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Shifting Problem

Old 05-17-14, 05:51 PM
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Roadie1
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Shifting Problem

Hi Everyone:

I am riding a bike I recently did a restore/upgrade to. It is a 1987 Trek 400. I upgraded the bike to Microshift 9-Speed Brifters and Derailleurs with a Wheels Manufacturing 12-25 cassette and a KMC 9-Speed chain. Eventually I plan to replace the shifting components to Campy but for now the Microshift is getting it done very well. I am just now starting to put regular miles on my bike and so far I am very happy with my project.

The problem I am having is with the chain being slightly mis-aligned in only certain gears. I ride primarily in the 15, 17, 18, and 19 back cogs which is the center of the cogset. Those cogs shift spot on with no rubbing or rattling but when I shift higher or lower than these cogs I get a slight chain rubbing. From playing with the rear shift cable when I hear the rub it appears that the chain is moving a bit to far towards the outboard side of my bike when I shift. I can tension the rear cable just slightly with my hand and the rub goes away.

The frame is true, the chainline is good, the rear drop out is aligned, everything I can think of is spot on. I know there is a small difference in the width of the Shimano vs SRAM chains and a corresponding difference in the cog to cog spacing between the two but generally with a little care I can get one dialed in to work on the other groupset with no problems. Is it possible that the KMC chain is perhaps wider or narrower than the Shimano and SRAM and thus causing this problem? Any input is appreciated. Thanks.
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Old 05-17-14, 05:58 PM
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OK you need to examine and describe the problem more precisely.

You might have hat I call "spanning error".

Picture this. If every click pulls a hair too much cable, and you optimize trim for the middle of the cassette, the error may be minimal near the middle and get worse as you move farther to either side. The key would be trim offset ie. toward the middle as you move in either direction (not enough travel), or the opposite, trim offset away from the middle (too much travel).

Once you identify the nature of the error, you can look for a fix.
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Old 05-17-14, 08:09 PM
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You've described a scenario where shifting all the way out is going slightly too far so I'd suggest adjusting the high gear limit screw - (H) - sorry if this is terribly obvious and you've already covered it, but it does sound as if the derailleur hasn't been properly set. There's no way it'd shift too far out this way if it was set correctly.

Same would apply for the Low limit screw -- enough so it just shifts into the big sprocket and maybe half a turn more.

It's my understanding that Microshift, SRAM and KMC make Shimano compatible parts, which presumably makes them compatible with eachother -- personally, I'd rule out incompatibility. The last possibility is just that the derailleur cage is bent, or in some other way it's slightly off the plane of the cassette cogs.

Hopefully this makes some sense and isn't already something you've tried.

Last edited by flangeflange; 05-17-14 at 09:32 PM.
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Old 05-27-14, 07:02 PM
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I believe I have fixed my problem and it has to do with the remarks made by FBinNY. When I bought my wheelset the guy threw in a cogset that wasn't what I would ride in the area where I live. I live in a very flat area and the cog set I got with my wheels is a 12 - 32 9-speed SRAM cog set. Wanting to ride my bike I went ahead and set it up knowing that I was replace it at my first opportunity. The SRAM cog set is the one I was having shifting troubles with.

I bought and received a 10 - 23 Ultegra 9-speed cog set from Cambria Bike (can't say enough good about these guys!) put it on my wheel, dialed it in and my shifting problem is gone. I know there are differences in the cog width between Shimano and SRAM and also there are differences in the cog spacing between Shimano and SRAM and I think the KMC 9-speed chain is a closer match to the Shimano 9-speed cog set than it is to the SRAM 9-speed cog set. The SRAM worked but the Shimano just works better.

Any thoughts or comments are welcome.
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Old 05-27-14, 08:32 PM
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I don't believe there are any differences between Shimano and SRAM cog width or cog spacing, they use the same standards. I use them interchangeably.

There are differences between Campy and everyone else though.
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Old 05-27-14, 09:04 PM
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Per Sheldon Brown's site, Shimano and SRAM 9-speed cog spacing is identical. Cog thickness between Shimano & SRAM is the same for all practical purposes; there's only a 20 micrometer difference.
Code:
              SPACING     COG THICKNESS   SPACER THICKNESS   TOTAL WIDTH
Campagnolo    4.55 mm        1.75 mm          2.80 mm          38.2 mm
Shimano       4.34 mm        1.78 mm          2.56 mm          36.5 mm
SRAM          4.34 mm        1.80 mm          2.54 mm          36.5 mm
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