Yes, I know about plucking wheel spokes to check tension by musical pitch:
http://www.bikeforums.net/showthread.php?t=356361
And this is
partially related to this thread:
http://www.bikeforums.net/showthread.php?t=356361
I was feeling that my Shimano-equipped road bike's shifting wasn't quite right, so I ignorantly started fiddling with the inline barrel adjusters.
Okay... "fiddling" is too kind of a term. I was spinning those suckers who-knows-how-much to see if I could get the derailleurs to move.
So, rather than taking the bike to the shop and pleading, "I broke my bike, can you make it work again?", I decided to finally figure it out myself. In lieu of a workstand, I hung it by the saddle off of my doorway pullup bar and start spinning the cranks & shifting the levers.
The derailleurs seemed to be aligned, and their travel stops seemed correct. That was easy.
However, I just couldn't get the danged chain to shift reliably from one cog to another. No matter which way I turned the RD barrel adjuster, the chain invented new ways of misshifting.
For some reason, I started looking at the cable, particularly the section that runs along the downtube.
While on the small cog, it was
slack. I could tug it at least a whole inch. I figured that, even on the smallest cog, the cable should have at least some tension so that the RD would start shifting right away when the lever is moved.
I think it was partly because of where the bike was hanging -- the door frame & pullup bar probably resonate well enough -- but after
finally dialing most of the slack out of the cable with the barrel adjuster (I really, really spun it before!), I could hear the cable make a pitch, about the range of an upper bass guitar string.
*Pluck pluck pluck* I went, raising the cable's pitch by a step or two.
BINGO -- the shifter actually began working correctly!
It wasn't yet perfect, but man, it was better than before. Rather than just trying to count turns in the barrel adjuster, I started turning it while plucking the cable, making sure that I actually turned it just enough to change the pitch a bit, thereby changing the tension while shifted onto the smallest cog. It was like I was
tuning the cable. Change the pitch another quarter-step or less, flick up & down through the gears, change the pitch again, test again.
Awesome. I un-broke my RD.
The FD's barrel adjuster had also been subjected to my ineptitude, so I started on the other side. I didn't even try test-shifting at first -- I just set it to the small chainring, then started turning the barrel adjuster while plucking its cable along the downtube.
After turning the barrel for a while, I started getting tension again, and the cable started making an audible pitch. Same thing as for the RD -- pluck, check the pitch, shift a few times, turn the barrel, pluck, etc.
Awesome. I un-broke my FD.
Just to be sure, I took it for a few laps around the block. Each click of the right lever once again changed one cog; three clicks, three cogs -- seven clicks, seven cogs. The front shifter was working well again, too. I could even use the mini-click to trim it and avoid rubbing the chain while in the small-small combination.
At last! Success! I can go to bed now... well, after I get the laundry from the dryer...
