Shifts poorly at the cassette
 

Hey!

I've bought a used CAAD10, which shifted poorly, so I bought new chain, cassette (needed bigger cog for climbing anyway) and new cable. None of of which has helped. I've used the parktool youtube as a guide, and also the shimano manual, which I found rather difficult to understand 100%.

I'm starting to wonder if its the rear derailleur or shifter itself. There seems to always be a trade off somewhere.
It will shift rather well from smallest to 6th cog, both up and down. However, for the rest of the cogs, it will either shift well up, but extremly bad down, or opposite.

Suggestions?

Assuming you did everything else correctly (including adjusting the cable and limit screws, and using a longer chain for that bigger cog while not exceeding the derailleur's max wrap), I'd place a wager on a bent derailleur hanger.

Have you checked hanger alignment? Friction in the cables/housing? Gunk in the shift levers and/or derailleur?

Yes, its only a 11-28, which Shimano Ultegra 6700 RD should handle. Also longer chain yes.
It does actually look like the hangar might be slightly bent!

Is there any clever way to check spring tension in the rear derailleur? I have cleaned and re-lubed the RD, but I dont know the springs have become weaker.

Just understand that it's very difficult to accurately eyeball a derailleur hanger's alignment along every axis. The mechanics at your local shop have a nifty tool that both measures and straightens the hanger. It only takes a few minutes.

Could be the hanger but I'm betting not. You didn't replace the housing, did you? That's more important than a new cable unless you have a frayed cable in the shifter. All of the friction comes from housing wear not cable wear...there really isn't any.

No! I'll take it to a bikeshop and buy some housing & get the hangar checked!

Thanks!

Maybe also tell the bike shop that you have problems with the shifting and ask them to find out why.

If all you do is buy some housing and tell them to check the hangar, then many will only do that.

My spouse use to go to the doctor and not tell him/her about any aches or pains she complained to me about because she figured the doctor should find it if there was a problem!

Unlikely source of the problem. Springs don't weaken with age. Things get gunked up and friction increases, but weak springs is a very unlikely issue.

Housing and derailleur hanger are the likely culprits. I have the hanger alignment tool and it really only takes a few minutes. I've used it on a few bikes where I've helped people out and they are always amazed at how much better it works. When you consider that 10/11/12 speed setups have such tight tolerances it is no wonder that a bent derailleur hanger messes it all up.

Always a good policy to start at the beginning when investigating/remediating shifting problems.
Disconnect all cables and remove rear der. from hanger.
Check rear der. hanger alignment...once done reinstall der. Make sure to add a bit of grease to the inner threads of the hanger. Make sure to check that the hanger bolts are tight.
While the cable is disconnected hold the end in one hand and shift up and down the scale to get a feel for the cable movement...is it stiff and clunky or nice and smooth. I usually always replace the cable and housing because it is an inexpensive way to assure of smooth shifting.
I always spray or drip lubricant in the shifter mechanism. Some Shimano shifters, especially the thumb/finger shifters dry out and the shifting doesn't work properly.
Make sure all barrel adjusters are nearly all the way in...I usually leave several threads exposed because I prefer to over tighten the cable just a tad and back off the adjuster rather than use it to tighten the adjuster.
Reinstall the cable, check H/L limit screws...carefully shift up the gears so the chain doesn't come off on the easiest gear...check and adjust limit screw as needed...check B limit screw, adjust as needed.
I do all my cable tension adjustments with the chain on the big chain ring for a 2 or 3 by crank...obviously only one chain ring on a 1 by...but just saying.
I also shift the rear derailleur to the second from the bottom gear...the bottom being the gear with the fewest teeth. I adjust the cable tension until the chain just starts rubbing the next gear up the line then back it off until it is quiet. I run the der. up and down the gears watching for how fast, cleanly and smoothly it shifts. Often, especially as the parts age and wear, you may have to find the happy medium to fast, clean and smooth shifting. I prefer fast, clean and smooth down shifting, from the largest to the smallest gear, it is easier to overshift just a tad when shifting up but it is annoying when shifting down for the der. to hang for a few seconds until it drops down to the next gear.
I always clean the chain, new or old, as well as spraying the derailleurs to clean and lube...lots of gunk can make a bit of a sticky shifting der. then lube and wipe off excess lube after allowing it to soak it in for usually 10 minutes...just a number I've always used.

I picked the bike up from the shop today. The hangar alignment was good, but the shifter was dirty, and the outer casing wasent that good either. He also noted that the end cap on the casing, that sat in the adjustment barrel, was slightly bent, and it was plastic. It should be a metal cap, not plastic, for exactly that reason!

Thanks guys!

And how does it shift now?