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Sunday, December 24, 2006
HOW TO ADJUST A FRONT DERAILLEUR
A recent comment and request from one of my readers made me realise that I never posted on how to adjust a front derailleur. This is because none of my rides presently have one of these and I just simply forgot about it. So here we go, excuse the crappy pictures, but with the weather I'm stuck indoors and I haven't figured out how to take good ones inside....yet.
The front derailleur is a simple thingamabob that is springloaded and pulled by a cable to push the chain on the gear you want at the pedals. This how-to applies for 2 and 3 gear chain rings. Once you've adjusted with my method, the middle one should take care of itself on a 3 gear set up.
Before you begin, there are a few things to verify. First, make sure the derailleur cage is aligned with the chainring gears. Second, make sure the height is correct by pushing the cage with your hand towards you to make sure that it doesn't hit that last gear. If you need to move the derailleur, undo the cable and loosen the frame bolt and make the necessary adjustements. There, I just saved you at least 45 minutes of yelling, screaming and swearing!
Next, don't bother doing any adjustements before removing the cable from the derailleur. Let's start fresh. At the same time, verify that the cable is moving freely. Cables that are housed in a sleeve up to the derailleur sometimes have a nasty habit of jamming. What happens is that the sleeve's opening points upward on the derailleur and invites water in to deposit itself in there and marries it and the cable with a generous amount of rust. Replace cable and sleeve if that is the case.
Ok, derailleur moves freely by pulling it with your hands and the cable moves freely. Now keep the cable disconnected and put the shifter in the lowest gear position. Your chain should rest on the gear closest to the frame on the chainring(that's the name of the gears attached to the pedals)if you turn the pedals.
Next, shift the rear derailleur to the lowest gear in the back. That's the gear closest to the wheel spokes. Now look at the clearance between the inside of the front derailleur cage(closest to the frame) and see if you have a small gap between the chain and the cage. If the chain is rubbing on it or the gap is too wide, take a screwdriver and adjust the "L" screw on top of the derailleur. Turn the screw until you are satisfied with the results. Clockwise should push the cage outward and counterclockwise inward.
Now to verify that your gap is not too big, leave the chain on the lowest gear on the chainring and shift the rear derailleur to the highest gear, that's the one closest to the frame. If your adjustement is good, the chain shouldn't rub on the outside wall of the front derailleur cage.
Lastly, reinstall the cable and with keeping the chain on the highest gear in the back, shift the front derailleur to the biggest chainring while turning the pedals. Did the chain completely come off the chainring? That's because the front derailleur cage went too far and pushed the chain off. You will need to turn the adjustement screw "H" clockwise until the derailleur stops just before pushing the chain off the chainring. The reverse is true if the cage doesn't go far enough and the chain refuses to go on the last chainring.
Til next time, ride safe and Godspeed.