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Old 01-14-13, 05:50 PM   #1
escarpment
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problem tuning gears

I am running a mutt setup and am having trouble dialing it in. I have a single 39t chainring in the front, the chain is ramped because its off a tripple. Its a 7 speed, with an stx in the front that doesnt always catch. I have taken it apart as much as I can, regreased it, retightened it also. I have an ultegra 10 speed body with a cage that I stole from an stx RD. I actually had to drill a new hole for the cage spring to sit in. But the tension and function seem to be normal.

Basically no matter where I set the limits, the RD wont line up with the 2nd and 3rd cog.

I was under the assumption that all modern shimano derailleurs had the same pull ratios.

Does anyone think its just the shifter falling out of index



The chain/cassette/ and derailleur pulleys are all relatively new.

The cassette and chain are both the basic sram 7 speed models.


Thanks.
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Old 01-14-13, 05:57 PM   #2
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Is your bottom bracket spindle length such that the chain ring is more or less centered with the middle of the 7 speed cluster?
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Old 01-14-13, 06:03 PM   #3
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yes, yes it is, I was wondering if it just had to do with cross chaining of sorts.

I was thinking if I got a say an 8 or 9 speed chain that is thinner I would have less problems.
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Old 01-14-13, 06:03 PM   #4
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2nd and 3rd where 1 is the largest and 7 is the smallest?

is the derailleur cage parallel with the sprockets ?
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Old 01-14-13, 06:05 PM   #5
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yes the cage is parallel, 2nd smallest, 3rd smallest, is what I ment.
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Old 01-14-13, 06:12 PM   #6
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so its aligned in all the other gears? 1st (LARGEST as thats the low gear), 2,3,4, and 7 (smallest and highest gear) ? of course, 1 and 7 are controlled by the set screws, so really only 2,3,4 would be indexed, and 5,6 are out of whack ?


using a 7 speed SiS shifter with a 10 speed derailleur (even with the cage transplant) is certainly novel.
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Old 01-14-13, 06:15 PM   #7
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Well I had a ultegra RD that had the cage bent in an accident, The old RD on my bike was a deore dx that weighed about a pound.

Let me ask you this, do you think it is the derailleur, I had the same problems with the old one.
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Old 01-14-13, 06:35 PM   #8
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ah, given that two derailleurs had same problem, that leaves the shifter.
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Old 01-14-13, 07:28 PM   #9
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First you need to make sure that all the little details are correct. Like is the upper pulley the proper SIS (with the float) one. Is the der cable anchored properly (and the little plate is not turned 90* off). How's the cable friction through the casings.

But you do display one of the problems with running a "system". When a couple of the eliments get changed things might not work the same. Shimano, back when SIS was first being introduced, has said there are 17 different aspects to a properly speced SIS system. And that was with down tube levers.

A few comments- "Basically no matter where I set the limits, the RD wont line up with the 2nd and 3rd cog." Why do the der limits have anything to do with the cogs between them? In between the limits the issues are cog spacing, pull ratio (see cable anchor and spec compatibility), bent and twisted parts, wrong pullies, cable friction, chain width, and the like. Shifters don't just "fall out of index". they get bent/twisted, fixed the wrong way, have miss anchored cables, get stiff pivots, (and more) but something from the outside has to effect them.

If i had the bike in the stand i would work from the lever and back through the cable to the der and cogs. Seperate out each from the rest and check their movements and actions. If all seem to be working seperate of each other then I'd sub in parts. First being the cable/casing because it's the cheapest and gets worn/gritty/kinked easily. Next would be the rear der because it's the part that's most easily damaged and/or worn. If an experienced eye can look at the set up they might be able to give more advice. Andy.
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Old 01-14-13, 08:20 PM   #10
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Quote:
Originally Posted by pierce View Post
ah, given that two derailleurs had same problem, that leaves the shifter.
Could the hanger have been bent in the accident the OP describes as damaging one RD, would that cause the skipping on only a few of the gears???
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Old 01-14-13, 08:24 PM   #11
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he says its parallel, that was my first thought too.
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Old 01-14-13, 08:34 PM   #12
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The single chainring centered in the chainline lined up with the middle rear cog .. #4 of 7 .. ?
same plane, parallel to the bike centerline ?
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Old 01-15-13, 01:23 AM   #13
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Well I believe I have solved the problem, The issue stemmed from 2 things as I see it. First being the top pulley, And the cassette. I had 2 bottom pullies in the cage, luckily I had a top lying around. So once I got that fitted the chain skip seemed to stop, I checked the indexing without the chain and everything seemed to line up. Untill the Lagest 2 cogs. Once there I could no longer get clearance and the derailleur would get hung up on a cog. I was like a 12-32. I dont think the derailleur could hangle the big jump in the last 2 cogs. I had an old hg cassette and cleaned it up. threw it on also. Threw on a 8 speed chain. And viola. Well it still gets hung up on the last 2 cogs but I dont really plan on using them.

Thanks for the help
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