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Shadow Der on KM chain rubbing issue

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Shadow Der on KM chain rubbing issue

Old 05-18-16, 07:20 PM
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Rotten 
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Shadow Der on KM chain rubbing issue

I built my Karate Monkey from the frame up and made it a 1x10 with a Zee derailleur, shimano 11-34 cassette, and XT shifter.

Rode it last season, 99% paved road. Slowly getting stronger and occasionally using the 11t cog on the downhills and easy flats. Before putting it away I began to notice that getting it to the 11t took some force and was markedly louder than other shifts.

Long story short this year I decided to install a 11-36 to replace the 11-34 and discovered that when shifting down to the 11t the chain would bind against the B pivot (pretty sure that's what it's called). I could get it to complete the shift with extra force on the pedals but that's unacceptable. I did switch the cassettes back and discovered it does it with the old one as well.

I really like the Zee but is its shadow design causing the interference? The bike has never been crashed or layed over. If it's the shadow design, is there a quality non-shadow 10 speed rear derailleur even being made anymore?

Thanks for your time.
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Old 05-18-16, 11:03 PM
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You need to identify the actual interference, if any. Then decide if another der would have a lack of material at that spot.

But I'll talk about der design and shifting in general which might bring insight. One of the keys to shifting response is to minimize the amount of chain that is between the guide pulley and the cassette cog's underside. The more links of "open chain" that are between the pulley and cog the more over movement of the der is needed to compensate for the greater slop of more links. The Shadow ders have the guide pulley coaxial with the cage pivot. So unless the der's parallelogram is slanted at the same angle as the cassette cogs size progression this open link gap will vary. IME this open gap/links between cog and pulley grows with shifting to smaller cogs. The der cage/pulley designs of only a few years ago had the guide pulley off set from the cage pivot in a manor which allowed the pulley to rotate up or down and add another movement to keep the gap minimal. Andy.
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Old 05-18-16, 11:21 PM
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Despite your statement that the bike never fell over, I suspect that the hanger may be bent inward slightly.

I assign this the same weight that police investigators do to spouses when investigating a murder. It's simply the most logical place to start.

The placement of the lower pivot makes Shadows especially sensitive to hanger alignment because it pushes the pivot into the line of action. I do have one question though ---- after the initial setup, did you at some later time readjust the upper or lower limits?

Try this diagnostic which you can do with a friend. besides the friend, you'll also need a broomstick and 2 beers.

Shift to high (11t) and lean the bike close to vertical against a wall. Have your friend stand the broom stick (or yardstick or any straight edge) vertical against the rear tire as a reference, while pulling the lower chain loop forward so the RD cage is pretty vertical (no precision or plumb needed). Now, squat behind the bike and eyeball the cage to see it's parallel to the reference. It should be, but I suspect you'll find the bottom closer. If so, put a hex key into the upper pivot bolt (the one in the frame) and grab the RD body and using the key nudge it up and out a hair then check your work. As you do so, the lower pivot should move outward and clear the chain.

If/when you finish and it's working again, open both beers and hand one to your friend as a thank you for the use of his hands.
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