Shifting problems can sometimes be difficult to diagnose.
This video will address some common sources of poor front derailleur performance, and how to fix them.
Calvin Jones here, Park Tool Company.
The most common fixes for shifting problems are the basics:
proper alignment,
setting of limit screws,
and adjusting the index setting.
For a walkthrough of these procedures, watch this video.
However, if you've already checked these settings and things still don't seem quite right,
here are some other issues to look out for.
A common source of shifting problems for both front and rear derailleurs can be found in your cable system.
The cable system is the housing and the inner cable together.
Dirt and grit can work their way inside.
This creates friction along the system, which will slow the shifting both directions.
On most bikes you can get a closer look at the cable by putting the bike in the lowest gear.
Then without pedaling, shift the derailleur to slacken the cable.
Remove the housing from the stops.
Feel the cable and feel how the housing slides.
You can also wipe the cable and throw on some lube.
Put the housing back and see if it helps.
But if the bike has full housing without stops, that doesn't work.
You will need to loosen the pinch bolt to get a feel for how the cable is operating.
If it feels gummy, install new cable and housing.
Also inspect outside of the housing, especially at the ends.
Damage anywhere along the system isn't helping our shifting.
Replacement of the housing and the cable is the best option.
The next issue is a bent cage.
this cage can become bent on impact from a crash
Re-bending a cage is difficult.
You often end up with multiple bends because it is difficult to isolate the first bend when attempting a fix.
Replacement is really the best option.
The chainrings will eventually wear and the chain will not engage well on a worn ring.
A chainring tooth can also become bent as a result of impact.
A bent tooth will make a noise and sometimes catch the chain.
While replacement is an option, it's often possible to re-bend the tooth.
If a bent tooth breaks on rebending, you might try the chainring anyway.
Even without that single tooth, the ring is likely to work fine.
Another issue is that a chainring can exhibit extreme wobble as it spins.
This can make for inconsistent shifts and make setting limit screws and index adjustments difficult.
First double check that all mounting bolts are appropriately tight,
noting that chainring bolts require significantly less torque than a crank bolt.
If the chainring is bent, replacement is the best option,
That's it for advanced front derailleur troubleshooting.
If you're still having problems shifting,
you can find more potential causes in our troubleshooting text article at Parktool.com,
or bring your bike to an experienced mechanic.
Finally, be sure to check out the Park Tool guide to derailleurs
for an overview of all of our derailleur and shifting content.
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