hey all,

I've read up on sheldonbrown, and the park tool website, but I've either misdiagnosed the issue, or fixed it incorrectly:
on the rear gears, when upshifting (e.g., from largest/easiest sprocket to 2nd largest/easiest), the chain kind of "hops" from one sprocket to the next -- like it is lifted up too far, and then slams down on the next gear. This creates a slight delay in the shift, and obviously throws off my pedaling stroke. Conversely, there is a *slight* struggle when downshifting (e.g., from smallest/hardest sprocket to 2nd smallest/hardest) -- not as apparent, but certainly noticeable.

So far, based on what I've read, I've cleaned the cables and housing, and tightened the cable tension by loosening the barrel adjusters -- a small amount at first, then about 2 full turns. This has not improved the situation. So is something more than cable tension adjustment required?

thanks for any advice...

It sounds like you have indexed shifters, in which case you need to understand a little more about what happens when you turn the barrel adjusters. You're not adjusting the cable tension (unless you're in the biggest cog already and you're tightening the RD against the limit screw), you're just adjusting the effective length of the cable and moving the RD slightly to one direction or the other. For indexed shifting to work properly the RD needs to be pretty much aligned with the cog when it's supposed to be in the gear. This is a rather finicky adjustment in practice, it takes patience and pro wrenches know not to do it with the customer standing right there as it can take time and profanity. If you're turned your adjusters two turns, they're already a mile off and you pretty much need to start over. The park and sheldon guides are good for this. Once you've done this you can see if you're still having a problem. Rough shifting can be a bad index adjustment, or it can also be cause by a worn cassette and chain. You want to replace both at once, as they wear in together.

Yep, sorry -- should've mentioned indexed shifters.

I'm not sure what you mean by "the RD needs to be pretty much aligned with the cog when it's supposed to be in the gear." -- the derailer should be lined up vertically beneath whatever sprocket the chain is currently on?

p.s. -- I was adjusting (loosening) the barrels based on the following from the sheldon site -- did I mis-interpret?:
"* Shifting to larger sprockets is accomplished by tightening the cable;
if such shifts are slow, the cable is not tight enough--
turn the barrel counterclockwise to tighten it.
* Shifting to smaller sprockets is accomplished by loosening the cable;
if such shifts are too slow, the cable is not loose enough--
turn the barrel clockwise to loosen it."


thanks for the response..

Ok, I think you understand, but here's a slightly clearer explanation. The shifter (as in the part on the handlebar) pulls exactly the right amount of cable to move the RD 1 cog's worth for every click. The only tension on this cable is what the spring in the RD provides. The barrel adjuster just lengthens or shortens the amount of cable in between the shifter and the RD; you're not adjusting tension at all, just location. "Tighter" and "looser" seem like appropriate terms because you're turning threaded gizmos and one direction is against resistance and the other isn't, but it confuses the issue by making you think you're playing with cable tension and not length. The goal is simply to align the places where the RD stops with the positions of the cogs. Again, this is a pretty fine adjustment, 1/2 a turn can be the difference between good and useless, and 1/4 turn is the difference between OK and awesome. Complicating this is the fact that the upper pulley on most RD's "floats" a little to compensate for slight misadjustment. It's also possible to screw the barrel adjusters down so far that you can't even get into the top or bottom gear, the shifter just doesn't have the cable to give you or can't pull another full interval as the case may be.

Another issue to check: "B" screw adjustment. Your jockey wheel may be too close to the cogs.

and if all else fails: derailleur hanger alignment may be a little out of whack.

Another cause may be a slightly bent dérailleur hanger. The only way to cheek this is with a shop tool. Probably not something that is in a home mechanics tool box. Take the bike to your LBS and ask them to check the alignment.

Makes perfect sense. Thanks much.

Thanks for the other responses also -- I'll check B screw adjustment, and failing that, take it to LBS.


cheers,

I tried and tried to figure out "loosen if it doesn't downshift", etc, but it just wasn't working for me (I'd later learn why ).

From what I learned last night --

https://www.bikeforums.net/bicycle-mechanics/356374-plucking-my-own-little-epiphany-but-twist.html#post5512365

I'd try using the barrel adjusters to set the cable tension just enough to get rid of any slack.

If it's too tight, it'll jump gears; if it's too loose, it'll do all kinds of weird stuff (really, it's bad; maybe I should've taken some video of mine).

What worked for me was making sure that the cable would start pulling immediately when the shift lever was moved -- but to not be so trigger-happy that it pulled too much.

I had accidentally taken virtually all the tension out of the cables, so doing the quarter-turn-at-a-time with the barrel didn't have any effect. Both the front & rear shift cables ran along the downtube, so they were easy to examine. If I flicked the cable with my fingers, it would just flop lazily. The derailleur finally started behaving when I took out all the slack -- but if I made it too taut, it would start misbehaving again.

So, it ended up working best just a few turns on the tight side from being slack. Once the cable had enough tension, it would make a distinct musical pitch as I plucked it. I didn't keep track of the actual concert pitch it produced, but I began using the pitch as confirmation that I was actually adjusting cable tension. It worked much better than trying to eyeball the derailleur's motion & alignment, and I was still clueless when it came to watching how the chain shifted across the cogs.

Of course, this relies on the shifter's index function, too. If it's good, it'll work exactly as designed. It just won't work if it's damaged somehow, though.