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Shimano 6870 Di2, Rotor Q-Rings front shift problem

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Shimano 6870 Di2, Rotor Q-Rings front shift problem

Old 05-16-15, 02:24 PM
  #1  
Hinge
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Shimano 6870 Di2, Rotor Q-Rings front shift problem

I just installed the complete 6870 Di2 system on a Look 585 carbon frame. The frame is quite small. Rotor crank with 50/34 Q-rings. KMC X11SL chain. Previously I had 6800 front/rear derailleurs & shifters. Everything worked great. The 6870 install went quite smoothly. I followed the dealer manual to the letter. On the stand the shifting is flawless.

However, when I ride the bike it simply WILL NOT shift from the small ring to the large ring when in cogs 5-7 in the back. If I loosen the high limit screw enough to solve the problem, it will frequently throw the chain to the outside. The cage is absolutely as vertically close as possible to the large ring. The high/low chain/cage spacing is dead on. I have tried all of the different trim settings. I have tried the 2 different FD spacers that Rotor offers. However, these make the support screw unusable. I have tried angling the derailleur a bit so the rear of the cage is slightly outboard. Slight improvement but not enough..

I notice that after initiating the shift from the small to the large ring and while the chain is scraping away at the large ring, trying to move up, if I hit the left shifter again, it will move slightly outboard enough to get the chain to catch and shift up. I have seen no reference anywhere to this other, secondary shift position, is this normal? It is sort of a remedy but I really don't think I should have to basically shift twice to get it to work. Especially not for what this system costs! It would be nice if the FD would move enough on the first press of the shifter switch to complete the shift.

I don't have the PCE1 so I don't know what firmware version is installed. The parts were all bought new very recently.

I would do a complete reset and start over if I could find a way to do that. Anyone know?

Sorry to be so long winded. I am open to any suggestions. I'm hoping to find some solution this weekend so I won't have to wait until Monday to call either Shimano or Rotor.

Thanks in advance for any input.
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Old 05-16-15, 04:16 PM
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Two possibilities come to mind, one easily fixed, one not so. If you're lucky, it's a matter of the FD not being aligned spot on. You can also, sometimes, improve upshifting by bringing the heel in (toe out) so first check, then try tweaking the alignment.

Otherwise, I suspect that your chainring separation is slightly greater than the programmed FD travel, so it's not moving quite far enough. You might try fooling it bringing the low gear limit out a bit more, right to and just shy of where the chain rubs in low. Starting from a bit father out, might be enough to make the shift. Otherwise, double check the chainring separation and compare to original Shimano, and if necessary, find a way to bring them closer together.

BTW- I'm not 100% familiar with Di2 shift protocols. I know it auto trims when the chain is on the inner cassette sprockets, but don't know if it shifts full span then trims, or shifts based on the trim position. If the latter (and I hope not), it'll be hart to upshift when on the inner few rear sprockets.

You might try moving the chain out of the way so you can shift without turning the cranks, and gently feel the travel pattern to see if it shifts out and trims back, or just shifts to the trim position.
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Last edited by FBinNY; 05-16-15 at 04:32 PM.
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Old 05-17-15, 12:36 PM
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FB,

Good ideas. Angling the rear end of the cage out slightly does help a bit, especially with the trim since the chainstays are a bit on the short side.

I need to measure the chainring separation. That would make a lot of sense if it was slightly wider than Shimano. However, I hear quite a few people having good luck with Di2 and Q-Rings. Regardless. I'm going to look into that right now.

Thanks
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Old 05-17-15, 01:36 PM
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I wonder what Rotor said when you asked them.
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Old 05-17-15, 03:45 PM
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AnkleWork, I am going to call them tomorrow. I'll report back.

BTW, I took the bike to a shop to check if firmware updates were available. Everything except the junction box A needed an update. The update completed successfully but I haven't noticed any change in shifting behavior. Scratch that, there is one change that I can notice. There is now a 2-3 second delay before it will let me try that secondary outer shift position I mentioned in the OP. Not sure I'm happy about that, but ideally, I shouldn't even need that function.

Last edited by Hinge; 05-18-15 at 12:17 AM. Reason: fixeses
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Old 05-21-15, 01:45 PM
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I had a nice chat with Rotor. They were very helpful. I came away with 3 suggestions: 1. insure the chianline is correct (43.5mm) 2. check for spacers between the drive side crank arm and BB 3. lengthen the chain.

The chainline is correct on the bike, and there were no spacers present. I did add two links to the chain and that seems to have helped a bit. I'm going to keep working on it.
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Old 05-21-15, 04:14 PM
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Not quite the same problem, my Di2 (factory installed) shifts fine but throws the chain off the cranks very frequently. At first I thought it was me but after a ride where it happened three times, I'd had enough. Called several local shops that I know had experienced professional mechanics and got a consistent answer: to avoid shifting problems with the Di2 both FD and RD must be properly aligned and that I should learn how to do myself because it will need it more often than mechanicals. Worked - so far.
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