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Old 07-26-13 | 06:27 PM
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FBinNY
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Joined: Apr 2009
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From: New Rochelle, NY

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

OK, there's no official name, but I call this a spanning problem. Namely, the total range of travel end to end is too much or too little and a cumulative error gets greater from one end to the other.

The most obvious cause is the number of shifts not matching, ie. 10s lever, 9s cassette. It also happens if the cassette spacing is not matched, ie Campagnolo cassette/shimano derailleurs, or using mtn levers for a road derailleur.

Start by shifting to your 2nd high gear, and trimming the RD perfectly centered under the sprocket. Now shift all the way to low. If it won't shift, help it by pushing in the lower body to complete the shift, then let go and see if it holds it. Eyeball how far off the trim is, and if it's more than 1mm, odds are something is mis-matched. (reminder, a 9s lever has 8 clicks, or start + 8 shifts make 9).

Check, for brand/model spec. compatibility all the way up the line.

The other cause for spanning errors, but usually of less than 1mm end to end, is worn housing, or end fittings that are sloppy or misaligned. As the spring tension increases, you get some compression or lost travel in the cable.

You can also bet spanning errors if the hanger is misaligned, but it has to be petty bad, and I'd expect you'd have noticed it. A quick check for hanger alignment is to shift and trim for a middle cassette sprocket, then shift the front. If the rear trim changes, even by a little bit, the hanger isn't straight.
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