Junkbeast

I've got about 2K miles on this groupset/bike but the downshifts on the rear are sometimes bad. Most of the time if I do a single click down, the chain tries to move onto the next bigger ring, but it only goes about halfway, staying in the present gear but audibly rubbing the teeth on the next biggest ring. I have to push the shifter another half-push (no click) to move the chain. If I push past the click to downshift 2 gears at a time, that works pretty much every time, but sometimes I don't want to go down 2 gears. Upshifts from large to smaller ring are crisp and precise each click.

I've never really had to adjust my derailleur before and am trying to learn to do it myself but I don't want to go too far with it and make it worse. I found this page https://www.sheldonbrown.com/deraile...ment.html#rear and it seems I need to loosen the low gear limit stop a little. I want to try this. Does this sound right before I start messing with it?

alcjphil

Don't touch the limit stop, the barrel adjuster is used for adjusting gear selection. If you loosen the low limit screw you could send your derailleur into the spokes

oldbobcat

Use the cable adjuster on the derailleur or inline on the cable to pull a little tension on the cable. One or two clicks at a time. And don't mess with the limit screws.

Andrew R Stewart 

After a couple thou miles one should expect some cable friction issues, especially if internal routing is in play or if any real wet riding has been done. Also check the inner cable condition inside the shift pods where the cable is out of sight. A fraying cable will have some of this same lack of index tracking. Andy

Iride01 

Limit screws won't help at all for shifts unless it's on the biggest or smallest sprocket that you can't quite get into. And only then after checking that the DR is in fact solidly against the limit.

If your issue was when shifting to a smaller cog and you had STI's, then I'd say to remove the cable from the shifter and see if it's frayed near the end.

Going from smaller to larger cogs is likely just cable adjustment which might be corrected with the barrel adjuster or inline adjuster. Possibly your cable is slipping in the hold fast making any other adjustments just temporary fixes.

Retro Grouch 

Since it's downshifting when you have the problem I doubt it's a cable friction issue. Cable friction is more likely on upshifts.

You are most likely experiencing a slight amount of cable stretching. That's common in relatively new bicycles. If that's the case, a quarter to a half turn, counter clockwise on the barrel adjuster adjacent to the rear derailleur should fix it.

sean.hwy

As other have said, do not touch the limit screws.

I used the park tool video to help adjust my rear derailleur.

dsbrantjr

And getting the broken-off end out of the shifter is exquisite torture, so best to catch if beforehand.

Junkbeast

Thanks all. Glad I didn't mess with those screws. I'll look at stuff people mentioned and mess with that barrel adjuster tomorrow.

dsbrantjr

You should only need to adjust the limit screws if something changes, like a new cassette or derailleur or if the derailleur hanger is adjusted.