Chain comes off large front ring when in smallest gear
Hi, I've had a read around the forums regarding a problem I've been having, but I think I've discounted most solutions....
I've recently changed my front chainset from a Truvativ Elita 53/39 to a new Truvativ Elita 48/34 to help me around the Fred Whitton Challenge (I hope!). Seeing as the new gears on the front chainset are smaller I had to move and readjust the front derailleur. On the back is a one week old (so unworn) Shimano Ultegra 6700 Cassette. I would have changed everything together but the front chainset was a little late in arriving so I changed the back first. I also fitted a new Shimano 10spd chain.
Everything worked fine until I changed to the smaller front chainset. When I am in the smallest gear at the back and the largest at the front (i.e top gear) then the chain rides off the outside of the front chainring. Shifting is fine (front or back) and the chain doesn't fall off when shifting. When riding in large front/small back then the chain ticks a bit before finally coming off. It also seems to "tip over" slightly as it comes in to contact with the front chainwheel.
Seeing that:
1. the front chainset comes as a whole assembly (bb, bearings etc) and there's nothing to adjust (it's a GPX bearing setup and no spacers)
2. the new chainset was advertised as having "9 speed rings" although I'm sure they are the same as ten speed rings- the vendor confirmed this.
3. everything is new
4. I can't see any damage to the front chainwheel
5. it doesn't come off when shifting
6. any other combination of gears is fine
7. I'm sure that the chain is tensioned correctly- I've tried removing more links than is healthy to see if the problem goes away and it doesn't.
8. there are no tight links. The chain is new and I've used a Shimano quick coupling to join it.
does anyone have any idea why the chain would come off?
I have tried two other tests:
1. I put a spacer behind the bearing cup to move the chainrings away from the frame of the bike a little. I couldn't ride it like this as attaching the left hand crank would crush the bearings, but when spinning the cranks the chain still came off.
2. I have a one month old Shimano Ultegra Chain. When I put this on it behaves better- it can take half a mile for the chain to fall off instead of just a couple of turns of the crank.
Any ideas would be much appreciated!
I've recently changed my front chainset from a Truvativ Elita 53/39 to a new Truvativ Elita 48/34 to help me around the Fred Whitton Challenge (I hope!). Seeing as the new gears on the front chainset are smaller I had to move and readjust the front derailleur. On the back is a one week old (so unworn) Shimano Ultegra 6700 Cassette. I would have changed everything together but the front chainset was a little late in arriving so I changed the back first. I also fitted a new Shimano 10spd chain.
Everything worked fine until I changed to the smaller front chainset. When I am in the smallest gear at the back and the largest at the front (i.e top gear) then the chain rides off the outside of the front chainring. Shifting is fine (front or back) and the chain doesn't fall off when shifting. When riding in large front/small back then the chain ticks a bit before finally coming off. It also seems to "tip over" slightly as it comes in to contact with the front chainwheel.
Seeing that:
1. the front chainset comes as a whole assembly (bb, bearings etc) and there's nothing to adjust (it's a GPX bearing setup and no spacers)
2. the new chainset was advertised as having "9 speed rings" although I'm sure they are the same as ten speed rings- the vendor confirmed this.
3. everything is new
4. I can't see any damage to the front chainwheel
5. it doesn't come off when shifting
6. any other combination of gears is fine
7. I'm sure that the chain is tensioned correctly- I've tried removing more links than is healthy to see if the problem goes away and it doesn't.
8. there are no tight links. The chain is new and I've used a Shimano quick coupling to join it.
does anyone have any idea why the chain would come off?
I have tried two other tests:
1. I put a spacer behind the bearing cup to move the chainrings away from the frame of the bike a little. I couldn't ride it like this as attaching the left hand crank would crush the bearings, but when spinning the cranks the chain still came off.
2. I have a one month old Shimano Ultegra Chain. When I put this on it behaves better- it can take half a mile for the chain to fall off instead of just a couple of turns of the crank.
Any ideas would be much appreciated!
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Comments
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'Tis odd and sounds like a chain line issue that you've already tried to rule out with the spacer in the BB. Have you tried it with the front mech completely removed to rule out the mech pushing the chain out and off the ring?0
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Hi ME-109. Yes I have! I've also checked that the chain is on the right way around (Shimano chains are directional). Perhaps I could try a different make of chain to see if its any better....0
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Did you shorten the chain... ? your chain might be a bit slack now! You probably need to remove a couple of linksleft the forum March 20230
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Limit screws?0
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When you are on the big ring and smallest sprocket the chain line is slightly to the outside of the chain-ring. This being the case if the height of the front DR is not spot on the chain can jump off to the outside. Try lowering the front DR so that the outer plate only just clears the outer ring. That way the outer plate of the DR acts as a chain catcher.0
