Front Derailler indexing

CJSA330 Posts: 9
edited September 2010 in Workshop
I have Tiagra throughout, whilst riding the other day the front derailler got itself stuck on the large chain ring. The small shift lever wouldn't move the cable or click.

As the bike is 2nd hand, I've had a go at adjusting the front derailler my self, by slacking the cable at the pinch bolt. Basically I've got it all moving again, but the indexing seems wrong on the shifter.
It now take 2 clicks to move to from the large to the small chain ring. The first click doesn't seem to move the cable, then moving the shifter again moves it to the large ring ok.

Is there anything simple to adjust before I head for my lbs ?


  • jgsi
    jgsi Posts: 5,062
    I have just copied and pasted this from a pdf I use as a crib sheet whenever front derailleur needs adjust after any messing about (thankfully pretty rare) Hope it helps and saves a visit to the shop.

    Front Derailleur - Adjusting L-screw
    The L-screw controls the inward most travel of the front derailleur. Set adequately, it allows
    the chain to shift to the smallest ring, but not beyond so it falls off.
    1. Shift chain to innermost rear sprocket and innermost front chainring. Inspect derailleur
    for marking indicating "L" screw.
    2. Check inner wire tension. It should be fairly loose at this time. If inner wire is taut, turn
    barrel adjuster clockwise into housing. The barrel adjuster is typically located where the
    cable housing enters the shift lever. If barrel adjuster is already fully turned into
    housing, loosen inner wire pinch bolt, slacken inner wire and retighten bolt.
    3. Sight gap between inner chain plate and inner cage plate. Only a small gap should be
    visible, about 1/16" or 1mm

    Pedal bike slowly and continue to sight gap. Set clearance at tightest point in chainring
    rotation. Adjust L-screw so there is a small gap between inner cage and inner chain
    plate. Pedal bike and check that chain is not rubbing cage as chainrings turn.
    1. If there is no gap and chain is rubbing cage, loosen L-limit screw 1/8 turn (counterclockwise).
    Inspect for gap again and repeat until slight gap appears.2. If the gap
    appears larger than 1mm at its widest point, tighten the L-screw, in small increments,
    until the gap closes.
    5. Test the shift by shifting chain to next chainring then shift back to the innermost ring.
    Do not use the shift lever. Pull on the inner wire to shift the derailleur. Using the lever
    may confuse limit screw issues with cable tension issues. If chain shifts quickly, limit
    screw setting is adequate.
    6. If the shifting appears is slow (requires more than one pedal revolution to initiate shift),
    turn L-limit counter-clockwise 1/8 turn and repeat test. Repeat 1/8-turn increments
    until shifting is adequate. The gap will open wider than the 1mm target, but will still be
    as small as possible with adequate shifting.
    7. If chain is shifting beyond the inner ring and falls off the chainring, gap may be too
    large or cage alignment may be off. Tighten L-screw 1/8 turn and check shift again. If
    chain ends up rubbing inner cage of derailleur, yet still drops off inner ring when
    shifting, other problems such as chain line or derailleur rotation exist.

    Front Derailleur- Adjusting H-screw
    The outward travel of the front derailleur is stopped by the H-screw. When viewing the H-limit
    adjustment, make sure there is enough tension on the inner wire by either keeping extra
    pressure on the lever, or by pulling the exposed inner wire taut by hand. Use a rag to protect
    your hand if pulling the inner wire. After the H-screw is adjusted the inner wire should be retensioned
    to assure proper shifting.
    1. Shift to outermost sprocket in rear and outermost front chainring. Inspect derailleur for
    mark indicating H-screw.
    2. Pull inner wire with hand to increase tension to insure derailleur is against H-screw.
    3. Maintain full pressure on inner wire and check gap between chain and outer cage plate.
    Only a small gap should be visible, about 1/16" or 1mm. Pedal bike slowly and continue
    to sight gap. Set clearance at tightest point in chainring rotation.

    A. If chain is rubbing cage, loosen H-screw 1/8 turn and pull fully on inner wire. Check
    gap again.
    B. If chain is not rubbing, tighten H-screw repeatedly until chain is 1mm
    4. Test shift to the large ring. Shift derailleur from next to largest to largest ring using
    hand pressure on inner wire rather than shift lever. If shifting is slow, loosen H-limit
    screw slightly and repeat test. If chain shifts off the outside of the large chainring, the
    outer-limit is set too loose. Tighten H-screw limit and test shift again.

    Front Derailleur- Adjusting Indexing (Two Chainring Bikes)
    Some front derailleur systems have an index setting. If the shift lever has two distinctive stops
    or clicks, it is indexing. If the front shift lever is friction, there is no index setting.
    1. Shift chain to outer chain ring in the front and outermost rear cog.
    2. View gap between outer cage plate and chain.
    3. If outer cage plate clears chain, index setting is adequate.
    4. If plate is rubbing chain, increase inner wire tension by turning adjusting barrel
    counter-clockwise and check again.
    5. If barrel adjuster is all the way in or out and no adjustment is possible, reset inner wire
    tension. Shift to innermost chainring and loosen inner wire pinch bolt. Pull the wire with
    fourth-hand tool and tighten pinch bolt. Begin adjustment of inner wire tension as
    6. Test shift of front derailleur to both front chainrings.
  • ... re=related

    This guy tells you in a verrrrry easy way.
    The dissenter is every human being at those moments of his life when he resigns
    momentarily from the herd and thinks for himself.
  • Fairly simple, adjust screws so they just derail and not plop off either side. Don't know why you'd need to pull the inner :roll: just unscrew the allen bolt, move derailler by hand whilst pedalling. if it plops off movement is too great. If it doesn't go to smallest or largerst, movement isn't enough.
    Say... That's a nice bike..
    Trax T700 with Lew Racing Pro VT-1 ;-)