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I've just gotten a new bike and run into a problem. When shifting from a smaller cog to a bigger one in the front gears, the chain consistently drops.

The problem happens regardless of whether I'm on a hill or on flat ground, and regardless of how bumpy the road is.

The bike is a Cannondale Quick 6, and I believe the gear set is Shimano tourney. Gears are 3x7.

Does anyone know why this might be happening please? And is it something that's easy to fix myself, or should I take it to the shop for a fix?

Edit: I've not tried shifting from the medium chainring to the biggest yet, but the problem occurs consistently when shifting from the smallest one to the medium one.

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    By "drops" do you mean that you the chain is falling off the outside of the largest chainring? If so your front derailleur is over shifting - there is an adjustment screw that can be turned on the derailleur to prevent over shifting. If you got the bike from a shop it would be good to give them the opportunity to fix the issue - it should not have left the shop that way.
    – David D
    Dec 6, 2023 at 14:08
  • @DavidD I haven't tried shifting to the biggest chainring yet, but the problem definitely happens when shifting from the smallest one to the medium one. Does that also mean over shifting?
    – SRJBike
    Dec 6, 2023 at 14:57
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    This also renders my original answer useless... what exactly happens, then? Does the chain fall between the chainrings or does it it drop on the inside of the smallest chainring? Could be that it doesn't make the jump on the middle chainring because indexing is off, then it might just bounce off from the edge and drop. It could just need more tension on the cable or it could be symptom of a stretched cable if the bike wasn't new.....
    – DoNuT
    Dec 6, 2023 at 15:29
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    @DoNuT the chain falls to the inside of the smallest chainring, towards the frame. I'm new to this so I'm not sure if the chain has the right amount of tension or not, but the bike is new.
    – SRJBike
    Dec 7, 2023 at 12:10
  • Sorry I just noticed that I wrote chain tension but actually meant cable tension. In short, if the shifter cable doesn't have enough tension, the derailleur's position is off and it doesn't go far enough to move the chain on the next chainring. It'll eventually move it but if it's not enough to properly engage with the tooth profile, it will fall off and such uncontrolled movement may cause it to drop. I haven't had that on my bikes but it sure is possible.
    – DoNuT
    Dec 7, 2023 at 16:59

4 Answers 4

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I am guessing it drops to the outside of the largest chainring when going from medium to large ring, in which case it sounds like your high limit screw is set too loose. If this is not the case, ignore the rest of this answer.

Identify the correct limit screw on the front deraileur, they are often marked H and L for high and low limit.

Tighten the H limit screw until you are no longer able to shift to the large chainring. Then loosen it slowly (half/quarter turn) and check if you are able to make the shift again. Repeat until you are able to make the shift again consistently. It should then be set properly.

If you bought it new from a store you could have them do it for you. It is the safer option if it is brand new and you are uncomfortable with messing around with it.

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  • I've not tried going medium to large, just small to medium
    – SRJBike
    Dec 6, 2023 at 15:01
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    @SRJBike then the high limit screw is not the issue. Still, it sounds grossly maladjusted and I would ask the store to fix it free of charge since it was new.
    – WornChain
    Dec 6, 2023 at 15:25
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This video is a good resource if you want to try front derailleur adjustment yourself:

First thing is to assess where the chain drops. In the extreme positions (largest chainring/smallest chainring), the side plate of the derailleur should not allow the chain to move over the chainring and drop but also shouldn't touch it when you shift on the highest gear on the back (smallest cog rear vs large chainring at the front respectively vice versa).

If there is too much of a gap, the corresponding adjustment screw on the derailleur needs to be moved, the derailleur should move visually on a quarter of a turn, so watch out how it reacts and only make small increments before you try shifting, again.

Based on your comment above, if the chain drops shifting on the middle, the derailleur is probably not adjusted properly (cable tension too low), the chain will try to jump on the middle chainring, but if it isn't able to move far enough, it will fall off and it is very likely that it just bounces/drops instead of going back on the smallest chainring -> this calls for indexing as suggested in the video.

Ideally, you have a work stand so that you don't have ride around or flip the bike to verify if your change made an impact.

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Needless to say: If the bike is new from a shop and left it like that, you have every right for them to fix this at no charge.

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The chain is dropping into the gap between the chainrings.
The gap should not be big enough for the chain to drop into.
At the factory something didn't go quite right.
It is a chainring spacing problem you won't be able to resolve on your own.

This is an opportunity for the bike shop to demonstrate good customer service.

EDIT: Thanks to SRJBike's correction - the chain in falling off on the inside, next to the frame.
So, in the original post:

When shifting from a smaller cog to a bigger one in the front gears, the chain consistently drops.

When shifting from a smaller chainring to a larger chainring - shifting toward the outside - the chain falls off on the inside.

A chain that falls off on the inside is usually being shifted from a larger chainring to a smaller chainring. The derailleur has a limiting screw for the inside movement - closest to the frame, and outside movement - furthest from the frame. It seems unlikely that the limiting screws would help in this situation.

Your bike shop should fix this for free.

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  • the chain doesn't end up between the chainrings though, it ends up on the inside of the smallest chainring, next to the frame. Or are you saying it's dropping into the gap, then bouncing out and coming to rest next to the frame?
    – SRJBike
    Dec 7, 2023 at 12:13
  • @SRJBike that would be overshifting on the inside. I'll edit my answer.
    – David D
    Dec 7, 2023 at 13:47
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Newly assembled bike, as any newly assembled thing, needs to set a bit. It seems your bike is setting. It is usual, normal, standard. Some products, typically cars, are pre-set from the factory - it means they are assembled and run for designed ammount of time. Before time began, new car owners were instructed how to run the car in...

Many respectable dealers sell the bikes with "free service after X km/m and/or Y days" which is there exactly for realigning and checking everything after it sets.

So check your contract for this clause and go get the bike serviced (for "free" - you have already paid for it)

If there is no such a clause, then you are either sentenced to pay for the service or do it on your own - so go check all moving parts whether they are moving as intended.

In this particular case of misaligned front derailleur follow DoNuT's very nice answer.

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