New to all of this, so I don't really know the terms. Bear with me.

Got a bike from a garage sale about a year ago, in nearly brand new shape, haven't really rode it.

Over the past few months I've been using it quite often, biking roughly 8km to and from work.

Yesterday, the chain was skipping, and then later fell off of the largest front gear, to the right. Since then, if I put a heavy load on the pedals, such as biking uphill, or attempting to accelerate really quickly, it will fall off.

I've looked into fixing the front derailleur, and played around with the two unlabeled screws out front, but had no luck.

The chain still falls off due to heavy load, regardless of the position of the screws adjusting the front derailleur.

Unfortunately, I an not too sure if my front derailleur is properly "calibrated", and was debating on playing with it until the chain maybe fell off less? I seem to have gone through a bunch of options with no luck.

I'm assuming that the front derailleur isn't he problem, or that I should keep adjusting it until the problem stops.

In conclusion, I am not too sure what to do. Do I seek a new problem, or do I continue adjusting the front derailleur?

  • Trying moving the front derailleur as far to the right (towards the largest front gear). Also move the chain to the smallest gear on the back. Now look at the bike from behind and see how this derailleur lines up with the gear. It should be right enough that the chain is not touching the derailleur but left enough that it is not 'off' the chain ring. You can adjust the limit screws to limit how far this derailleur can move to the right. Keep turning the 'H' limit screw little by little (1/4 turn) and get the derailleur as close to the chain as possible without it touching. – Abubakr Jul 13 '16 at 15:05
  • I tried to do this yesterday, and the chain still seems to fall off to the right. Should I get the derailleur to touch the chain, then gradually move it away so that there is a slight space between them? Also, how can I defferentiate between the screws? I've got two and both of them seem to do nothing. – Eddie Jul 13 '16 at 15:11
  • Could you have knocked the front derailleur such that it has moved? It certainly sounds FD-related. – PeteH Jul 13 '16 at 15:28
  • I don't think so, I don't recall hitting it or displacing it in any way, and I only ride it in the road, so I don't think it could've been bumped.or dislodged either. Is there any way to move or shift it back to its original position, if I had had moved it? – Eddie Jul 13 '16 at 15:32
  • 1
    That's probably wrong; read www.parktool.com/blog/repair-help/front-derailleur-adjustment – Batman Jul 13 '16 at 15:50

First verify these assumptions: The chain rings are not bent (causing unintentional shifting), the chain ring teeth are not badly worn or the chain itself is not worn and stretched (causing the chain to jump teeth and perhaps feel like shifting), the bottom bracket is correctly adjusted and not wobbling (causing contact with the cage and unintentional shifting), and the leading edge of the large, inner Front Derailleur (FD) arm is not bent away from the bike (forcing a shift completely off the large chain ring).

How your FD works: As the FD cage moves in and out, one or the other of two arms of the FD cage puts sideways pressure that shifts (de-rails) the traveling chain from chain ring to chain ring. The FD should be securely attached in the correct position on the Seat Tube so that at no point in its travel does either cage arm contact any part of a chain ring and at no gear combination does the chain itself drag on the rear spacer that holds the two FD arms together to form the cage. The arms should be smooth (not worn), parallel with each other, and parallel with the chain rings (and therefore in line with the chain that is traveling through the cage.) The FD spring typically forces the cage towards the IN position. Pulling on the FD shifter cable forces the cage towards the OUT position. The inner cage arm is typically wider and longer than the outer cage arm because it requires more pressure over that larger surface area to lift the chain up to a higher gear than it needs to simply drop the chain down to a lower gear. The two adjusting screws are used to limit how far in each direction (IN or OUT) the cage can move.

Now let’s do a complete FD adjustment with the bike suspended in your work stand: While hand pedaling the chain through the FD cage, carefully shift and center the FD cage over the small inner chain ring. Shift the Rear Derailleur (RD) into the largest freewheel sprocket (closest to the wheel). At this point, there should be only very slight tension (and no looseness) on the FD shifter cable. Loosen the cable clamp at the FD and adjust the inner limit screw until the cage is exactly centered above the small inner chain ring. Remove any slack in the FD cable at the FD cable clamp and tighten in place. Shift the RD into the smallest freewheel sprocket (furthest from the wheel). With the chain moving through the FD cage, shift and center the FD cage over the large outer chain ring, and verify the chain is not touching either cage arm and the cage is clearing the large outer chain ring. Now tighten the outer limit screw. Test all possible shifting combinations several times while hand pedaling on your work stand―first slowly then faster and faster.

  • Welcome to Bicycles @Steve. Nice first post. Cheers – andy256 Sep 7 '16 at 1:35

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