benkoostra said:So I bought a Shimano double D/A crankset for a song last year. I had it put on my 105/Ultegra bike, which was formerly a triple, and it has never shifted well at all. It seems as if the front derailleur never lands in the same place twice. There is lots of chain rub and nonsense, so I have to trim the sucker with almost every shift. It's a serious pain in the butt, and 4 different mechanics have been stumped, except to say that I need a new shifter. I find it strange that this would suddenly be the case at exactly the same time as the new crank is installed.
Do I need a double FD?
The cable is new, and it shifted well before with a triple crank.
Any ideas? Do I need a new shifter?
Who did the work?
Presuming an Octalink crankset, did you replace the 118.5mm BB with a 109.5mm BB?
MOST IMPORTANTLY, do you have the CORRECT chain (width) for the particular front derailleur?
Just substituting an Octalink DA crank for an Octalink 105-or-Ultegra triple won't change the chainring position if you didn't change the BB to one with a shorter spindle.
The shifting WILL BE slightly better (because of chainline to the rear cogs) with a 109.5mm spindle, still good with a 112.5 XTR spindle (double OR triple) and certainly good-enough with a 118.5mm spindle. The 118.5mm spindle should probably only have been used with alloy frames which have 135mm rear spacing ... but, it was a safe spec for a triple.
ALSO. Now a moot point, but for a Shimano TRIPLE, the chain ABSOLUTELY MUST (no matter what you may read elsewhere) match the front derailleur. Similarly, if you use a chain that is too wide (e.g., 8-speed) for the derailleur (e.g., 9-speed), then it will rub AND not index properly.
Definitely, turn the bike upside down to ensure that the cable isn't binding anywhere (e.g., through the BB cable guide) that is obvious with a visual inspection.
Presuming your shifters aren't toast AND the cable isn't binding in an obvious way, then consider changing/ditching the derailleur cable housing ... I used "extra" brake cable housing BECAUSE it's what I had, and the only time I had problems not related to shifting when-under-load (!) was when I mis-matched a 9-speed chain (what I had more of) with an 8-speed 105 front derailleur & 8-speed 105 TRIPLE (yes, rare!) shifter ... At first, I couldn't believe the shifting could go from good to [censored] when I replaced an 8-speed Shimano chain with a 9-speed chain ... I put the old 8-speed chain back on, and the shifting was once again "good."
When an 8-speed chain is mismatched with a 9-speed front derailleur, there just may not be enough space for smooth shifting through the entire range -- different brand 8-speed chains are wider than others ... same for 9-speed & 10-speed chains.
If you do feel a new shifter is the resolution, then you may as well get a pair of Campagnolo Veloce-or-better shifters (well under $150 on eBay for a set) ... but, you will still want to match the chain to the front derailleur. You should be able to get an ORPHANED Left/(front) Campagnolo shifter for under $50 ... the vintage doesn't matter.
BTW. While some/many feel that a "double" front derailleur is better, I prefer to use/install a "triple" front derailleur when I have the option available to me BECAUSE I have the future option to install a "triple" crankset without needing to change the front derailleur ...
The same is true for the rear derailleur -- when I have the option, I'll buy-and-use a long-cage rear derailleur ... my preferance is an XTR rear derailleur.
