Cervelo R2 Chain dropping and Index issues (di2)

jon33

Hi

I have a 2015 Cervelo R2 that I've upgraded to Ultegra di2. I have a couple of issues I'm hoping someone can help me sort out.

1. Gear indexing, this should be simple (and was on my old Foil). But no matter what I do I'm having the issue where the rear derailleur will move but the chain won jump to the next cog, I'm thinking the hanger may be misaligned but the I noticed that when using the quick release to hold the rear wheel in place the frame/hanger seems to bend round depending on how tight it is. Can anyone advise on what to do with this? Should I check the hanger alignment once it's clamped in or...?

2. Chain dropping, the bike has a FSA Gossamer crankset and something I've noticed is the chain drops off quite a lot (usually off the big ring). Happened on mechanical and with the di2. The upper/lower limits on the from derailleur are set correctly.

The only difference between this and the Foil that I had set di2 up on before (apart from the frame) is that I'm running a 11-32 on the Cervelo, whereas the Foil had a 11-28; would this account for any differences in performance I'm noticing?

Thanks

The Rookie

jon33 wrote:

I noticed that when using the quick release to hold the rear wheel in place the frame/hanger seems to bend round depending on how tight it is.

Not uncommon, and unless you do the QR up the same (or similar enough) each time you'll have to re-do the indexing every ride, so first step is to make sure its tight every time you use it, not hard as there is no need to touch the nut, just flip the QR lever. You could even threadlock the nut in place.

jon33

The Rookie wrote:

Not uncommon, and unless you do the QR up the same (or similar enough) each time you'll have to re-do the indexing every ride, so first step is to make sure its tight every time you use it, not hard as there is no need to touch the nut, just flip the QR lever. You could even threadlock the nut in place.

Thanks for that reply, could it be that when I've had the shop straighten up the hanger they've straightened it when the QR was at a different tightness so it's slightly off when I'm doing it which could cause the indexing problems?

Monty Dog

Only straighten a hanger with a wheel inserted / QR closed or you could bust the mech hanger - any competent mechanic would know this. Also check that the retaining screws are tight.

jon33

Struggled to get a pic in the dark last night but I checked the chain ring and this is the big chain ring after about 800 miles, should it be this worn already? I'm thinking this could be the reason it's dropping?



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svetty

Chainring is fine. Assuming you are correct that the outer limit stop is indeed correctly adjusted, the other obvious thing to check is that the mech cage is set to the correct height. I generally try and run it as low as possible - a mm or two above the tallest teeth on the big chainring.

jon33

Svetty wrote:

Chainring is fine. Assuming you are correct that the outer limit stop is indeed correctly adjusted, the other obvious thing to check is that the mech cage is set to the correct height. I generally try and run it as low as possible - a mm or two above the tallest teeth on the big chainring.

Thanks, I'll double check that tomorrow, however I've only just reset the height/alignment using the Shimano instructions so I think it's going to be the right height. The only problem I can see there is that some of the teeth a 2-3mm shorter than the others, I've set the height based on the longest ones.

Edit: The only other thing I had thought of (Not sure if you can do this) is put a spacer between the rings and the frame to move the rings out slightly as maybe the di2 thinks the rings are wider than they are? :?:

jon33

It's bugging me so I went out and checked tonight, that's as low as it goes, you can see the difference between the teeth length but it looks okay for the longest?

I've actually convinced myself that it's the hanger now that's the issue. It was apparently realigned but I'm not convinced, the rear shifting is terrible for what I'd expect - the pic doesn't look too bad but I can see that it's not parallel.

mikenetic

The teeth on outer chain rings are machined at different heights to help with the pickup on the shift. Those low ones are just behind a pin (the circle you can see) that also helps lift the chain from the inner ring. The lower teeth means the chain hops onto the ring more readily.

jon33

mikenetic wrote:

The teeth on outer chain rings are machined at different heights to help with the pickup on the shift. Those low ones are just behind a pin (the circle you can see) that also helps lift the chain from the inner ring. The lower teeth means the chain hops onto the ring more readily.

Cool, didn't know that. Could the alignment on the rear derailleur be throwing it off the front as well- maybe if the chain is slightly twisted? (hoping for an easy fix!)

keef66

Monty Dog wrote:

Only straighten a hanger with a wheel inserted / QR closed or you could bust the mech hanger - any competent mechanic would know this. Also check that the retaining screws are tight.

I can't imagine doing it without the wheel inserted / clamped. What would you check the alignment against if not the wheel rim??

jon33

I've ordered an alignment tool which should arrive tomorrow, hopefully this will sort the indexing issue.