Adjusting front derailleur - complete novice question.

mattstone2000

Ok, so having commuted on an old mountain bike donated by a friend for six months, I decided to get a little more serious and invested in a road bike (a B'Twin Sport 2 16S, for anyone interested).

I'm very happy with my purchase, but I'm having a little trouble with the front derailleur. After about a week of riding I noticed that when the chain is at its outermost position (i.e. when positioned on the small cog on the rear gears) it would rub against the outer edge of the chain guide.

I tried tweaking the two 'adjustment screws' on the derailleur, but a mixture of naive exuberance and confusion over which screw did what has made the situation worse! Now the chain rubs against the inner edge of the chain guide when in its innermost position as well as the old problem of rubbing against the outer edge when in the outermost position.

I can't seem to make the chain guide go any further in either position, so that the chain doesn't rub. Are there any other adjustments I can make? Is this normal? Help!

Smokin Joe

The cable has suffered from a bit of initial stretch and is too slack to shift the mech far enough across. Put the chain on the small ring, unclamp the cable and pull it tight so all the slack is gone. Then re-adjust the stop screws so there is no rubbing and it does not overshift and throw the chain off.

mattstone2000

Ah, thanks for that.

When I reclamp the cable, what position should the stop screws be in? Should I unscrew them as far as I can?

lateralus

No. The screws are there to set the limits of deraiileur movement (to stop the chain being thrown off the inside of the small ring or the outside of the big ring).

Instructions on how to set the limit screws (and other aspects of adjustment) are here:

http://www.parktool.com/repair/readhowto.asp?id=75

mattstone2000

Thanks for the link.

I get it that once I've clamped the cable I need to adjust the screws to set the derailleiur movement. But do I need to set the screws to a particular position beforehand, when I unclamp, tighten, and then reclaimp?

lateralus

I don't think it will make a difference while you tighten the cable. Those screws don't affect cable tension, only the limits of movement of the derailleur. Just follow the Park Tools steps to reset the lonce you've tightened the cable and you should be ok.

Once you've got the limit screws set correctly, you don't need to touch them when you make your indexing adjustments. Over time, cables will stretch and you may need to readjust tension, but you shouldn't need to touch the limit screws unless you'ev moved the derailleur.

mattstone2000

Great, thanks!

geoff_ss

You may find it easier to adjust the screws if you take the load off them by moving the mech away temporarily and then rechecking to see if you've adjusted the right amount.

Geoff