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Kinked cable inside Shimano ST-M050 shifter

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Kinked cable inside Shimano ST-M050 shifter

Old 11-22-16, 11:08 PM
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canklecat
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Kinked cable inside Shimano ST-M050 shifter

For the past few weeks I've been experiencing glitches downshifting the front derailer on the triple chain ring of my 1992 Univega. The upshift was fine, but on the downshift it would skip over the middle chainring en route from the largest to smallest.

First I cleaned the shifter by removing the dust cap and using some WD-40 and mineral spirits to clean out any congealed older lubes. The pawl seemed to move snappily and the sear surfaces were clean. With the cable de-tensioned the shifter seemed to function properly.

But the glitch continued.

So I removed the cable from the front derailer and redid all the usual adjusments from scratch. But the original cable position in the clamp and high/low limit settings all appeared to be appropriate.

And the glitch continued.

I finally pulled the cable from the housings and shifter to clean everything up and noticed a kink in the cable about an inch or so from the cable end stop. The kink was hidden inside the shifter. I tried to straighten the kink enough to get through a ride Sunday but the same shifting problem persisted.

At this point I'm assuming the kink is causing the problem. I would have thought the front derailer spring tension was enough to yank the cable past a slight kink but apparently not. So my next step is to replace the old cable and cable housing.

But before I replace it, can you think of any way the cable could have become kinked inside the shifter in normal installation and operation? I want to avoid this happening again. I have no idea who worked on the bike before -- I've had it only three months -- so I don't know whether this kink occurred sometime during normal operation of the bike or whether a DIY handyperson might have made a mistake.

Here's a diagram of the shifter.

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Old 11-22-16, 11:28 PM
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Because stuff happens on a bike that gets ridden? Andy
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Old 11-22-16, 11:50 PM
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True, dat.

I suppose I was hoping there was some other problem that wasn't immediately obvious. Although it's tough to beat a kinked cable hiding inside a shifter for not immediately obvious.
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Old 11-23-16, 09:00 AM
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Sometime that just happens. Although I see it more on old downtube shifters, it's not uncommon on newer ones. It could of happened during installation. Get some new ones, put them in carefully, and go ride.
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Old 11-23-16, 03:47 PM
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In retrospect my initial post was mostly just whining that it took three tries to finally figure out the problem.

I see Shimano has some universal cable and housing kits for brakes and shifters. Prices are reasonable. I'll just replace all the cables and housings. Probably about time for a 1992 bike. I got it in August and wasn't sure whether I'd like it well enough to want to put any money into it, but it's turned out to be my favorite bike the past couple of months. So I might as well treat it to new bits and pieces.
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Old 11-27-16, 05:43 PM
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Update: Replacing the cable didn't help.

Same problem downshifting. Upshifts are fine, smallest, middle to largest chain ring. But it won't shift properly from the largest to middle chain ring -- it skips down to the smallest ring.

There seems to be a hitch in the sear engagement. It appears fine with the dust cover and cable removed, without any tension. But it hangs when mounted and under tension.

I'll try soaking the shifter in mineral spirits. I've already squirted it generously with WD-40 and used cotton swabs with mineral spirits on all the accessible sear and pawl contact surfaces.

I'd like to keep this original Shimano thumb shifter set but it doesn't appear to be user friendly to disassemble for further servicing, beyond removing the dust cap.
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Old 11-27-16, 07:56 PM
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If the ratchets in the pod are hanging up from the TOO well discussed topic of gummy Shimano shifters it might take thinner and more solvent focused agents then mineral spirits to fully get into the pivots of the ratchets. I have serviced some pods where I had to remove the tiny "E" clip on the ratchet shaft and remove the pawl to completely clean the interface. Just watch where that E clip flies off to... Andy.
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Old 11-27-16, 10:55 PM
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Thanks, Andrew, I'll try a better solvent first. I remember reading about those flying bits from other threads discussing and cussing disassembling these shifters.

Do these shifters really need grease or will selective dabs of oil do as well?
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Old 11-28-16, 03:02 AM
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BTW, is there a friction shifter (like the Sunrace) I can use at least temporarily on the left side for the front derailer while I'm sorting out this shifter problem? Degunking the original shifter may take some time but I'd like to keep the bike rideable ASAP. And a friction shifter would help minimize the usual chain rub problems with triples.

The shifter pod can be detached from the brake assembly, although Shimano recommends against this for the ST-M050 and similar Rapidfires. That wouldn't leave much room for a replacement shifter, although one could conceivably fit between the outside edge of the lever assembly and end of the handlebar. And there's a small gap between the bar and plate where the shifter mechanism is attached.

If it's not possible to replace just the shifter I'd consider another shifter/brake (cantilever compatible) assembly for the left/front derailer.

Thanks again.
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Old 03-14-20, 03:06 PM
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Ditto

Hi, did you ever sort this out. I have just the same problem as you, I've taken all the same steps as you and still have the same problem.
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Old 11-06-20, 11:43 PM
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Originally Posted by Curzons246 View Post
Hi, did you ever sort this out. I have just the same problem as you, I've taken all the same steps as you and still have the same problem.
Sorry for the delay in responding -- nope, never did get those older Rapidfire shifters fixed. I switched the bike to albatross swept bars and Shimano bar-end shifters. The Rapidfire shifters are still in the closet. If I can find them I might try another squirt of solvent and lube and see if they'll work.
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Old 06-22-21, 12:48 AM
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Originally Posted by canklecat View Post
Sorry for the delay in responding -- nope, never did get those older Rapidfire shifters fixed. I switched the bike to albatross swept bars and Shimano bar-end shifters. The Rapidfire shifters are still in the closet. If I can find them I might try another squirt of solvent and lube and see if they'll work.
I ended up taking the right shifter apart. Let me tell ya, it took so long to put back together. I can do the whole thing now in a few minutes. The set I had were not gummed up but more like solidified. Granted I got impatient. What I would do next time is make sure I have top bottom established on each layer and N, S, E, W for each layer. Once ya mess with it for a while and look at the pictures youb will take before and during disassembly, it will start to make sense.
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