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Trek Madone 7.9/Di2 -- sloppy front shifts

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Trek Madone 7.9/Di2 -- sloppy front shifts

Old 05-20-20, 10:34 PM
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bobonker
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Trek Madone 7.9/Di2 -- sloppy front shifts

Hi there,

I have a 2015 Trek Madone 7.9 with Dura-Ace Di2. The bike came to me with a SRAM (Quarq) crankset with 50/34 rings, but original crank was included. The front shifting was clean and crisp.

I swapped in a Dura-Ace 9000 50/34 crankset (so it'd all match) and can't get the front the shift cleanly. Sometimes the chain will "struggle" to get onto big ring. The problem worsens as the chain is further up the casstte. The main issue seems to be that I can't get the derailleur low enough. The SRAM rings had teeth with a higher profile, so the front D cage rested just above the tallest tooth. With the front D down as far as it will go, the distance to the tallest tooth with the D-A rings is significantly more. The low and high limits have been reset per Shimano's specs.

My options seem to be:
1. Quit being a wuss and run 53/39 or 52/36 rings. Not a great option since it's really hilly here.
2. File the front derailleur hanger -- not overly appealing.
3. Use a custom front derailleur bolt. Ie, machine off the threads and possibly a bit more in the area that contacts the derailleur hanger.
4. ?

Thanks,
Bob
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Old 05-21-20, 02:45 AM
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there are some products designed for this problem https://wickwerks.com/products/fit-link-adapter/ although maybe the file depending on how much material you have is a viable option, I assume you dont want to run the sram crankset, so option 4 could be to change the rings to a semi compact 52/36
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Old 05-21-20, 07:30 AM
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When the ft der was repositioned down did the anti twist set screw still contact the little tube protecting tab? If this is an question you don't understand you need to do more study on install instructions of take the bike to a shop that knows about the newer gen. of Shimano BO ft ders. Andy
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Old 05-21-20, 09:30 AM
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Originally Posted by Andrew R Stewart View Post
When the ft der was repositioned down did the anti twist set screw still contact the little tube protecting tab? If this is an question you don't understand you need to do more study on install instructions of take the bike to a shop that knows about the newer gen. of Shimano BO ft ders. Andy

Hi Andy,

Thank you for the responses and link. I'm quite familiar with the twist screw/tab. I took the derailleur completely off this morning and found that the tab is no longer there! The set screw is pretty close to the frame, so it must've been there at some point. Job #1 will be getting a replacement. Hopefully the LBS has it in stock. I have a pile of front derailleur bolts, so I think I'll machine one down and see how that goes (in combination with the tab being replaced).

Bob
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Old 05-21-20, 05:07 PM
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Using a combo of a thinner bolt and little filing on the derailleur hanger, I was able to get the derailleur down so that there's ~1.5mm of space between the cage and closest tooth.

I got and installed the missing back plate and turned the set screw so that it just touches it. Set the low and high limits. Here are 5 shifts. Only #3 is "clean". The cassette and chain are new. Crank has unknown miles on it. Is there anything else that I can try before I replace the chainrings?

https://www.youtube.com/watch?v=dIxM...ature=youtu.be


Thanks,
Bob
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Old 05-22-20, 03:03 PM
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Update:

The situation has much improved. After setting the low and high limits, I did the big-big combo and adjusted the trim. I moved the front derailleur outward as far as possible. Unfortunately, I'm still about 2-3mm away from the chain but it is shifting much better and more consistently than before.


Bob

Last edited by bobonker; 05-22-20 at 03:16 PM.
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