Hi I know that this issue is brought up a lot and I could not find an answer to my questions in my search. I am trying to adjust my RD (Shimano 105) to dial in my shifting and when I have it on my stand I can get it to shift pretty well but when I take it around the block to test it out I have a few issues. My larger cogs seem to shift pretty smooth but when I get towards the larger cogs the shifting becomes very clunky. It seems like when I click to shift that it shifts really loud and rough. Also I have one cog somewhere in the middle (cant remember exactly which one because it was a few hours ago when I was testing it and forgot to note exactly which one) that it wont shift into until I click one more gear. I am fairly new to cycling and learned to adjust my RD on my own so I am looking for any advice. (also from what I can tell my RD hanger appears to be straight and not bent) My questions are:
1. Why do some gears shift smoothly while others are rough/clunky and how do you fix it?
2. Why would only one gear not shift correctly but the rest do and how would you fix that as well without messing up the rest of the shifting?

Hopefully I gave you enough information and if you have any other questions just let me know and I will try to answer them as soon as possible. Thanks

Derailer Adjustment

click on link above

Yup. Derailer adjustment should fix the issue. You should be able to adjust it just with a cable tension barrel adjuster. If that didn't help to completely get rid of the shifting issue to the largest cog, you may try adjusting L screw little bit.
Its a pretty easy process. Also make sure your wheel is mounted correctly. Just lock your qr when the bike is on the floor.

Another thing that could make for inconsistent shifting would be a bent derailleur hanger. Basically, the derailleur should run parallel to the cassette. If it's bent, it won't index correctly with the limit screws set correctly and with any amount of indexing adjustment.

Yet another thing would be friction in the cable/housing. You can check this by loosening the cable anchor and pulling the cable through different sections of housing, looking for friction.

A bicycle is a simple machine but the devil is in the details. If you think about it logically, the shifter pulls a measured amount of cable and that cable pulls the derailleur a set amount. Assuming you have matching parts: the cable tension can be wrong, the shift cable is binding up, or the derailleur and cassette are somehow not aligning.

If it ever worked right you can assume the parts match. Limit screws don't move on their own so you can exclude them. Most guys by the time they get to your point can identify sticky cables and will fiddle with cable tension till they get frustrated. That leaves derailleur hanger alignment. If you have a 9-speed or 10-speed cassette it doesn't have to be very far off to screw up your shifting.

Need more info (and for others the info below is helpful for most issues)

• When did the problem start - sudden or gradual onset?
• Was there an incident or repair procedure just prior to the onset?
• How old is the bike or components
• What exact procedures have you tried and what source are you using for guidance? "Fiddling" does not count as a procedure!
• For drive train problems what is the front/rear combo in which the problem does or does not occur? (use small/middle/large in front and tooth count, in the rear 3rd smallest, largest, etc. and tooth count - not 1st gear, low gear, etc.

+1 - When I have experienced poor rear shifting under load, it has usually been a cassette and/or chain that needs replacing.

Thanks everyone for the input. To answer some of the questions it started after I took the bike up for a full servicing at a LBS to get ready for the summer. I contacted the shop and they said I could bring it in and they would do whatever to fix it. (I have not taken it back yet because it is just over an hour drive and we don't make it there too often and I had adjusted my RD before so I thought I could just adjust it myself before driving all the way back up there.) I am going up there at the end of the month and if I can not get it sorted out by then, I will be taking it back to them. The bike is fairly new (2012 with about 1000 or so miles on it) and when I got it serviced, the tech checked the cables and said that they did not need changed. I have tried the barrel adjusting several different times to get it exact, I did not mess with the H and L screws because the limits didn't seem to be a problem, and I did try to adjust the B screw so that it would be closer to the largest cog but it is already as loose as it goes. Any looser and it would just fall out. I took the bike out for a 25 mile ride today and it seemed to be able to shift to each gear with each press of the shifter but from ~ middle cog down to towards the smaller cog the shifting was still clunky. I just want it to be consistently smooth through all of my gear shifts. Are there some things that kind of just work themselves back into order over time like that? Hope that helps a bit