[mandown]

I recently got a 2003 BB7 and I have been trying to dial it in. I seem to be getting some clicking from the drive train when I am in the lowest 3 cogs of my 9 speed cassette (it happens in the higher gears too, but not as much). It sounds like the chain is binding and feels like there is a little skip that goes along with the click, but I have not been able to isolate the problem with the bike up on the stand.

I am guessing it could be chainguide related. I have an Evil SRS on there now. I have a feeling that it could be due to the fact that the Evil has a toothed pulley (vs the smooth rollers on an MRP). I think the driveline of the chain is angled too far and it pulls on the teeth of the guide pulley. I recently removed some links from the chain to shorten it a bit, but I may have gone too far. Any advice on how to set the chain length? Any thoughts on the mystery noise?

 

[ssaddict]

Sounds like your chain is too short, but it could be other things.

How do you have your guide setup/angled?

Its pretty critical on a BB7 because of the high roller, but I have a similar setup on my BCD/e13 and it's flawless.

Are your roller and chainring lined up properly? If not you need to space it out so they are.

The best way to do chain length is to take off the shock spring, shift into the lowest gear, and see how far the der. stretches. Its a PITA but it works. Honestly you probably have it pretty close if you haven't ripped your der. off yet while riding, so just add a link (i like to use SRAM quicklinks for just this purpose) and see if the noise goes away.

Or the really simple solution, you could just have your der. adjusted improperly and need to tune it.

 

[DHracer1067]

well one time my drive train was "clicking" because i bent the cage on my derailer. the chain would snap down into the pully. like the side of the chain got on top of the tooth then snapped down onto it. took me a long time to figure it out but thats what it was.

 

[buildyourown]

I would check that the chain line of the front chainring and the chain guide pulleys and the "BB7 Pulley" all line up prefectly. I know I had to shim my mrp pulleys out a bit to make things run smooth. Does it back pedal smoothly?

 

[mandown]

the bb7 high pulley is now lined up near perfect with the chainring. it was offline by a bit and it bent the supporting bolt and took a chunk out of my frame. i have since fixed this

side rant - i took the bike to my local shop to handle the headset and bottom bracket instal. they told me that the chainline to the high pulley was off and needed a few shims. i let them do it. when they were done it looked like the chainline was off a bit, but i figured they had checked it and worked on it, so it was the best it could be. i then bent the support bolt for the pulley on the first day of big mountain riding. when i took things apart and fixed it myself, i removed the shims the bike shop put in, and the chainline was near perfect. i was pissed that they messed it up and it cost me a chunk of frame. if they had not shimmed the pulley, the chainline would have been straight and the support bolt would probably not have bent.

the lbs did say that i needed a new rear der. when i gave it to them to press in the headset. maybe it is time to give that a shot. i do have an extra that i could use.

and yes, the thing backpedals fine.

thanks for the input. anyone else?

 

[ChrisRobin]

Yeah, check to see that the chain isn't binding between the frame pulley and the swingarm pivot. On some frames, the little cog in the pulley isn't filed down enough (it's ramped) and in certain gears, the chain tried to jump off and gets stuck up against the underside of the pivot. Hard to describe.

 

[mandown]

christopher robin, you did a great job of explaning it. i thought that the clearance looked a bit tight. maybe the removal of the shims some how "activated" the jump on the frame pulley. i was too busy looking at the evil pulley because that is where if "felt" like it was.

to revisit the question on chain length. I think that due to the way the pulleys are set up and the the high location of the chainguide pulley you should be able to run a pretty short chain on the bb7. the rear der will just have the cage sticking straight our toward the bottom bracket in the big gears. i was watching the chainline as i bounced on the bike and compressed the suspension. it looks like the chain length stays farily constant through the first part of the travel (the der did not move much). i see two big problems though. 1 - the chainlength may change more than i have estimated, particularly when it gets deeper into the travel, and the der could be ripped off. 2 - each chain link has a given amount of lateral flex. the more links between the big ring and the der cage, the more total lateral flex you can have without stressing the chain. more links also means more length and a less extreme angle in the chainline from the der cage to the big ring. however too many links means too long a chain swinging around (and precious grams of mass - j/k). where is the trade off between having the right angle and lateral flex vs. having a long sloppy stretch of chain haning around.

 

[ChrisRobin]

There's a crap load of chain stretch with that rearward axle path.

When I had my 2003 BB7 (briefly mind you), I had it setup with an E13 guide. In all honesty, all I did was line up the upper chainguide 'slider' with the BB7 pulley so the chain was perfectly straight. That's all. I didn't change any shims anywhere in the frame. My pulley never skipped but my buddy's did in the lower gears (big cogs). I say return everything to stock and start over.

 

[mandown]

Last night I went over everything. I took the shims out from the high pulley bolt (the ones the shop put in) and now my chainline is straight from the chainring to the high pulley. I am still getting the skip on the high pulley in the bigger cogs on the cassette. The skip is coming from the high pulley (not the Evil pulley as I once thought).

I can see the ramp in the high pulley teeth. I am thinking about replacing it, but not sure how to go about it. I removed the 3 bolts that hold the pulley sandwiched together. It looks like there is a single cog from a rear cassette on there, but I am not sure how to get it off I could see the ramping on the teeth, which leads me to believe that is the probelem, or at least part of it. Wondering if it is an 8spd cog. That might be a problem if I am running a 9 spd set up. Maybe i should put my 8 spd stuff on it and see if things change.

Lemme know your thoughts Chris.

 

[ChrisRobin]

Last night I went over everything. I took the shims out from the high pulley bolt (the ones the shop put in) and now my chainline is straight from the chainring to the high pulley. I am still getting the skip on the high pulley in the bigger cogs on the cassette. The skip is coming from the high pulley (not the Evil pulley as I once thought).

I can see the ramp in the high pulley teeth. I am thinking about replacing it, but not sure how to go about it. I removed the 3 bolts that hold the pulley sandwiched together. It looks like there is a single cog from a rear cassette on there, but I am not sure how to get it off I could see the ramping on the teeth, which leads me to believe that is the probelem, or at least part of it. Wondering if it is an 8spd cog. That might be a problem if I am running a 9 spd set up. Maybe i should put my 8 spd stuff on it and see if things change.

Lemme know your thoughts Chris.

Replacing it won't do any good. From the factory, Balfa uses regular cogs and grinds them down themselves. I guess sometimes they don't grind enough. Take the pulley apart and take a file to it or put it to a grinder. That should do it.

 

[ssaddict]

Replacing it won't do any good. From the factory, Balfa uses regular cogs and grinds them down themselves. I guess sometimes they don't grind enough. Take the pulley apart and take a file to it or put it to a grinder. That should do it.

Is that really what they do? Sh*t, I can almost guarantee that is where your problem is coming from. Alex of BCD uses Chris King single speed cogs for his upper roller. They have no ramps and tall teeth and will never skip.

I had very similar problems with one of my single speed bikes a few years back. It kept throwing chains cause the ramps were pushing the chain off. I ground off all the ramps with a dremel and that worked pretty good, but switching to a King Cog was the real answer cause the profile of the teeth was different.

 

[buildyourown]

There's a crap load of chain stretch with that rearward axle path.

No there isn't. That is what the pulley is for. There is very little chain grow on the BB7 compared to other single pivots like the super8

 

[ChrisRobin]

Is that really what they do? Sh*t, I can almost guarantee that is where your problem is coming from.

That's exactly what they do...when you take it apart, all you see is a cog that's been taken to a grinder.

 

[mandown]

How do you get the cog off? I would replace it with a king cog that is rampless, but I cannot figure out how to get that bugger off. It looks like it is in there good.

Help?

 

[ChrisRobin]

No there isn't. That is what the pulley is for. There is very little chain grow on the BB7 compared to other single pivots like the super8

oh yeah! my mistake

 

[ChrisRobin]

How do you get the cog off? I would replace it with a king cog that is rampless, but I cannot figure out how to get that bugger off. It looks like it is in there good.

Help?

I'm not sure...I didn't have this problem when I had my BB7. Aren't there 3 bolts holding it together. I really don't remember.

 

[mandown]

i pulled the three bolts, but that cog looks like it is on there good and tight. i tried to pull it off, but hand strength alone won't do it.

anyone else got a bright idea?

 

[ChrisRobin]

Use a flat head screwdriver

 

[mandown]

thanks

i will give'r tonight.