Drivetrain Issues
 

Hello hello,

Here is the setup giving me trouble: Colnago super w/ (I think) sugino BB,campy gran sport crank/chainwheel, suntour freewheel, campy super record rear derailleur, no front der. The chain is not too worn. The LBS took a quick look at it and thought mostly it sounds fine, but there is a squeek in the second to lowest of my five gears. It happens every two or three revolutions, pretty regularly. It's just a quick squeek like "squeek squeek" or "squeek squeek squeek". The guys at the LBS said it looked like the oil was fine. The tech at the LBS used some penetrating grease on it cause he said it was the pivot on the rear der. I doubt it's too serious, but I hate the sound thinking it might become worse. I was going to re-oil my chain but they said I don't need to. Dunno what to do on this. I only switch out of this gear a few times over the 30 mi a day I go, so it's an important gear to me. =/

Also, when I'm in the lowest gear available, which is using the largest rear gear and the largest front gear (I think), it isn't pedaling smoothly. For a very split second maybe twice a revolution, the pedal feels like it lightly jerks into something, and makes a little sound. It's not a squeek, but more of a thump feeling. I think it's possible it's still trying to shift, that maybe the rear der is too sensitive. It doesn't sound like it's trying to catch on the next rear sprocket (there is none), but I don't know what it would sound like if it is trying. I can try and feather it down to the point it's shifting to a different gear, but the clunking doesn't go away.

Totally clueless here, but I'd really like to stop these issues.

Thanks,

Kyle

I don't know if I quite follow. Do you have multiple chain rings up front? You say "no front der." and then say "largest chainring". That would imply that there is a smaller one, as well.

The biggest chain ring and the biggest rear cog is not your lowest gear. That would be the smallest chain ring and biggest rear cog. If you are running the big ring up front and the big cog in the back you are crosschaining. You should avoid combos that put the chain at a steep angle. That may explain where the sound is coming from.

The sound used to not happen though. The der used to be adjusted looser and like 30-90 miles after it got adjusted I noticed it started. I have two front chainrings, but no front der. The bike was built for one, but it it mysteriously missing. That's how I got it. I'll put one on asap, but they're going for a little high on eBay right now. I just meant that the big front one and the big back one was the lowest gear I could get as I have no front der.

By the way, this is vintage w/ friction shifters from approx. 78-80.

Ah. That clears up my confusion. Try to avoid that gear combo. It will always be your roughest gear. One you get the second chain ring going, avoid the small ring/little cog combo as well.

I'm still quite confused though. I know both of these problems are avoidable, because it was fine when I got it. For the next couple weeks at least, I won't have a front der. Anything I can try to fix it? Does the mechanic's diagnosis that it's the rear der pivoting that causes that squeek? Why would it only be one gear?

Check the B screw adjustment. It regulates how close the pully is to the cog.

See here: http://www.parktool.com/repair/readhowto.asp?id=64