Bicycle Mechanics - Front derailleur jamming chain moving to largest ring
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I'm a beginner to the inner workings of a bicycle and learned today that my front derailleur cable wasn't taut so it wasn't shifting properly in the front. After tensioning the cable I am able to shift from middle to low and back again, however when I try to shift to the largest ring the derailleur cage jams the chain for a second or two before it gets it onto the largest ring. Does anyone have any suggestions on what could be causing this? It definitely doesn't shift as smoothly like from the smallest to the middle and being that this was the first time ever trying to move to the largest ring I have no idea if this is "normal".
On a side question dealing with the front derailleur cage... if the chain is slightly rubbing against the cage when I'm in the smallest cog in the rear, is there anything I can adjust to fix that?
07-12-09, 12:13 AM
How far is the derailleur cage from the teeth of the largest chainring? It may need to be raised because it sounds like the chain is just having a hard time getting through the small gap in the derailleur cage and chainring. Should be above 3mm above the teeth.
Its also more annoying because you're working with a triple rather than a double.
Which chainring in the front are you on when you are on the smallest rear cog to cause the chain rub? Are you cross chaining? Do you have a trim option on your shifters? If you're cross chaining, then dont. If you have a trim, use it, and if the trim isn't helping, you need to adjust your limits.
07-12-09, 12:28 AM
What follows was written awhile ago by yours truly. The reason being that at least once a day, someone comes in with the "I'm new to.........and my front-derailleur is....." This is the way most mechanics would suggest for any FD problem:
Take the cable off the FD. Now install it from scratch as per Park Tool Repair:
When you have it properly trimmed and are ready for the cable - a new one wouldn't hurt - you want to pull the cable taut - not too tight, taut. Then apply 48 to 60 inch-pounds to the pinch-bolt. Then put it through it's paces.
It's always easier and faster to install a FD from square-one, than it is to make adjustments with it already attached. This tends to fix one thing - while throwing another out of kilter. Start fresh. You'll get it.
Thanks guys for the info and links! Turns out that I adjusted my FD a couple of rides back and never really tested it fully to realize my adjustments threw things off so today I followed the steps along with the steps in the links to install the FD and now it's shifting smoothly between all 3 rings in the front, as well as the ones in the back. Looked daunting at first, but taking my time to understand the info really helped. Thanks again!
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