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BICYCLE REPAIR

Front Derailleur Adjustment

Click here to learn about adjusting rear derailleurs.

Equipment:
Round up the following:
  • a way to suspend or hold the bike upright (a car rack works; or use a repair stand, if you have one)
  • 4-, 5-, 6-mm allen wrenches
  • small screwdriver
  • pliers
  • 8/9 combination wrench
  • diagonal cutters
  • lube
  • grease
  • cable end cap
  • adjustable wrench
  • plastic mallet
  • you may also need bottom-bracket adjustment tools
  • Gripping each crankarm with one hand, push and pull laterally to check for play in the bottom bracket (photo). If necessary, use the appropriate bottom bracket (BB) tools to remove play. Depending on what type of BB you have, you may need to remove the crankarm first. Any play in the BB bearings makes it impossible to properly adjust the front derailleur. While you’re working on the crankset, check each crankbolt with the 5-mm allen wrench (or a Torx wrench if you have that type of bolts) to make sure they’re tight.

    Push & pull to feel for play

    Gripping each crankarm, push and pull

    Put a drop of lube on the anchor bolt threads

    Replace rusted or frayed cables and corroded housing

    Replace rusted or frayed cables and cracked or corroded housing by removing the cable end cap, loosening the anchor bolt with a wrench, and removing the bad cable from the housing (if applicable).

    Lightly grease the new cable's head and where it runs inside housing or on the bottom bracket guide and run it through the lever, housing (or BB guide), and stops to the anchor bolt (photo). Don’t tighten the cable or anchor bolt yet. Apply a little lube to the derailleur pivot points and wipe off the excess. Check the tightness of the cage bolt (at the lower end of the cage) with a screwdriver.

    Next, lift the chain off the smallest chainring and place it on the bottom bracket of the frame. Turn the crank by hand while looking at the chainrings from above. Using one side of the front derailleur cage as a reference, observe the trueness of each ring. If they wobble, true them by prying gently with the adjustable wrench (set the jaws just wide enough to slip over the ring). Another way to straighten warped or bent chainrings is to tap on the wobble with a plastic mallet. This takes a little practice, but it works nicely when you get the hang of it. Place the chain back on the ring.

    When viewed from above, an imaginary line through the center of the derailleur cage should be parallel to the chainrings. Next, look at the derailleur and large chainring from the side. Pull the cage outward with your hand. It should clear the large ring by about 1/16 inch/ 2 mm (photo). If necessary, loosen the frame clamp (or for braze-on derailleurs, loosen the attaching bolt) with an allen wrench and adjust the derailleur position.

    You want just a hint of clearance

    Look at the derailleur and large chainring from the side

    Fine-tune the movement with the limit screws

    Adjust the low-gear (inside) limit screw

    Shift to the largest freewheel cog and smallest chainring. Adjust the low-gear (inside) limit screw so there is 1/32-inch/ 1 mm clearance between the inside of the inner cage plate and the chain (photo). Clockwise turns limit derailleur travel, and counterclockwise turns increase it.
    Make sure the front shift lever is in its starting position (shift the chain onto the smallest chainring by hand). Also, make sure that any cable housing is seated inside the lever and the cable stop(s) because otherwise when it pops into place, it’ll create slack ruining your cable adjustment. When the cable and housing is seated correctly, pull lightly on the cable with pliers to remove slack and tighten the anchor bolt with a wrench (photo).

    Pull lightly

    Pull lightly on the cable with pliers and tighten

    Not too close to the crankarm

    Adjust the high-gear (outside) limit screw

    Shift to the largest ring/smallest cog combination. Adjust the high-gear (outside) limit screw so there is at least 1/32-inch / 1 mm clearance between the inside of the outer cage plate and the chain. Also, the cage shouldn’t travel outward so far that it strikes the crankarm (photo).

    Test your work by shifting repeatedly. Move the lever forcefully to stretch the cable, then shift to the smallest ring and check cable slack (photo). Remove slack if necessary as described in step 5.

    Go for a neighborhood test ride. If overshifting occurs (the chain falls off), tighten the appropriate limit screw half a turn at a time and test. If shifts are hesitant, looosen the appropriate limit screw half a turn at a time.

    Remove any slack

    Check for cable slack and remove it

    This article is based on one I wrote for the April 1991 issue of Bicycling Magazine.
    The photos are by Mel Lindstrom. I set up the shots and appear in them.
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