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Old 07-27-05, 02:07 PM   #1
shabbis
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I recently swapped out my DA 11-23 for a DA 12-27 and have a couple questions/issues (I have posted pictures to assist with the questions):
1. Will I need a longer chain? (It doesn't seem like I do, the chain appears to have enough bend in the RD when in big/big, picture #3).
2. I cannot seem to get the FD and RD just right, do I just keep messing with the limit screws? Any tips on this would be great (I looked at the Park Tool site already).
3. Any tips on fine tuning to make it flow like the 11-23?

I didn't think going from 11-23 to 12-27 would make that much of a difference to the point of having to adjust the FD and RD.

39x27

39x27

53x27 (big/big test)

53x27 (big/big test)



Last edited by shabbis; 07-27-05 at 02:51 PM.
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Old 07-27-05, 02:31 PM   #2
jazzy_cyclist
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What symptoms do you get when you say "not right"? I'm not a wizard mechanic, but the limit screws only affect how far you can push the chain to the inside or outside, not how it performs in between.

I would have thought that you'd need a longer chain, although maybe it's not that dramatic a change.
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Old 07-27-05, 02:47 PM   #3
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1. I am having a hard time getting the FD to line up at the extremes, when in 39x27 and when in 53x12. Seems to rub at both ends, this was not the case with the 11/23, which doesn't make sense to me as the size of the cassette is the same.

2. I compared the 3rd picture in my post with the pictures on Park Tools site and it seems like the chain is long enough (never really noticed how close the RD sits below the cassette, basically opposite the gear on the chain). There appears to be enough bend in the chain thru the RD when in the big/big (53x27) position.

3. The rear cassette seems to rub slightly when pedaling.

I hope that's enough detail.
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Old 07-27-05, 03:13 PM   #4
Jim Bonnet
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I do this similar swap often and never have to adjust the der.

Further, you should NEVER go big/big, do the math, with 20 speeds someplace in the range you should have the same gear ratio and not have to torque your dura ace der.

You shouldnt have to adjust your limit screws. Was there a spacer in the box with the cassette?

my .02
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Old 07-27-05, 03:15 PM   #5
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Quote:
Originally Posted by shabbis
1. I am having a hard time getting the FD to line up at the extremes, when in 39x27 and when in 53x12. Seems to rub at both ends, this was not the case with the 11/23, which doesn't make sense to me as the size of the cassette is the same.

2. I compared the 3rd picture in my post with the pictures on Park Tools site and it seems like the chain is long enough (never really noticed how close the RD sits below the cassette, basically opposite the gear on the chain). There appears to be enough bend in the chain thru the RD when in the big/big (53x27) position.

3. The rear cassette seems to rub slightly when pedaling.

I hope that's enough detail.
well, if you have been to the park site, you should know the drill on derailer adjuatment.Start at the beginning. In most cases the change should have required nothing but a possible tweaking of the B tension screw(first pic, the jockey wheel looks too close to the big cog.).Nothing with respect to the FD should have changed.

Last edited by sydney; 07-27-05 at 03:20 PM.
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Old 07-27-05, 03:18 PM   #6
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Sydney, as always, is on it.
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Old 07-29-05, 06:50 PM   #7
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sydney, ive a problem, ,my rear deraileur touches my 23 cogs on the rear, the b screw is full adjusted in the way and still clicks and rubs. what to do my man?
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Old 07-30-05, 12:28 PM   #8
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I have set up my DA 12-27 exactly per Shimano's manual and it works fine. The B-screw is probably the right tip. Careful when it's too close to the sprocket, I have read you can kill a cassette that way. And DA 7800 is not cheap.
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Old 07-30-05, 03:47 PM   #9
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that chain was sized for a different size sprocket. now u put back on the same chain. it has to be the chain limiting the situitation. bigger cogs, biger chain. ur chain doesnt travel any further left towards the big cos, it just traves higher and stuff. try getting a few links. if im wrong, im sorry
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Old 07-30-05, 04:57 PM   #10
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How many miles on the chain? If you put a worn chain on new cogs (reverse of the most common mix) I doubt it would run "smoothly".
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