Lenaxia

hey guys, I'm in a bit of a predicament.

We tore down and rebuilt my girlfriend's bike and I'm having trouble getting the RD to index properly.

She's running a 6510 Ultegra Brifters and a 7700 DA RD.

It should be noted, her RD shifted kinda strange before we tore it down but I had gotten it to a point where it was shifting more or less smoothly (she said it felt better than the 6700 grouppe she tried out).

What I'm faced with now is that I cannot get smooth shifting across the entire range of cogs. If I adjust the barrel so the biggest cogs shift smoothly, one of the lower cogs skips; if I adjust the smallest cogs to shift smoothly, all of the big cogs skip.

I confirmed the limit screws are adjusted properly.

It almost seems that the cogs aren't spaced evenly or that the brifters are not indexing evenly between all gears. Is there a way for me to check either of these? I can't get my calipers onto the cogs to measure due to lack of space.

Any other suggestions on what I can do?

velo-orange

It could be the rear derailleur hanger is out of alignment.

Check to see that the rear derailleur mounting bolt is threaded completely into the hanger, and that it's not cross threaded or wonky.
I'll assume you know what the stroke adjust screws do, and how to fix the cable to the derailleur.
Sometimes you can get more accurate shifting if you trim the barrel adjuster when the chain is on a middle position cog- like 4/5/6 position- so the cumulative distance between 'adjustment point zero' isn;t as great at the ends of the derailleur movement range.
I hope that makes sense.

But yeah, it may be the deraulleur hanger is bent or the der cage is tweaked. There might be a missing spacer, but it would be pretty obvious- the cassette would not even be close to tight.

Camilo

This may or may not help you, but this is how I tune my rear indexing. It really only takes a minute or two.

Shift into one of the middle cogs. Doesn't matter which one. Doesn't matter if it's a little noisy at this time.

While pedaling the bike, turn the cable adjuster counterclockwise (tightening the cable) slowly to cause the derailleur to shift on it's own to one cog larger. In other words, you're not doing anything with the shifter, just tightening the cable. Stop adjusting as soon as it shifts.

Then, moving the barrel adjuster 1/4 turn at a time the other way - clockwise - turn the adjuster in small steps until it shifts down to the "correct" cog, and then keep turning it clockwise until it just shifts onto the next smaller cog. Again, stop right when it shifts. Count the 1/4 turns while you are doing this. From the "larger" to the "smaller" cogs it will probably come to something like 15-18 1/4 turns, but that number doesn't really matter as long as you count. It's easy to count, because that barrel adjuster at the rear derailleur usually has detents every 1/4 turn.

Then, turn the adjuster back the other way - counter clockwise - counting your 1/4 turns and stop at 1/2 the number you counted earlier. This will cause the derailleur to move back to the "correct" cog, but it will be exactly in the middle of the correct cog, not a little one side or the other. This should give you perfect shifting.

If that isn't your problem, then you need to start at step one and follow the shimano and/or park tool directions for derailleur installation, cable routing and initial adjustment very carefully step by step, even if you have done an RD install before. Then fine tune it with the above.

Pay close attention to your cable condition and especially routing.

Old Hammer Boy

All good suggestions. First, make sure your cable is totally slack when the chain is on the largest cog, and fully tight on the smallest cog, then adjust for clean shifts as described above. If you still have problems, it's most likely a cable problem.

rm -rf

I had the same problem with my Campagnolo derailleur a few years ago. Either the big cogs were perfect, or the small cogs, but not both at the same time. It turned out I had the cable clamped wrong. On the clamping bolt, there's a washer with a bent ear to locate the cable correctly, but I had it on the wrong side of the ear. That altered the angle of the cable enough to mess up the shifting. It drove me crazy, I checked a bunch of other things before seeing the correct cable routing at the LBS.

Is this your derailleur model (Shimano Service PDF)? See the two cable clamping locations.

Other than that, have the LBS check the hanger alignment. I don't have the tool, but I did a quick check on mine with a long straight edge laid flat on the hanger, with the derailleur detached. The distance to the wheel brake track above and below the hanger matched exactly. ( And I was certain I had not banged the derailleur or dropped the bike.)

The Park Tool derailleur adjustment page is very good. It starts from the beginning, and goes step-by-step. Maybe that'll help to start the adjustment from scratch.

bkaapcke

Check to see if the cable is attached on the correct side of the pinch bolt. bk

Lenaxia

Hey guys, thanks for the tips, the cable was indeed on the wrong side of the pin. It shifts beautifully again now!