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Rear Derailer wont shift the same between sm and Lg chainrin(6 posts)

Rear Derailer wont shift the same between sm and Lg chainrinsurf
Feb 26, 2002 10:30 AM
Cant seem to get the derailer adjustment perfect. While in the small chainring (39) the rear derailer works better with more tension and is perfectly alligned as far as the pullys and cogs ect. But when I shift to the large chainring (54) the derailer wont shift down to smaller gears, I have to turn the barell adjuster clockwise a turn or so.

While on the small chainring there is a bit of chain rub even though the angle adjustment is screwed all the way in. One guess is that the chain may be to long, could taking a link or two out increase the tension? Or could I re-adjust the rear-derailer spring to increase tension. The derailer is ---hold your breath-an older DA 7-speed (along with 7-speed freewheel). I know, some will say just get new gear but for the moment (I'm pretty new to the bike thing) ill stick with what I have. And besides I have learned a lot fixing everything on this bike. Thanks for all the help
Check Thisgrzy
Feb 26, 2002 11:38 AM
Verify that the rear der hanger is in fact parallel to the rear wheel using something like the Park Deraileur Adjustment Gauge (DAG-1). If this isn't right the bike will never shift right and you'll drive yourself nuts. Given that you're running 7 speed one can assume that the bike is older and that at some point in it's life the hanger became tweaked. A very common problem actually. Getting chain length right is important, but wouldn't be the cause of this problem.
the hanger is OKsurf
Feb 26, 2002 11:54 AM
I broke a chain and while fixing it the(i did not have my tool with me) LBS also slightly bent the hanger for me and the bike shifted great afterwards. But it's not perfect so thats why i posed the question. I can get the bike to work great in the small or large chainring, but not in both???
Thanks for the thought though
re: Rear Derailer wont shift the same between sm and Lg chainrinChen2
Feb 26, 2002 1:54 PM
How old are the cable and cable housing? If the cable has a lot of drag in it the derailleur will be slow and hesitant to shift into the smaller cogs.
(54t ring? Holy Moly!)
re: Rear Derailer wont shift the same between sm and Lg chainrinnumber8
Feb 28, 2002 2:43 PM
7 Speed der. means it is old. Therefore the spring is starting to weaken. When in the large cogs there is enough tension to pull the chain down the gears, but when you get down to the lower gears the spring does not have enough tension to pull the chain down a gear. The angle of the chain coming off the chainrings would account for a difference in the shifting between the large and small ring. Just a thought.
re: Rear Derailer wont shift the same between sm and Lg chainrinmackgoo
Feb 26, 2002 3:30 PM
How is your rear hub. I had a sloppy shifting problem, it turned out to be a sloppy rear hub.