Chain drops when shifting up a gear at the front?

Question

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.

Answer 1

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.

Answer 2

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.

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.

Answer 3

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.

Answer 4

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.