My chain rubs against the front derailleur when I am on my large chainring and smallest cog. But it is not a consistent rub, it only rubs once with each pedal revolution. As if the chainring were bent.
If I set the derailleur with more room, then the chain derails to the outside of the chainring.
The chainring doesn't seem bent (though a few teeth have seen better days) and the problem is definitely worse when pedaling hard or sprinting.
If the chain goes off the chainring, at very least the set-screw on the FD is out of adjustment. And quite possibly the position of the FD is also not right. So before we blame the chainrings, or something else very expensive to replace - here is the standard cure for an ailing FD (front-derailleur):
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.
Adding a barrel-adjuster can solve many problems with the cable coming loose - or being too tight.
Originally Posted by Cateye
Only panthers007 is stupid enough to believe that this is a good idea.