I have a brand new Cervelo P3, DI2. I put a chain catcher on the front/crank. A couple of times the chain has still come off on the front gear. No sudden shifting or some other extreme thing - just normal riding. The DI2 has been professional adjusted. The catcher stops the chain from “jamming” in between the gear and the frame bottom bracket area at the top. The catcher catches the chain, but the chain still is off at the front of the gear area, rubbing against the carbon frame. NOT GOOD. So far no major scratches in the carbon - but little scratches - NOT GOOD. The last time the chain came off, the catcher caught the chain, but the chain kind of wrapped around under the gear and really got jammed between the gear and carbon. ESPECIALLY NOT GOOD. scratched the fame good. I use Squirt “dry” lube on the chain - never a problem before on other bikes.
HELP. What’s going on here? How can I keep that chain on the gear? and not get jammed on the carbon? Is this a problem with Squirt dry lube? Is the tension on the chain not enough, so that the bottom of the chain (under the bottom bracket) sort of flops around and wedges between the frame and the gear? or what? I don’t want a scratched/gouged carbon frame on a brand new bike. Thanks
Since this is a brand new bike with a brand new drivetrain, the problem has to be adjustment. I almost never get chain drops, except when I had an adjustment problem or an issue in the RD that would not capture the slack during the shift. The limit screw is probably off, and the FD trim is probably off.
Another possibility is the chain length could be off.
Does the chain drop when the chain is on a particular cog in back? Is there a range in back that the chain drop never occurs
This is Shimano’s old guide toward chain sizing. It is not applicable to their new Shadow derailleurs, but it will give you a rough order of magnitude. When you chain is on the big chainring and smallest sprocket, are the two pulleys on the RD in a vertical line?
Bring it back to the person who built the bike.
You should not need a chain catcher at all.
Thinks to check in rough order of likelihood:
FD tuning
FD limits
Proper FD mounting (height, angle).
Damaged (bent) FD
Proper chain length
Excessive chain wear
Damaged or bent link in the chain
RD hangar alignment
RD tuning
RD limits
RD chain tensioner not working properly
Damaged RD
Excessively worn chainring teeth
Wrong type of chain
Wrong type of chainring
you can cross off RD hangar alignment, else a new frame is needed since it is integrated with the frame
.
Bring it back to the person who built the bike.
Hopefully the builder was just in a rush or made a blooper.
Otherwise, they are incompetent and if so, the last thing you want is for them to have another whack at it.
To the OP…
Trail had a great list. Shift into the big ring/small cog and check to see how the FD cage sits relative to the chain. Then do the same with small ring/big cog. There should be very little room within the cage for the chain to escape off into the bike. I think shimano says 2mm?
Is the cage parallel with the rings?
Is the FD loose? Can you wiggle it with your fingers or is it locked down?
There should be very little room within the cage for the chain to escape off into the bike. I think shimano says 2mm?
New Di2 is very tight…
Shimano’s spec is 0.5mm - 1.0mm between chain and outer FD plate when on the big chainring and small cog.
Spec is 0.0mm - 0.5mm between chain and inner FD plate when on the small chainring and big cog.
So which chain catcher did you put on? If a derailleur hanger mounted one did you remove the entire derailleur to get it on? If that is the case you might of screwed up the alignment of the derailleur ever so slightly and could be the cause of shifting issues.
So which chain catcher did you put on? If a derailleur hanger mounted one did you remove the entire derailleur to get it on? If that is the case you might of screwed up the alignment of the derailleur ever so slightly and could be the cause of shifting issues.
Bingo. I bet you nailed it.
OP: If you removed and reinstalled the FD to install a chain catcher, there is a likelihood that you misaligned the FD upon re-installation. Per recommendations above, I would remove the catcher from the bike. Then, the diagrams below illustrate Shimano’s instructions for FD alignment. The outer plate must be 1mm - 3mm above the large chainring. And, the outer plate must be exactly parallel to the large chainring.
actually, during the initial shop build, I had the builder/mechanic install the chain catcher - so I think it was placed properly and the front derailleur didn’t get moved out of the way.
THANK YOU to everyone who took the time to write something about fixing this problem. I will take the bike back to builder and get them to look and adjust - armed with the information in this thread. Thanks
I had same issue at first with a 2016 P3 using di2 - it was a FD problem. Once FD was fine tuned properly all was fine and haven’t dropped a chain now in 2 seasons,