I just took delivery of a new Cannondale Quick CX3 bicycle. The drivetrain was already set up, so all I had to do was install the front wheel, seat, and handlebars.
The first time I took it out for a ride, I noticed a scraping sound when pedaling in the highest few gears (large front chainring). After putting the bike on a stand and rotating the crank, I found that the chain scrapes against the outer part of the derailleur cage at some points around the rotation of the chainring. Is there a simple adjustment I can make to move the cage a little bit outward (away from the bike) ?
@cappellof This will depend on the rear cogs as well. If you're in large in both front and back (or small to small), this puts the chain at an extreme angle, known as cross-chaining. You generally just want to avoid those gear combinations. Even a perfectly adjusted bike might still rub when cross-chained. That would more likely rub on the inside of the cage, though.
Since your's is rubbing the outside of the cage, you probably either don't have enough tension on the cable so that it's unable to pull the cage far enough, or the high limit screw is preventing it from moving further. To check, push on the lever to try shifting up even though there is no further gear: does the cage move a little bit further? If not, the limit screw is too tight. It should be labeled with an H on the derailleur body, loosen it a quarter turn at a time until the rub stops. If the cage DID move, then it's probably the tension. Rotate the barrel adjuster by the shifter counterclockwise to tighten the cable, again quarter turn at a time.
Lastly, it's possible the angle of the entire derailleur cage could be slightly off, but I'd say that's unlikely.
Park Tool has a great video on this (and lots of other adjustments too) https://youtu.be/ZNG7g83lI-s
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@cappellof thanks for reaching out about the issue you're having with your front derailleur. We will tag a few of our bike techs for their advice on best next steps @REI-JessieD @REI-ReinkeM @REI-JacintaH @REI-CassidyT @REI-MeganR.
Also, even though you posted on the 'Ask an REI Employee' board, you may receive responses with advice from community members who are not employees. You can always identify an REI employee by their username (REI-name) and title (REI Employee, REI Moderator, REI Community Manager).