I have a bit of a dilemma concerning my Shimano XTR m-960 shifter/brake lever. Some time ago I wiped out and snapped off the index finger shifter head. There was enough of a nubbin left that I was able to continue using the shifter without much issue. Still, it was something I intended to fix when time and funds allowed. I managed to purchase what appeared to be a very lightly used pair of XTR shifter/brakes at VeloSwap and have been sitting on them for a while. After the pin that secures the brake lever popped out of the left-hand shifter, I decided it was time to swap out the units and have a fresh set on the bike. An easy-enough chore.
As it turns out, the “new” right-side shifter — the one that was replacing the one with broken lever — does not ratchet through the full range under tension. It manages about five clicks and then goes limp. I presume that this is why the putz who sold them did so with no warning. So, I thought that I might be able to disassemble it, get the lever out and re-install that in my old unit, which is still perfectly functional.
No dice. I can’t figure out how to even get the assembly out of the body, much less disassemble it and put it all back together. Could be a Humpty Dumpty scenario if I don’t get some guidance.
My question to you: Is there hope here or are my options to either continue using the old unit or to simply buy a new one? Are there any detailed instruction manuals available that could guide me through the disassembly/reassembly process or would it be best to take it to a shop?
If you look on Shimano’s page of downloadable mountain bike component manuals you will find, under “ST Dual Control Levers,” your ST-M960 levers. If you download the first file you’ll notice that the shifter units, numbered “1″ in the figures, are the entire main assemblies.
Shimano offers neither parts nor instructions for dismantling the shifter units themselves.
This applies to road dual control levers as well as to mountain bike ones. The units are assembled by robots and Shimano has no interest in human beings taking them apart and putting them back together. I have tried overhauling Shimano STI road levers, since Campagnolo and SRAM levers are fairly friendly to the home mechanic, but I failed miserably and gave up on putting them back together. There are simply too many tiny springs and parts requiring special tools to install them and tighten them down. I tried to make some tools with which to grab strangely shaped parts or to compress the springs and line them up with the holes they need to go in, but to no avail. I would guess that this is the sort of thing you’d encounter in these M960 levers as well.
Judging by my experience with Campagnolo levers that exhibit the behavior you describe, there is probably either just a return spring out of place or there is a tooth not engaging between an index gear and a lever tip that advances it or stops it from advancing. The return spring issue on a Campy lever is easy to remedy without even disassembling the lever; you just push the spring end back in place. So it’s worth staring at that piece you have to see if you see the end of a return spring that is not in its notch. If you do, see if you can push it back into place with a sharp implement. If there is a tooth not engaging, whether the parts are out of place or broken, I don’t think there will be anything you can do about it on a Shimano lever.
Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
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