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My bicycle's gears are 3x7 when i keep it on 2x1,2x2,2x3,2x4,3x1,3x2 or 3x3 my bicycle's chain rubs with my front derailleur on the left side. Is it normal ? if not then how can i fix that?

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2 Answers 2

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No, it's not normal.

The front derailleur is adjusted by three mechanisms:

  • Indexing. This sets position of derailleur on two biggest chainrings. Position on smallest chainring is set by low limit stop (although indexing may affect it too if low limit stop is incorrectly adjusted).
  • Low limit stop. This prevents rubbing on smallest front chainring
  • High limit stop. This prevents you accidentally pulling the front derailleur so much to right that the chain falls on the crank. However, indexing should prevent it too, but in case indexing is off, high limit stop offers additional safety.

Sounds like your indexing is off, and the cable is too tight. Find the barrel adjuster, it's either in the front gear lever, in the front derailleur or somewhere on the cable. If it's in the front derailleur, it may be hard to find it and you may find it useful to search for manuals of your front derailleur type.

You need to loosen the cable tension. So if the indexing is in the cable or in the lever, tighten the barrel adjuster. This makes the housing shorter, which effectively is the same as making the cable longer (less tension).

If the indexing is in the front derailleur, you need to find the direction you turn the screw: test both directions and see which direction helps.

Note that two very similar screws side by side at the front derailleur are the low and high limit stops. Don't adjust them at all in this stage.

Also make sure that your front derailleur is straight. If it's at the seat tube using a clamp, it's possible an impact has made it turn sideways. If this is the case, you see it by noting the cage is not parallel with chainrings. In this case, you loosen the clamp, rotate the front derailleur at optimal alignment and tighten the clamp again.

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The tension on the front deraileur(FD) sounds too tight.

Put the bike in 2x1 (middle ring front, largest back). If the cage touches the chain on the inside/left side there is too much tension on the FD.

Screw the barrel-adjuster at the gear handle clockwise to tighten it (this will relieve the tension and move the cage inwards). Start with e.g half a turn. Do some up/down shifts in front deraileur to make the new adjustment settle. Go back to 2x1 and evaluate if the chain is rubbing on the cage on the inside. If yes, you need to repeat the procedure. If the chain is just barely not touching in 2x1 you are finished given no other issues are causing your problem. If you went way too far, loosen the barrel adjustment screw to move the cage outwards again.

If it is rubbing even with the barrel adjuster fully inserted, you need to loosen the cable at the pinch bolt and do the above adjustment with a new slightly elongated cable length.

Note, a slight rub in 3x1 is not necessarily a maladjustment, this kind of cross chaining is not always tolerated even with perfect adjustment.

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