad but rather to have it far away from the stationary side of the caliper body.

[fatkid]

teh interwebz is on your side, but im stoked to be riding my brake setup rather than yours. good luck with that one!

[Dickeymotto]

teh interwebz is on your side, but im stoked to be riding my brake setup rather than yours. good luck with that one!

Indeed, I've been setting them up this way for years and have always been blown away at how good they work. I always lube up the cable housing with Phil Wood as well. Set up like that, I prefer them to lower end hydraulics hands down.

I do recognize that you are right though. Setting the rotor closer to the moving pad probably makes them a lot less grabby (is that a word?), but that is how I like them to feel. It compensates for the difference in power vs a hydraulic brake. To each their own I suppose.

[Pegleg]

Update: I got the front caliper, rotor and lever installed last night following the instructions precisely, and everything appeared to be working OK on the bike stand. But when I rode to work this morning, the brake has zero stopping power - it engages, but it feels like the pads are made of felt and the wheel just keeps rolling. Is this part of the normal break-in period? I had heard it would squeal, but this is just incredibly mushy. Also, it seems to be rubbing just slightly, but if I back the pads out one click at a time until it stops, I have to pull too hard to engage. What am I doing wrong here?

[bbense]

Update: I got the front caliper, rotor and lever installed last night following the instructions precisely, and everything appeared to be working OK on the bike stand. But when I rode to work this morning, the brake has zero stopping power - it engages, but it feels like the pads are made of felt and the wheel just keeps rolling. Is this part of the normal break-in period? I had heard it would squeal, but this is just incredibly mushy. Also, it seems to be rubbing just slightly, but if I back the pads out one click at a time until it stops, I have to pull too hard to engage. What am I doing wrong here?

BB7's come in two versions. One for Road levers and one for V-Brake levers. Kinda sounds like you've got the wrong version for your levers. Mine worked just fine out of the box. The other thing to check for is any slop in the cable housing. You did buy a "pre-stretched" brake cable right?

[Pegleg]

Used the old cables (they're not that old - only had the bike for a few months and it's a commuter so I don't even use the brakes that much), so they should be plenty pre-stretched. I'm pretty sure I got the MTB version and the Avid Speed Dial 7 levers, which are supposed to work together fine. I tried cleaning the rotor and the pads with alcohol and a little sandpaper; not much difference. Very weird.

[canyonrider]

Try tightening up the cables a bit, sounds like they might not be adequately tensioned. Also make sure you've properly adjusted the speed dial function on the lever, that will impact lever mushiness.

[XXX-er]

If you follow the instructions the brake should work fine altho step 4 in this link to the instructions may be unclear but basically you adj the slack out of the cable so there is minimum slop between the adjuster on the brake lever and the metal ferrel of the cable housing and then adjust the pad clearance with the red knobs

http://www.sram.com/sites/default/fi...15-008-000.pdf

and the correct caliper should have " bb7 mtn " etched on it

http://www.sram.com/avid/products/bb...cal-disk-brake

I used the same cable & housing for >2 yrs and it was fine

[Pegleg]

The cables definitely don't have any slack in them - as soon as I start pulling on the lever at all, the caliper starts moving. I did try re-aligning the caliper, and that seemed to help some - I was able to get the pads in tighter without rubbing. I'll keep messing with the details and see if I can get it working better, and will report back.