reqm

I recently put together a new bike, and everything seemed to work well for a few weeks until recently.
The chain would drop quite frequently when I shift from the small ring to the big ring (it would drop about 1 out of 10 times). Not only that, the chain would get jammed between the small ring and the frame, making it impossible to get it out without a quicklink tool. The mechanic told me that certain cranksets cause the chain to get jammed this way. The problem seems to be happening both indoors on the trainer and outdoors.

Has anyone experienced this or know of a solution?

Specific bike info:
Cervelo R5 (2018) size 48
Dura Ace R9100 (mechanical) RD, FD, and shifters
Rotor 3D+ crank, compact Qrings
Ultegra R8000 chain and cassette

Are there any incompatible parts here that I should try swapping out for another?
My previous bike was a size 51 Cervelo with the same setup, except it was 10 speed. Never had any issues, and the chain never got jammed even when it did drop.

cny-bikeman

It makes little sense that the chain would end up between the small ring and the frame after shifting "from the small ring to the big ring." If it's actually the reverse, then the simplest solution would be to purchase a chain watcher. However the proper 1st thing to try is to mount and adjust the front derailleur, following Park Tool's procedure from start to finish. It not only will reduce occurrences but may improve your shifting overall. Actually, that's the absolute 1st thing to do if your post is accurate, because it means that the shifting to the large ring is totally unacceptable. Also make sure you do not have too large a difference in size between your two chainrings.

Dan Burkhart 

I'm sure there is some adjustment issue going on there, but in the meantime, here's a doodad that guards against this happening.
Deda Elementi Dog Fang (Chain Catcher) | Chain Reaction Cycles

dsbrantjr

+1, I use these: N-Gear, Home of the Jump Stop Not as a Band-Aid against sloppy adjustment, but more of a "belt and suspenders" approach because I hate digging a greasy chain out and re-railing it.

DrIsotope

The FD is out of adjustment. Either the cable has stretched a bit, or the FD itself got bumped/knocked out of position.

jimincalif

In addition to checking derailleur adjustment, check to see that the FD is not bent in any way. Also check your crank installation to make sure there is no lateral play, this can wreak havoc with shifting.

reqm

Thanks for all the helpful input so far! The issue always occurred when shifting from the small ring (34) to the big ring (50).
I've had my go-to mechanic (he's well known in the area and high in demand) adjust the derailleurs each time it got jammed.. 6 times in 3 weeks. I've always had a chain catcher installed and tried 2 different brands (Rotor and one other brand I cant recall), but it didn't prevent the chain from dropping not even once.

I'll ask him to check for lateral play or if the FD is bent/out of position. Really hope to fix this soon as it's been a frustrating experience with the new bike

shelbyfv

The factory builds seem to use 9100 cranks, was there a reason you didn't want those?

DrIsotope

Now knowing that the FD has been adjusted by a mechanic more than once, I'll go out a limb and say there's a fair chance you're gonna need a new FD. I had the chain catch on an FD-6700 and slightly tweak the shape of the cage-- it was never the same. I could kinda bend it back with my thumbs, but it would catch again and again. The only fix was replacing it.

Cervelo does it both ways. My R3 came with the full 6800 group, but a Rotor 3D crankset. Though I don't know if I've seen the 8000 group with Rotor. I just assumed that the 6800 crank wasn't made in a BBRight version.

reqm

I wanted to make the new bike as identical to my old one as possible since the previous build seemed to work well.

u235

Had the same exact issue and result. I was able to play around and tweak it to where little to big worked but big to little had to be done manually. I took the advice of someone around here and went with a new one.

xenologer

Try a different mechanic

If it takes him 6 tries to continue failing....

reqm

Thanks for sharing your similar experience. I'll try replacing the FD next.

The other issue is the fact that the chain gets totally lodged between the small ring and the frame.
It's really inconvenient since nobody carries around a quicklink tool on a ride, and it can't be good for the frame either. Is the small size of the frame to blame? Or could it be the crankset?

The Cervelo + Rotor combo worked fine on my previous bike (older model that was a size bigger).. never had a chain jam issue with that setup before and there seemed to be more clearance in that area.

hambaki

I have trouble with the same problem with Cervelo R5 as well. Even more I heard about it from other man who have this problem on his bike, cervelo R5.

If you fix this with some tips, please let me know.

Or If it couldn’t be fixed with any effort, we could ask Cervelo to solve this problem by publicizing.

Feel free to reach out.
My email adress is as below.

hambaki86@gmail.com

tankist

Somewhat related - I had the same problem with Orbea and SRAM eTap Force AXS. Solved (hopefully) it by adjusting FD 3 times, including inner limit screw. SRAM documentation and video were really helpful.

Alexssandro_BSB

"My previous bike was a size 51 Cervelo with the same setup, except it was 10 speed. Never had any issues, and the chain never got jammed even when it did drop.[/QUOTE"


really my comment has no relation to your problem, we do not have the same setup nor the same bike.

but I had the same problem. in my case the carbon was soft and could not adjust in FD.